The conversion of light energy into mechanical energy for directed photoactuation is a goal that has been pursued for decades. This work has led to azobenzene liquid-crystal polymers (LCPs), which demonstrate photo-activated bending when irradiated with UV or blue-green light. This intriguing phenomenon has potential to significantly impact the fields of Lab-on-a-Chip, MEMS and soft robotics, but the jump into practical application requires precise fabrication of azobenzene-based structures capable of being leveraged into useful and efficient photomechanical work. Three such configurations have been designed to this end: azobenzene films patterned by soft lithography, azobenzene nanofibers and azobenzene nanobeads.
Sustained delivery of growth factors, proteins, drugs and other biologically active molecules is necessary for tissue engineering applications. Electrospun fibers are attractive tissue engineering scaffolds as they partially mimic the topography of the extracellular matrix (ECM). However, they do not provide continuous nourishment to the tissue. In search of a biomimetic scaffold for salivary gland tissue regeneration, we previously developed a blend nanofiber scaffold composed of the protein elastin and the synthetic polymer polylactic-co-glycolic acid (PLGA). The nanofiber scaffold promoted in vivo-like salivary epithelial cell tissue organization and apicobasal polarization. However, in order to enhance the salivary cell proliferation and biomimetic character of the scaffold, sustained growth factor delivery is needed. The composite nanofiber scaffold was optimized to act as a growth factor delivery system using epidermal growth factor (EGF) as a model protein. The nanofiber/EGF hybrid nanofibers were synthesized by double emulsion electrospinning where EGF is emulsified within a water/oil/water (w/o/w) double emulsion system. Successful incorporation of EGF was confirmed using Raman spectroscopy. EGF release profile was characterized using enzyme-linked immunosorbent assay (ELIZA) of the EGF content. Double emulsion electrospinning resulted in slower release of EGF. We demonstrated the potential of the proposed double emulsion electrospun nanofiber scaffold for the delivery of growth factors and/or drugs for tissue engineering and pharmaceutical applications.
Non-invasive live cell measurements are an important tool in biomedical research. We present a combined digital holography/Raman spectroscopy technique to study live cell cultures during apoptosis. Digital holographic microscopy records an interference pattern between object and reference waves, so that the computationally reconstructed holographic image contains both amplitude and phase information about the sample. When the phase is mapped across the sample and converted into height information for each pixel, a three dimensional image is obtained. The measurement of live cell cultures by digital holographic microscopy yields information about cell shape and volume, changes to which are reflective of alterations in cell cycle and initiation of cell death mechanisms. Raman spectroscopy, on the other hand, is sensitive to rotational and vibrational molecular transitions, as well as intermolecular vibrations. Therefore, Raman spectroscopy provides complementary information about cells, such as protein, lipid and nucleic acid content, and, particularly, the spectral signatures associated with structural changes in molecules. The cell cultures are kept in the temperature-controlled environmental chamber during the experiment, which allows monitoring over multiple cell cycles. The DHM system combines a visible (red) laser source with conventional microscope base, and LabVIEW-run data processing. We analyzed and compared cell culture information obtained by these two methods.
KEYWORDS: Tumors, In vitro testing, In vivo imaging, Microfluidics, Etching, Glasses, Content addressable memory, Cancer, Quantitative analysis, Scanning electron microscopy
The NANIVID – or Nano Intravital Device – is an implantable delivery tool designed to locally affect the tumor microenvironment in vivo. This technology is being redesigned and validated as a cell collection tool for the study of metastatic cancer cells. A methodology has been developed to facilitate this transition, consisting of microfluidic analysis of the device microchannels and a series of cell-related collection experiments building up to in vivo collection. Single-chamber designs were first used to qualitatively demonstrate the feasibility of cell collection ex vivo. This was followed by the development and implementation of devices containing a second, negative-control chamber for quantitative analysis. This work sets the foundation for in vivo cancer cell migration studies utilizing the NANIVID.
The tumor microenvironment is a complex system which is not fully understood. New technologies are needed to provide a better understanding of the role of the tumor microenvironment in promoting metastasis. The Nano Intravital Device, or NANIVID, has been developed as an optically transparent, implantable tool to study the tumor microenvironment. Two etched glass substrates are sealed using a thin polymer membrane to create a reservoir with a single outlet. This reservoir is loaded with a custom hydrogel blend that contains selected factors for delivery to the tumor microenvironment. When the device is implanted in the tumor, the hydrogel swells and releases these entrapped molecules, forming a sustained concentration gradient. The NANIVID has previously been successful in manipulating the tumor microenvironment both in vitro as well as in vivo. As metastatic cells intravasate, it has been shown that some are able to do so unscathed and reach their new location, while others are cleaved during the process1. There appears to be a correlation between cell migration and the mechanical properties of these cells. It is believed that these properties can be detected in real time by atomic force microscopy. In this study, metastatic MTLn3 rat mammary cells are seeded onto 1-dimensional microfibers and directed up a stable gradient of growth factor. The NANIVID device is placed behind our AFM tip, where it generates a stable chemotactic gradient of epidermal growth factor. Scanning confocal laser microscopy is also used to monitor movement of the cells over time. This experiment will shed light on the mechanical changes in metastatic cells as they undergo directed migration.
Monitoring the presence of nanomaterials in waste water from semiconductor facilities is a critical task for public health
organizations. Advanced semiconductor technology allows the fabrication of sensitive piezoelectric-based mass sensors
with a detection limit of less than 1.35 ng/cm2 of nanomaterials such as nanoparticles of alumina, amorphous silica,
ceria, etc. The interactions between acoustic waves generated by the piezoelectric sensor and nanomaterial mass
attached to its surface define the sensing response as a shift in the resonant frequency. In this article the development and
characterization of a prototype AlN film bulk acoustic resonator (FBAR) are presented. DC reactive magnetron
sputtering was used to create tilted c-axis oriented AlN films to generate shear waves which don’t propagate in liquids
thus minimizing the acoustic losses. The high acoustic velocity of AlN over quartz allows an increase in resonance
frequency in comparison with a quartz crystal microbalance (QCM) and results in a higher frequency shift per mass
change, and thus greater sensitivity. The membrane and electrodes were fabricated using state of the art semiconductor
technology. The device surface functionalization was performed to demonstrate selectivity towards a specific
nanomaterial. As a result, the devices were covered with a “docking” layer that allows the nanomaterials to be selectively
attached to the surface. This was achieved using covalent modification of the surface, specifically targeting ZnO
nanoparticles. Our functionalization approach was tested using two different types of nanoparticles, and binding
specificity was confirmed with various analytical techniques.
Multiple changes within the tumor microenvironment have been correlated with an increase in metastasis, yet the mechanisms are not fully understood. Tumor cells can be stimulated by the release of chemoattractant factors such as epidermal growth factor (EGF) from nearby stromal cells, resulting in increased intravasation and metastasis. Additionally, altered extracellular matrix density can result in changes in gene expression patterns governing increased cellular proliferation and motility. The Nano Intravital Device (NANIVID) has been used to produce gradients of select soluble factors in the tumor microenvironment and to study the role of these changes on cell migration. In previous studies, the NANIVID utilized a synthetic hydrogel to produce an EGF gradient to attract metastatic breast cancer cells. In this work, a matrigel insert will be introduced into the outlet to provide a substrate for cells to migrate on when entering the device. The concentration of the chemoattractant and matrigel comprising the insert will be optimized to produce a suitable gradient for inducing chemotaxis in metastatic breast cancer cells in vitro. Additionally, silk and alginate matrices will be explored as improved soluble factor release mediums. Delivery of larger molecules such as collagen cross-linkers requires an alternative hydrogel material. Future NANIVID experiments will utilize these materials to gauge the cellular motility response when a stiffer matrix is encountered.
Cancer cells create a unique microenvironment in vivo that enables migration to distant organs. To better understand the tumor microenvironment, special tools and devices are required to monitor the interactions between different cell types and the effects of particular chemical gradients. Our study presents the design and optimization of a versatile chemotaxis device, the nano-intravital device (NANIVID), which consists of etched and bonded glass substrates that create a soluble factor reservoir. The device contains a customized hydrogel blend that is loaded with epidermal growth factor (EGF), which diffuses from the outlet to create a chemotactic gradient that can be sustained for many hours in order to attract specific cells to the device. A microelectrode array is under development for quantification of cell collection and will be incorporated into future device generations. Additionally, the NANIVID can be modified to generate gradients of other soluble factors in order to initiate controlled changes to the microenvironment including the induction of hypoxia, manipulation of extracellular matrix stiffness, etc. The focus of the article is to present the design and optimization of the device towards wide ranging applications of cancer cell dynamics in vitro and, ultimately, implantation for in vivo investigations.
The Nano Intravital Device, or NANIVID, is under development as an optically transparent, implantable tool to study
the tumor microenvironment. Two etched glass substrates are sealed using a thin polymer membrane to create a reservoir
with a single outlet. This reservoir is loaded with a hydrogel blend that contains growth factors or other chemicals to be
delivered to the tumor microenvironment. When the device is implanted in the tumor, the hydrogel will swell and release
these entrapped molecules, forming a gradient. Validation of the device has been performed in vitro using epidermal
growth factor (EGF) and MenaINV, a highly invasive, rat mammary adenocarcinoma cell line. In both 2-D and 3-D
environments, cells migrated toward the gradient of EGF released from the device. The chorioallantoic membrane
(CAM) of White Leghorn chicken eggs is being utilized to grow xenograft tumors that will be used for ex vivo cell
collection. Device optimization is being performed for in vivo use as a tool to collect the invasive cell population.
Preliminary cell collection experiments in vivo were performed using a mouse model of breast cancer. As a second
application, the device is being explored as a delivery vehicle for chemicals that induce controlled changes in the tumor
microenvironment. H2O2 was loaded in the device and generated intracellular reactive oxygen species (ROS) in cells
near the device outlet. In the future, other induction targets will be explored, including hypoglycemia and the
manipulation of extracellular matrix stiffness.
Cancer cells create a unique microenvironment in vivo which enables migration to distant organs. To better understand
the tumor microenvironment, special tools and devices are required to monitor the interactions between different cell
types and the effects of particular chemical gradients. This study presents the design and optimization of a new, versatile
chemotaxis device called the NANIVID (NANo IntraVital Device). The device is fabricated using BioMEMS techniques
and consists of etched and bonded Pyrex substrates, a soluble factor reservoir, fluorescent tracking beads and a
microelectrode array for cell quantification. The reservoir contains a customized hydrogel blend loaded with EGF which
diffuses out of the hydrogel to create a chemotactic gradient. This reservoir sustains a steady release of growth factor
into the surrounding environment for many hours and establishes a concentration gradient that attracts specific cells to
the device. In addition to a cell collection tool, the NANIVID can be modified to act as a delivery vehicle for the local
generation of alternate soluble factor gradients to initiate controlled changes to the microenvironment such as hypoxia,
ECM stiffness and etc. The focus of this study is to design and optimize the new device for wide ranging studies of
breast cancer cell dynamics in vitro and ultimately, implantation for in vivo work.
Metastatic cancer cells respond to chemical and mechanical stimuli in their microenvironment that guide invasion into
the surrounding tissue and eventually the circulatory/lymph systems. The NANIVID is designed to be an in vivo device
used to collect metastatic cancer cells by providing a gradient of epidermal growth factor through the controlled release
from a customized hydrogel. The model cells, MTLn3 and MenaInv, both derived from a rat mammary adenocarcinoma,
will migrate toward the device and be collected in the chamber. A set of electrodes inside the chamber will provide real-time
data on the density of cells collected in the device. The characterization and optimization of the electrodes in vitro
will be reported, as will the development of an equivalent circuit model used to describe electrode behavior. The ultimate
goal of this work is for the NANIVID to be used for in vivo investigations of a rat model of mammary cancer.
Furthermore, since the morphology, mechanical properties, and movement of cells are influenced by the
microenvironment, a combined scanning confocal laser microscope and atomic force microscope will be used to study
these relationships. This work will further the understanding of the dynamics and mechanics of metastatic cancer cells as
they leave the primary tumor and metastasize.
In-vivo cancer cells create a unique microenvironment which enables their spread to other organs. To understand the
tumor microenvironment, special tools and devices are required to monitor the interaction among different cell types as
well as the effects of particular chemical gradients. We are reporting on the status of a new device (the NANIVID:
NANoIntraVItal Device) that will collect chemotactic cells from the tumor environment. Due to the transparency of this
implantable device, direct in-vivo cell imaging both inside and outside the device is possible. The cell collection chamber
of the device consists of a micro-electrode system based on patterning of transparent, conducting films that deliver real
time data including cell density and dynamics. The current development and testing status of the device will be
presented. This will include the modeling of ligand gradient profile results produced from the device and the cell
migration in the EGF (epidermal growth factor) gradient created by the device. Further, prototype electrode arrays were
designed, fabricated and cells were cultured on the arrays at selected degrees of confluence to measure the device
sensitivity. The development path of the NANIVID will be integrated with an existing animal model protocol for in-vivo
testing. This will result in a clearer understanding of the dynamics of a tumor's metastatic progression.
The Tumor MicroEnvironment for Metastasis (TMEM) is a critical determinant which will presage the evolution of
primary tumors and the resulting metastatic dynamics. Primary tumor cells up and down regulate certain genes which
increase motility and cause a disregard for positional information. We report on the development of a new tool for the
documentation of cancer cell migration (initial targets: the rat mammary adenocarcinoma cell lines MTLn3 with an over
expression of Mena+++). This tool, the NANo IntraVital Device (NANIVID), is a multi-functional nanosystem
composed of a chemoattractant source (hydrogel-EGF), capsule (cell trap), counter (transparent, interdigitated electrode
arrays for sensing cell arrival), and remote reporter (readout electronics). The device will be retrieved from the tumor
site and the cells will be expelled for subsequent assay. The NANIVID will be used in conjunction with the current
catheter-based approach in which a needle is loaded with a chemoattractant source and injected into the tumor. A major
drawback in the catheter approach is the short cell collection time and lack of real time registering and reporting of cell
arrival. This paper will present the current status of the NANIVID prototypes developed in which a transparent
implantable device is loaded with chemoattractant source and placed near candidate mammary gland tumors in an
established rat model for multiple days or weeks. This series of experiments will allow the comparison of methods and
to benchmark the NANIVID for use in research. Initial results of these experiments and NANIVID design modifications
will be presented.
Microfluidic devices are currently being utilized in many types of BioMEMS and medical applications. In
these systems, the interaction between the surface and the biological specimen depends critically on surface properties.
The surface roughness and chemistry as well as the surface area to which the biomolecules or cells are exposed affect
this interaction. Modification of the surface of microfluidic channels can improve the operation of the device by
influencing the behavior of the biological specimens that are flowing through it. SU-8 is an epoxy-based, negative
photoresist that has been previously used to create covered channels. Once cured, it is both chemically and thermally
stable. It is also optically transparent above 360 nm, which allows optical measurements, including fluorescence
imaging, to be taken inside the channel. SU-8 microchannels have been fabricated with a porous layer on the sidewalls
by the photo-lithographic process, which is reproducible with precisely controlled channel dimensions. In order to attain
these porous sidewalls, no additional fabrication steps are required outside the standard photo-lithographic process. The
porosity of the sidewalls is a result of incomplete cross-linking of the polymer. The obtained porous surfaces can be
specially treated to provide conditions preferable for biological interactions. The porous layer increases the internal
surface area available on the sidewalls, which make these microfluidic channels preferable for biological applications.
This paper describes the details of the fabrication process and the experiments that verify the benefit of using SU-8
microchannels with porous sidewalls.
Optical interferometry is a well established technique for high resolution displacement measurements. It is commonly used in the semiconductor industry as a sub-system of manufacturing and metrology tools. As the industry progresses, the tools continue to evolve, requiring the concomitant reduction of size and cost in sensors. Existing interferometric systems are bulky and therefore difficult to incorporate in equipment. Efforts are ongoing to miniaturize these systems but with optical components (beam splitters, detectors and lasers) still in the millimeter range, it is difficult to realize ultra compact systems. Thus, it is imperative to focus on development of micron scale components that would provide the necessary high spatial resolution in a compact format.
The focus of this paper is on the development of a micron size optical component that combines multiple optical elements and can be integrated with VCSELs at the wafer level to yield a compact, low cost interferometric system. The design and development of this component containing the beam splitter and reference mirror will be presented including the investigation of suitable polymeric materials with desirable optical properties and appropriate fabrication techniques. Preliminary optical measurements of the integrated system will also be demonstrated. This approach has the potential to impact the next generation of micron scale interferometers as precise position/proximity sensors.
We describe two types of active optical devices developed for
use as free-space optical interconnects FSOIs for chip-to-chip communications.
The design of both types of devices—membrane and freestanding
structures—includes both optical and mechanical components.
The optical component contains porous silicon PSi with customized
optical properties fabricated by electrochemical etching of silicon. The
mechanical part of the devices is composed of metal/nitride bimorph
thermal actuators. The membrane devices form concave mirrors when
actuated, and can be used to focus the incoming optical signals and
correct any optical misalignment within the input/output I/O fabric. The
freestanding devices have out-of-plane optical components, whose tilting
angle is controlled by the current applied to the actuator. These devices
can function as either reflectors or tunable optical filters. By incorporating
the developed PSi diffractive optical element DOE into the freestanding
structure, another type of freestanding device is realized for beamsplitting
applications. Details of the fabrication, testing, and integration of
these PSi-based devices are presented.
Cancerous tumors are dynamic microenvironments that require unique analytical tools for their study. Better
understanding of tumor microenvironments may reveal mechanisms behind tumor progression and generate new strategies for diagnostic marker development, which can be used routinely in histopathological analysis. Previous studies have shown that cell invasion and intravasation are related to metastatic potential and have linked these activities to gene expression patterns seen in migratory and invasive tumor cells in vivo. Existing analytical methods for tumor microenvironments include collection of tumor cells through a catheter needle loaded with a chemical or protein attractant (chemoattractant). This method has some limitations and restrictions, including time constraints of cell collection, long term anesthetization, and in vivo imaging inside the catheter. In this study, a novel implantable device was designed to replace the catheter-based method. The 1.5mm x 0.5mm x 0.24mm device is designed to controllably release chemoattractants for stimulation of tumor cell migration and subsequent cell capture. Devices were fabricated using standard microfabrication techniques and have been shown to mediate controlled release of bovine serum albumin (BSA) and epidermal growth factor (EGF). Optically transparent indium tin oxide (ITO) electrodes have been incorporated into the device for impedance-based measurement of cell density and have been shown to be compatible with in vivo multi-photon imaging of cell migration.
Porous silicon (PSi) is a promising material for the creation of optical components for chip-to-chip interconnects because
of its unique optical properties, flexible fabrication methods and integration with conventional CMOS material sets. In
this paper, we present a novel active optical filter made of PSi to select desired optical wavelengths. The tunable
membrane type optical filter is based on a Fabry-Perot interferometer employing two Bragg reflectors separated by an
adjustable air gap, which can be thermally controlled. The Bragg reflectors contain alternating layers of high and low
porosities. These layers were created by electrochemical etching of p+ type silicon wafers by varying the applied current
during etching process. Micro bimorph actuators are designed to control the movement of the top DBR mirror, which
changes the cavity thickness. By varying the applied current, the proposed filter can tune the transmitted wavelength of
the optical signal. Various geometrical shapes and sizes ranging from 100μm to 1mm of the active filtering region have
been realized for specific applications. The MOEMS technology-based device fabrication is fully compatible with the
existing IC mass fabrication processes, and can be integrated with a variety of active and passive optical components to
realize inter-chip or intra-chip communication at the system level at a relatively low cost.
With the continued miniaturization and sophistication of current generations of semiconductor devices, it is the
limitations of data transfer rates that are beginning to impact system performance. Although conventional pathways
continue progressing, researchers are moving toward optical interconnects as a potential solution. Optical
interconnection is a promising way to replace existing global or chip-to-chip interconnects in future integrated
circuits. In contrast to existing metallic wiring, optical interconnects exhibit smaller distance-related loss or
distortion of the signal, no deleterious fringing effects and no heat dissipation in the interconnect itself.
Pioneering interconnect schemes are currently being developed using both planar waveguides and fibers to distribute
optical signals around printed circuit boards. However, researchers are now attempting to incorporate novel, freespace
optical interconnects, which will boost data transfer rates by a factor of a thousand. These systems consist of
a number of components including vertical cavity surface emitting lasers (VCSELs), lenses, diffractive optical
elements and detectors. Integration of single components into sub-systems will help to minimize the optical system
footprint for both on-chip and chip-to-chip interconnects.
This paper will present the development of both independent and integrated with VCSELs,static diffractive optical
element (DOEs) made of SU8 and prove the feasibility of such an approach. SU8 is a negative tone photoresist,
conventionally used for high aspect ratio MEMS-based structures. Recent developments in thin film SU8 along
with its low absorption at long wavelengths makes it a suitable material for optical applications. By developing a
low cost lithography based process, SU-8 DOEs can be efficiently integrated directly on laser sources with minimal
effect to VCSEL performance. This approach could have a significant impact on the creation of next generation
optical I/O fabrics.
Among the major challenges confronting the current initiatives to incorporate optical interconnect capabilities for
chip to chip I/O is to define, develop and implement the necessary components required for a complete pipeline
from source to receiver. For next generation integrated circuits, the need for multifunctionality and multidimensional
integration has resulted in new demands on interface technology to yield massively parallel data and
clock lines. At this point, such methods are primarily limited to static reflectors, filters and gratings for interface
and optical routing. One of the crucial elements is to develop a high performance and flexible optical network to
transform an incoming optical pulse train into a widely distributed set of optical signals whose direction, alignment
and power can be independently controlled. This coupling can be achieved using several methods including active
(primarily, MEMS-based) beam steering arrays. For chip to chip applications, the overwhelming majority of the
recent research and development effort has been focused on source and detector technologies, but less attention
has been devoted to flexible, reconfigurable beam steering modalities. A variety of approaches for such beam
steering and distribution of both timing and data lines has been examined. This paper will present an overview of
active, silicon components under development at the College of Nanoscale Science and Engineering for arraybased
I/O management with an emphasis on reconfigurable diffractive devices and adjustable, porous silicon-
based components which combine optical beam steering, filtering and focusing capabilities. Design details along
with initial performance data from prototype components will be presented.
Porous silicon (PSi) is an attractive material for fabrication of multilayer optical devices such as Bragg
reflectors, Fabry-Perot resonators and other novel (optical) components. Such devices are characterized by a
periodic modulation of the refractive indices in alternating layers and can be classified as 1D photonic crystals. 2D
photonic bandgap structures can be also obtained using a variation of applied potential on the back side of the
sample during electrochemical formation of the multilayers. This technique allows a fabrication of spatially
distributed filters on the millimeter size scale. In this paper, a new method is presented which uses a front side
protective mask for the creation of 2D photonic bandgap structures on the micron scale. The devices obtained by this
technique can be used for the creation of spatially distributed filters. The front side protective mask controls lateral
undercut in multiple ways depending on the mask material. By varying the design and material of the protective
mask, PSi interference filters with desired optical parameters across a field of view can be realized.
In this paper, a novel, simple method to produce 2D periodic multilayer structures is described. In
particular, the focus is on the changes in the photonic crystal cavities when various mask materials are used. In
addition, a new type of active optical components for a chip-to chip interconnection based on the combination of our
method and MEMS technology is presented.
Although conventional optical lever technology typically used for scanning probe microscope applications has proven high sensitivity, accuracy, and is cost effective for most applications involving micromachined cantilever deflection measurements, the frequency limitations and space needs limit its applicability to emerging ultrasonic-based scanning probe microscopy (SPM) applications. Recently, the fabrication of cantilevers integrated with actuation and sensing components has opened avenues for feedback-based driving of micromachined cantilevers at higher order resonance frequencies, while sensing average deflection without the need of an optical deflection pathway for average deflection sensing. The work presented here reviews recent efforts by our group in fabricating micromachined cantilevers with integrated ZnO actuation layers to induce cantilever deflection. These cantilevers are being fabricated for use in a heterodyne force microscopy system (HFM) to enable SPM imaging contrast based on viscoelastic response of a surface in contact with a micromachined tip, wherein active-feedback technology is being applied to maintain ultrasonic tip excitation at higher order cantilever resonances. The first- and second-pass fabrication results are presented and reviewed regarding cantilever release and ZnO actuator (and electrode) fabrication. Dynamic response data from these structures, measured via laser Doppler vibrometry, reveal the expected resonance structure for a cantilever of these dimensions.
We focus on the development and fabrication of SU8TM-based microchannel networks, which can be integrated into microdevices for fast drug delivery and cell transport on chips. Instead of using sacrificial materials or wafer bonding, a new simplified fabrication method is developed. Single- and double-layered SU8TM channels on silicon substrates are successfully achieved by using this new method, as well as integration of these SU8 channels with microelectrode arrays. A series of cell transport experiments is also successfully performed on these devices. This new fabrication approach and the resulting cell transport experiments are discussed in detail.
To assist the growth of the telecommunication sector, new types of optical components such as those based on optical interference filter technology are critical. Existing technologies based on thin-film processing for production of optical communications filters have rapidly advanced. Although the Fabry-Perot bandpass filters made by deposition of alternate layers with high- and low- refractive index have a broad rejection band and a narrow passband, this technique does not allow for the control of filter parameters such as specification and adjustment of the transmitted wavelength at any place across the surface of the filter. The new approach discussed in the paper is directed toward the anodization of silicon to fabricate not only multilayer optical filters with a uniform passband across the field of view but also specially designed passbands at any single point in the field of view of the optical system. In particular, the realization and characterization of spatially distributed filters made of porous silicon are presented. These filters are able to select various passbands in the visible and IR regions. The filters were fabricated on p+ and p - type doped substrates. By varying the electrode configuration on the backside of wafer and the applied potential during electrochemical etching, the desired spatially distributed filter can be formed. The impact of wafer resistivity on filter parameters is discussed.
The use of miniaturized optical components for chip level communications is increasing rapidly. The possible applications include: optical switching, signal monitoring, I/O reconfiguration, and add/drop multiplexing. Micro-Opto-Electro-Mechanical Systems (MOEMS) based on customized IC fabrication processes are being used to assemble system-level architecture for integration into mainstream circuitry. MOEMS devices based on dynamic diffractive elements are currently investigated for both their signal routing capabilities and de-multiplexing properties. These characteristics are expected to increase the speed of optical data transfer. This paper focuses on the current status of the MOEMS research program for Free Space Optical inter-chip communication at the College of Nanoscale Science and Engineering, University at Albany- SUNY (CNSE) based on the MEMS Compound Grating (MCG) design. Operational characteristics of these MCG devices have been shown to operate at high voltages (>15V) compared to 5V levels prevalent in conventional integrated circuits. The specific goal of this work is to improve performance while minimizing power consumption. A design change that incorporates a higher capacitance and a lighter suspension system has been studied. A new fabrication process has been constructed utilizing Polyimide as a structural material. Fabrication steps have been optimized for best MCG device performance. Experimental results from both research tasks will be presented.
The pressure for reduction in cost and development time in new product, together with the need to pack more functions into smaller volumes in silicon chips has been fueling the system-on-chip (SOC) development. However, the current SOC technologies available essentially involve merging of chips fabricated with standard CMOS technology. These SOC technologies provide an integration solution with compatible fabrication processes that require little changes in process integration. There is no standard cost-effective solution to make 3D MEMS and optoelectronic devices together with CMOS on the same chip without compromising material compatibility, process complexity and system performance. One solution is to fabricate MEMS and CMOS components on separate wafer substrates and then stack them together with well isolated interconnected vias. In order to demonstrate this wafer-level 3D integration technology, a novel wafer-level bonding technology is being developed. This paper reports a detailed study of 3D MEMS (Micro Electro-Mechanical Systems) integration through multi-wafer anodic and polymeric wafer bonding. Different from previously reported wafer bonding studies, this study focuses on the optimization of the bonding process to improve the bonding quality.
The eventual widespread insertion of microoptoelectromechanical systems (MOEMS) into the marketplace rests fundamentally on the ability to produce viable components that maximize optical performance while minimizing power consumption and size. Active control of surface topology allows for one component to perform multiple functions, thus reducing cost and complexity. Based on the patented MEMS compound grating (MCG), extension of the research at the College of Nanoscale Science and Engineering (CNSE) at the University of Albany, New York, to novel designs, materials, and fabrication methods yielded low-power, high-performance prototypes. The main focus of this work is on the development of a polymer version (including a sacrificial layer, in some designs) of the MCG, which allows for ease of fabrication and a reduced electrostatic actuation voltage. Following a system design effort, several generations of the component are fabricated to optimize the process flow. Component metrology, electromechanical characterization, and initial results of optical tests are reported. A second example presented is the design and prototype fabrication of a spring micrograting using a customized SOI process. This highly flexible component builds on the MCG concept and yields an order of magnitude reduction in actuation voltage.
Solar cells based on organic and inorganic materials are an emerging technology for a new generation of photovoltaics (PV). Hybrid solar cells, which use both organic and inorganic components, have advantages such as cost-effective processing and the ability to fabricate devices on flexible substrates. The combination of organic materials with semiconductor nanostructures allows enhancement of the conversion efficiency due to the fast electron transport in semiconductors and a high interface area between organic and inorganic components. In our work, anodized porous Si (PSi) was chosen as a host matrix filled with Copper Phthalocyanine (CuPC) molecules. The resulting nanocomposite can yield high performance novel materials for solar cells.
The fabrication of PSi was completed using electrochemical etching of Si in diluted hydrofluoric acid (HF). Also, this process, with some modifications, can be applied to produce free-standing PSi films of desired thickness. PSi layer was filled with CuPC dissolved in concentrated sulfuric acid. The top contact was made by sputtering of Au or ITO. A power conversion efficiency (PCE) of 3% (33 mW/cm2) was obtained for 12 um thick n-type pSi layer with pore sizes of approximately 15 nm filled with CuPC. The electrochemical etching of Si under different conditions was carried out to optimize the photovoltaic parameters. A detailed investigation of the solar cell performance depending on porous layer thicknesses and pore sizes is presented. The use of free-standing films of PSi can lead to the fabrication of novel PV solar cells on flexible substrates with high conversion efficiency.
Micromachined cantilevers used as force probes in atomic force microscopy are extremely sensitive to a variety of environment factors such as acoustic noise, temperature and humidity. This unwanted interference can be exploited to produce highly sensitive systems with proper design and under precise conditions. In this paper, we report the development of a new generic process for the fabrication of a microprobe with integrated piezoresistive read-out and built-in piezoelectric actuators. The mechanical performance of cantilever probes of various dimensions was studied. The result from the Finite Element Analysis (FEA) was compared to the experimental results. Application of this probe in a nondestructive, general-purpose, near-field nanomechanical imaging system will be discussed.
This paper focuses on the development of two MEMS-based devices for lab-on-a-chip bio-applications. The first device is designed to facilitate cell secretion studies by enabling parallel electrochemical detection with millisecond resolution. Initial prototypes of micro-arrays have been fabricated with Cr/Au microelectrodes on various substrates such as polyimide, SU-8 and SiO2. An FT cell-line (bullfrog fibroblast, American Tissue Culture Collection) has been successfully established and cultured directly on these prototype micro-arrays. It is well known that the FT cells can uptake hormones or other macromolecules from the culture media through a non-specific uptake mechanism which is still under investigation. After culturing on micro-arrays, FT cells were loaded with norepinephrine of various concentrations by incubation in the culture media supplied with norepinephrines. Rapid elevation of intracellular Ca2+ levels triggers the exocytosis of norepinephrine which then can be detected by the Cr/Au electrodes. Microfabrication of these prototype micro-arrays as well as cell culture and electrochemical detection results will be presented in this paper. The second device is designed for 3-dimensional transportation of living cells on chips. Initial prototypes of micro-arrays were fabricated with SU-8 buried channels on a silicon substrate. Both single-layered and double-layered SU-8 buried channels have been realized to enable 2D and 3D cell transportation. Stained solutions were used to visualize fluid transport through the channel networks. Following this, living FT cells in solution were successfully transported through single-layered SU-8 channels. Testing of 3D transportation of living FT cells is underway. Microfabrication of these prototype micro-arrays and living cell transportation on chips will also be presented in this paper.
Micro-Opto-Electro-Mechanical Systems (MOEMS) have found a variety of applications in fields such as telecommunications, spectroscopy and display technology. MOEMS-based optical switching is currently under investigation for the increased flexibility that such devices provide for reconfiguration of the I/O network for inter-chip communication applications. This potential not only adds an additional degree of freedom for adjustment of transmitter/receiver links but also allows for fine alignment of individual channels in the network link. Further, this use of diffractive arrays for specific applications combines beam steering/adjustment capabilities with the inherent wavelength dependence of the diffractive approach for channel separation and de-multiplexing. Research and development has been concentrated on the progression from single MOEMS components to parallel arrays integrated with optical source arrays for a successful feasibility demonstration. Successful development of such an approach will have a major impact of the next generation communication protocols.
This paper will focus on the current status of the MOEMS research program for Free Space Optical inter-chip communication at the College of NanoScale Science and Engineering, University at Albany-SUNY (CNSE). New versions of diffractive arrays stemming from the basic MEMS Compound Grating (MCG; patent #5,999,319) have been produced through various fabrication methods including the MUMPs process1. Most MEMS components relying on electrostatic actuation tend to require high actuation voltages (>20V) compared to the typical 5V levels prevalent in conventional integrated circuits. The specific goal is to yield improved performance while minimizing the power consumption of the components. Structural modifications through the variation in the ruling/electrode spacing distance and array wiring layout through individually addressable gratings have been studied to understand effects on the actuation voltage and cross talk, respectively. A detailed overview of the optical and mechanical properties will be included. Modeling results along with the mechanical and optical testing results have been detailed and compared with previously obtained results. Future work focuses on alternate material sets for a reduction in operational voltage, improvements in optical efficiency and technology demonstrators for verification of massively parallel I/O performance.
The eventual, widespread insertion of Micro-Opto-Electro-Mechanical Systems (MOEMS) into the marketplace rests fundamentally on the ability to produce viable components that maximize optical performance while minimizing power consumption and size. In addition, the incorporation of optical reconfigurability into custom MOEMS devices offers an extra degree of freedom not possible with conventional components. Active control of surface topology allows for one component to perform multiple functions thus reducing cost and complexity. This paper will focus on the current status of the MOEMS research program at the University at Albany Institute for Materials’ (UAIM) NanoFab 200 with several examples described to illustrate component and system development. In particular, among the MOEMS research portfolio at UAIM, the development of selected MOEMS-based, active optics will be discussed. This active control of diffraction and reflection forms the basis for the utility of such devices.
Leveraging the extensive research expertise on the patented MEMS Compound Grating (MCG), emphasis will be placed on the extension of the approach to novel designs, materials and fabrication methods to yield low power, high performance prototypes. The main focus of this paper is on the development of a polymer version (including sacrificial layer, in some designs) of the MCG which allows for ease of fabrication and a reduced electrostatic actuation voltage. Following a system design effort, several generations of the component were fabricated to optimize the process flow. Component metrology, electromechanical characterization and initial results of optical tests will be reported. A second example presented is the design and prototype fabrication of a spring micrograting using a customized SOI process. This highly flexible component builds on the MCG concept and yields an order of magnitude reduction in actuation voltage. These examples will be presented against a backdrop of the broad UAIM program to provide an overview of the applications of MOEMS and their integration with complementary technologies at the wafer level.
We are investigating the development of a rapid and highly sensitive detection method for immunoreactive substances combining MEMS (Micro Electro Mechanical Systems) technology and the appropriate immune stimulant or response factors. Cantilevers of micrometer scale can be used for trace detection of mass change. When a layer of an antigenic substance is covalently deposited, the cantilever is capable of capturing antibodies from samples with high affinity and specificity. The antigen/antibody binding causes multiple physical changes in the cantilever device, including a shift of effective mass and a change in surface tension. The change of effective mass consequently induces a shift in the cantilever’s natural resonant frequency. By monitoring these changes with an optical readout mechanism, the presence of immunoreactive targets in the sample can be detected. This detection method can be used for various types of targets with immunoreactivity and therefore is potentially applicable in hazardous substance monitoring and disease diagnosis. In our effort, phoS1, an antigen shed by Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), is utilized for rapid and economic TB detection.
This paper focuses on the development of a custom MEMS-based array which will facilitate cell secretion studies by enabling parallel electrochemical detection of secretion events from separate cells with millisecond resolution. Initial prototypes of the microarrays have been fabricated with well-shaped gold electrodes which roughly conform to the shape of a single cell. Amperometric measurements on bovine adrenal chromaffin cells using the prototype microarrays concluded that 80% of the catecholamine secreted from the cells was captured by the well-electrodes. This was a 4-fold increase in detection efficiency over the conventional carbon fiber electrode method. To expand the applicability of this method, additional cell-lines and microarray designs are under investigation. An amphibian fibroblast cell-line (FT cell-line, American Tissue Culture Collection) is being used in our lab. FT cells can take up hormones or other biological compounds from the culture media through a non-specific uptake mechanism which is still under investigation. Microarrays of a new design have been fabricated with patterned gold electrodes on polyimide. A different testing method will be applied to these new microarrays. The FT cells will be cultured directly on top of the microarrays to cover the gold electrodes. Cells will then be loaded with norepinephrine by incubation in media containing 1mM norepinephrine. Rapid elevation of intracellular Ca2+ levels triggers the exocytosis of norepinephrine which then can be detected by the gold electrode. The new polyimide based microarrays have been successfully used to support confluent growth of the FT cells. Loading of the FT cells with norepinephrine and electrochemical detection tests are underway.
KEYWORDS: Semiconducting wafers, Wafer bonding, Interfaces, Silicon, Microelectromechanical systems, Temperature metrology, Reliability, System on a chip, Polymers, Scanning electron microscopy
Wafer bonding has attracted significant attention in applications that require integration of Micro-Electro-Mechanical Systems (MEMS) with Integrated Circuits (IC). The integration of monolithic MEMS and electronic devices is difficult because of issues such as material compatibility, process compliance and thermal budget. It is important to establish a wafer bonding process which provides long-term protection for the MEMS devices yet does not affect their performance. The attentions for such integration are at the die level and wafer level. Recently, the trend is toward wafer-level integration as a cost effective solution to combine sensing, logic, actuation and communications on a single platform. This paper describes the development of low temperature bonding techniques for post-CMOS MEMS integration in system-on-chip (SOC) applications. The bonding methods discussed in this paper involve Benzocyclobutene polymer (BCB) as glue layer to joint two 200 mm wafers together. The bonding temperature is lower than 400°C. Four-point bending and stud-pull methods were used to investigate the mechanical properties of the bonding interfaces. These methods can provide critical information such as adhesion energy and bonding strength of the bonded interfaces. Initial test results at room temperature showed that the BCB bond stayed intact up to an average stress of 50 MPa. It was observed that the BCB bond strength decreased with increasing temperatures and the energy release rate decreased with decreasing BCB thickness.
A new focused ion beam (FIB) miore method is proposed to measure the in-plane deformation of object in a micrometer scale. The FIB moire is generated by the interference bewteen a prepared specimen grating and FIB raster scan lines. The principle of the FIB moire is described. Several specimen gratings with 0.14 and 0.20 micron spacing are used to generate FIB miore patterns. The FIB moire method is successfully used to measure the residual deformation in a MEMS structure after removing the SiO2 sacrificial layer with a 5000 lines/mm grating. The results demonstrate the feasibility of this method.
Despite the recent sag in the optical telecom sector, the development and application of Micro-Opto-Electro-Mechanical Systems (MOEMS)-based devices for optical interconnects continues to expand. The utility of such fundamental research is finding increasing relevance in a variety of technical and commercial areas. This paper will report on the present status of the diffractive and reflective components and arrays that are being developed at the University at Albany’s Institute for Materials (UAIM) NanoFab 200. Selected examples include the current generation of the patented MEMS Compound Grating (MCG) and an innovative micro-scanner device, both of which are being examined for inclusion in prototype interconnect systems.
These devices are based on a dual technology development path which includes decreasing feature size and increasing integration level. The MCG prototypes are currently produced with 1-2 micron feature size in 144 element arrays. The surface topology of these components can be controlled using electrostatic attraction to yield both angular deflection and wavelength separation. The optical and mechanical performance of these devices that use either polysilicon or silicon dioxide as a structural material will be reported. Several prototype MCG array architectures have been interfaced with optical sources including VCSEL arrays to test optical interconnect concepts. In addition, recent work on an innovative micro-scanner will be discussed. The micro-scanner is based on a cantilever design with access electrodes to electrostatically control deflection in multiple planes. Details of the components including simulation, fabrication and initial prototype performance tests will be presented.
We are focusing on the development of a biochip which will enable massively parallel amperometric measurements on single cells for exocytosis studies. Initial prototypes have been fabricated with picoliter-sized wells which roughly conform to the shape of the cells. The electrochemical measurement using the prototype devices can capture a large fraction, approximately 80%, of the catecholamine release with millisecond temporal resolution. With this prototype device, cells must be manually positioned into the micro-wells by a micromanipulator. Therefore, two new designs incorporating three dimensional microfluidic structures have been developed for automatic cell positioning. One design is based on thin silicon diaphragms with picoliter-sized well arrays, while another has 1μm silicon nitride membranes. Both designs have through-membrane holes and are designed in such a way that the cells will be automatically positioned onto electrodes once a suitable pressure differential is applied between the two sides of the thin diaphragms. Details of the microfabrication process for both designs will be presented in this paper as well as results of automatic cell positioning tests.
In this paper, modeling and simulation of a novel micro-centrifuge for biomedical and biochemical applications is described. The micro-centrifuge that we designed can work not only as a shaker but also as a detector of cell growth, which has great potential applications in bioanalysis. The initial design contains four channels for mixing or collecting of samples by centrifugal force. The rotor, the key component of this device, is actuated using electrostatic force. There are four electrodes on the substrate to actuate the micro-centrifuge rotation around the X-axis (lateral in plane) and the Y-axis (vertical in plane) respectively, and eight pairs of comb drives are used to actuate the micro-centrifuge rotation around the Z-axis (perpendicular to the XY plane). The multiple axis actuation design makes it very flexible to control the micro-centrifuge. Because of its small feature size, the cost of the reagent used for the micro-centrifuge will be greatly reduced. An array of micro-centrifuges will be designed to achieve a fast cycling time. A Finite Element Analysis (FEA) has been completed to analyze the static and dynamic performance of the micro-centrifuge, such as the natural frequencies, tilt angle, and driving voltage. A novel fabrication process using SOI technology has been proposed which is now being developed.
There has been a growing interest in the research of microfluidic management systems, e.g., for DNA sequencing devices, biological cell manipulation systems, chemical analysis systems and microdosage systems. microfluidic management is crucial capability in most biomedical nanodevices and micro fuel cells using methanol as fuel. It involves the manipulation of fluids ranging from a scale of nano to millimeters. Basic building components for a microfluidic management system are microvalves and micropump s together with the interconnect fluidic channels . Micropumps can have passive and/or active valve. Because of the increasing functionality in portable electronic devices and systems, the micropumps and mic rovalves should be compact, reliable, long-lifetime and high energy efficient. In this report, the design, fabrication and modeling of a low power, low voltage, leak proof microfluidic management systems will be discussed.
Optical ADD/DROP multiplexers (OADM) are incorporated into all-optical network structures that provide fixed access to a subset of the wavelengths in Wavelength Division Multiplexer (WDM) systems. The rapid growth of broadband data communications and the drive toward cost reduction have made optical MEMS (Micro- Electro-Mechanical Systems) an extremely attractive technology for applications in optical communications. This paper will present theoretical analysis, simulation and testing results of an ADD/DROP multiplexer based on the MEMS-based micro-actuators. The micro-actuator is a MEMS-based compound grating (MCG) with a reconfigurable surface that couples the mechanical motion with optical diffraction. The diffraction patterns depend on the wavelength, incident angle and the grating structural parameters. This property is used to design an OADM that can be applied to broad areas in optical communication. A theoretical analysis is presented to establish the relationship between diffraction beams and the structural parameters of the grating, the wavelength of incident light, incident angle. Prototypes of these micro-actuators have been fabricated. The initial testing demonstrated the feasibility of using the MCG as an OADM. New designs of the MCG for application to the 1.55um optical telecommunication standard will be discussed.
We are developing a novel readout for secretion of hormones and neurotransmitter on micro/nanofabricated chips. Traditional biochemical assays of signaling molecules secreted from cells are slow, cumbersome and have at best, a temporal resolution of several seconds. On the other hand, electrochemical measurement of hormone or transmitter secretion can obtain millisecond temporal resolution if the diffusion distance between the release site on the cell and the working electrode is within 1 micron. Carbon fiber microelectrodes can have millisecond time resolution, but can only measure release form a small fraction of the cell surface. We have fabricated arrays of Au electrodes in wells micromachined on the surface of silicon microchips. Each well/microelectrode roughly conforms to the shape of a single cell in order to capture release forma large fraction of the surface area of each cell with minimal diffusional delays. This paper will present details of the microfabrication process flow as well a initial results demonstrating millisecond-resolution measurement of catecholamine secretion form adrenal chromaffin cells. Our goal for this project is to develop enabling technology for massively parallel systems on a chip such as cell-based biosensors to detect neurotoxins and high-throughput assays of drugs that affect neurotransmitter release.
The use of Micro-Electro-Mechanical Systems (MEMS) technology has opened the door for many applications. In particular, by exploiting the reconfigurability of optical surfaces fabricated with this technology, many sensor, communication and spectroscopic systems can benefit. The controlled re-direction of single or multiple optical input sources can lend itself to high throughput sample analysis or massively parallel optical connectivity. In addition, the change in a MEMS-based optical surface can result in a flexible spectral analysis of incoming radiation. We report on the recent advances in our projects which are focused on the design/simulation, materials processing and integration issues involved with the creation and optimized operation of such diffractive micro-arrays. In this presentation, the state of the art in such devices will be presented which will include the process flow associated with production, structural metrology, optical performance, and parallel switching capabilities of the systems. The use of numerous materials including polysilicon, silicon dioxide and selected polymers as structural layers has enabled the production of devices which can be tailored for specific, performance related applications. Examples to be presented include diffractive surfaces with substantial (1 cm x 1 cm) active areas as well as large arrays with sub-micron feature sizes. Functional integration of the prototype devices include optical interconnects, active spectroscopy and bio/chem diagnostic systems.
Two-dimensional (2D) scanners can be used for displays, printers, optical data storage devices, optical scanning microscopes, and free-space optical interconnects. In this paper, we will describe the modeling and simulation of a novel cantilever microscanner. The scanner is actuated using electrostatic force. The cantilever beam connects to the top electrode. The bottom four electrodes on the substrate provide extra feedback for the control of the cantilever beam. A thorough mechanical analysis (both static and dynamic) using Finite Element Analysis has been performed. Key design parameters such as driving voltage, tilt angle and resonant frequencies have been investigated. The model has not been verified by experimental data but a fabrication process flow has been designed. The fabrication of this novel cantilever microscanner is in progress.
Interconnect bottleneck in emerging integrated circuitry (IC) has generated a need for alternative signal transmission solutions, such as optical technologies, in chip-level applications. The present paper discusses target parameters for chip-level optical interconnects (CLOIs) that yield superior performance starting with the 70 nm IC node, and possibly extending down to the 25-15 nm node. The benefits and disadvantages of various CLOI system and component solutions are reviewed. In particular, this paper discusses critical fundamental and technological challenges that need resolution to enable massively parallel CLOI links with a total throughput of 10-25 Tb/s, reduced power consumption in comparison with electrical wires, and enhanced density. Recent results from the presenting authors are summarized with an emphasis on CLOI specific solutions. These results include the development of InAs quantum dot gain medium to increase the operating temperature of laser arrays above that of Si ICs. Controllable routing of VCSEL- emitted beams is carried out through a microsystem-based reconfigurable free-space interconnect system which employs optical diffractive or reflective structures. This work also explores a novel hybrid integration protocol that allows self-aligned bonding of massive arrays of III-V components to Si electronics, and ensures low thermal budget and reduced stress.
Following over a decade of MOEMS component development, attention in the research, development and commercial arenas has begun a significant shift to system-level integration of these structures. Applications abound in fields including optical communications, integrated sensors and bio/chemo diagnostics. Furthermore, the impending need for wafer- level integration of MOEMS with logic and actuation is driving R&D into developing a compatible process flow for ultimate, low-cost technology deployment. This paper will describe recent advances in MOEMS development and integration projects at the UAlbany Institute for Materials (UAIM). This discussion will focus on operational details of selected MOEMS projects including diffractive/reflective arrays, VCSEL arrays, and integrated sensor systems. These research and development details will be presented against a backdrop of the NanoFab 200 at UAIM, a unique 200 mm wafer prototyping and integration facility. In particular, reconfigurable diffractive and reflective arrays are currently under development in several complementary programs at UAIM. These programs encompass optical interconnect studies, active spectroscopy and metrology development. This paper will present the current status of these programs that are focused on optical performance improvements, process flow integration, packaging and lifetime tests. To complement these activities, selected MOEMS components are being integrated with VCSEL arrays for application to a variety of sensor systems. Development details of the VCSEL arrays and compatibility issues with custom MOEMS systems will be described. Finally, selected details of 200mm wafer-level integration studies will be presented to illustrate challenges and opportunities.
We present measurements of the nanoscale elastic properties of hinge structures supporting micro-mirror arrays using a new characterization technique called Ultrasonic Force Microscopy (UFM). This technique is based on Atomic Force Microscopy with ultrasonic excitation which provides a means of testing the elastic response at MHz frequencies. The simultaneous recording of topography with elastic imaging allows the elimination of any artifacts. In this report, we demonstrate that UFM can achieve nano-scale elastic resolution to reveal mechanical stress induced changes as well as process induced material fatigue in the micro-mirror devices. The main aim of this study is polysilicon-based hinge structures that support the micro-mirror because they show the highest stress during mirror switching. Our results indicate that no significant structural and mechanical change of the polysilicon-based hinge support structure occurs even after more than 1,000,000,000 switching cycles. This method offers a non-destructive way to perform reliability characterization on MEMS devices. This technique developed will offer new opportunities for the evaluation of structural and mechanical integrity of MEMS devices.
The MEMS-based Micrograting (MCG) is a basic building component in many optical systems. This paper presents the fabrication technique of a custom MCG whose optical surface can be reconfigured electrostatically. The ruling is made of SiO2 and both the top and the bottom electrodes are made of Cr/Au. A robust three-mask process was designed and developed. The reduced ruling width (1 micrometers ) is not a simple miniaturization of previously reported 3 micrometers and 4 micrometers ruled microgratings. Because of mechanical integrity and fringe effects at the ruling edge during device operation, the design and fabrication of the new 1 micrometers ruled MCG require new material and process integration. To achieve self-alignment between the top electrode and the ruling, the top electrode is patterned first then the pattern is transferred to the ruling material by Reactive Ion Etch (RIE). Experiments show that the lift-off process results in a smoother top electrode than ion milling. Residual stress proves to be an important factor that influences the device performance. Because Ni is used as a hard mask for RIE, the resulting stress gradient causes the rulings to bend up. The actuation voltage is increased as a result of this increased air gap. Annealing experiments are performed to reduce the material residual stress and lower the pull-in voltage. Auger Electron Spectroscopy (AES) data shows that the adhesion layer (Cr) diffuses through the Au and gets oxidized when annealing temperature is higher than 450 degree(s)C. It was found that the optimum annealing condition is at 350 degree(s)C for 1 hour. Finally, optical tests these prototypes show that the diffraction patterns switch at about 11 V, much lower than the devices reported previously.
KEYWORDS: Imaging systems, Digital imaging, Cameras, Signal detection, Luminescence, Acquisition tracking and pointing, Optical testing, CMOS sensors, Sensors, Analytical research
Tuberculosis (TB) remains the leading cause of death in the world from a single infectious disease, and the threat is becoming more critical with the spread of multi-drug resistant Tuberculosis (MDR-TB). TB detection, and susceptibility testing for drug resistant strain identification, is advancing with the development of Luciferase Reporter Mycobacteriophages (LRM). LRM will emit visible light at very low intensity when in the presence of live mycobacteria cells such as Tuberculosis strains. InterScience, Inc., together with its collaboration, is developing a highly sensitive, real-time digital detection system for the analysis of luminescent assays. Recent advances in system sensitivity, design, and implementation, as well as preliminary results of the development of individual test cartridges, will be presented. The ultimate goal of this work is to provide a versatile luminescence detection tool for widespread research and clinical applications.
The rapid advancement of electro-optical components and micro-mechanical devices has led to increased functionality in decreasing package sizes. In particular, the development of massively parallel arrays of optical sources such as Vertical Cavity Surface Emitting Lasers (VCSEL) and innovative micro-opto-electro-mechanical systems (MOEMS) has opened the door for new possibilities. Recently, there has been a drive toward integration of the sensing, processing and actuation functions in a single package for fully integrated performance. One area which can benefit from this research is real time, spectroscopic analysis of biological and chemical samples. Numerous situations require a compact, self-contained bio/chemometric system for rapid, low cost spectral analysis or monitoring. To fully realize this potential, further component development and integration issues must be addressed. This paper will present the status of the VCSEL and MOEMS programs at the Institute and initial integration activities. The VCSELs are based on multiple quantum well Ga/As/InGaAs and GaAs/AlGaAs architectures with monolithic, epitaxially grown distributed Bragg reflectors. The VCSEL arrays have 6-15 micron apertures, 100 micron pitch and a mA threshold current. In parallel, the MOEMS program is focused on the development of active, reconfigurable diffractive and reflective arrays whose surface topology can be changed in real time. These MOEMS arrays can be sued to redirect light for flexible interrogation of samples. The combination of these two technologies offers a unique opportunity for fully functional systems on a chip.
MEMS promise to revolutionize nearly every product category by bringing together silicon-based microelectronics fabrication with silicon micromachining technology, thereby, making possible the realizing of complete systems-on-a-chip.
The evolution of computer chip technology has been marked by a steady progression toward higher performance which will soon be limited by the time delay associated with interconnects. This has led to consideration of alternate interconnect methods to complement or replace conventional metal/dielectric architectures for both intra-chip and chip to chip and detectors. The interconnect medium for this approach, however, is still under conceptual design and has spawned many candidates. Various configurations of static micro-optic arrays however, recent consideration has been given to active, reconfigurable optics based on micro-electro-mechanical systems (MEMS) technologies. These Optical MEMS or MOEMS have enabled innovative devices which can control phase, amplitude and direction of input light beams. One area which has recently received much attention is the creation and use of both reflective and diffractive arrays. This paper will present the development and use of active, reconfigurable MOEMS prototypes applied to proof of principle optical interconnect systems. We have been studying several array architectures consisting of gratings, columnar reflectors and micromirrors. For example, the patented MEMS-based compound grating (MCG) is currently being developed to enable a new class of diffractive arrays which can be used as a massively parallel switch. The MCG is a device which is a superposition of two or more diffraction gratings whose surface topology can be controlled. Various prototype arrays of these MCG devices have been designed, modeled, fabricated and tested. Initial result of these studies will be presented. In addition, application of the digital micromirror device to this problem will also be discussed. Using a custom control software and optical setup, preliminary results from the integration of a DMD into an optical interconnect test stand will be presented.
Tuberculosis (TB) remains the leading cause of death in the world from a single infectious disease and the threat is becoming more critical with the emergence and spread of multi-drug resistant tuberculosis (MDR-TB). Existing methods for detection of various strains of mycobacterium tuberculosis are complex, time consuming and expensive, and therefore, not suitable for use in developing countries where the spread of the disease is most rampant. Currently, a digital detection system based on advanced digital imaging technology, including CMOS and image intensification technology, is being developed by InterScience, Inc. for use with the luciferase reporter mycobacteriophages technique as developed at the Albert Einstein College of Medicine. This compact, low cost and high sensitivity system for rapid diagnosis and drug susceptibility testing for TB will have an immediate impact for both research and clinical applications. It is envisioned that the instrument will be suitable for use as a portable tool for rapid screening of MDR-TB in both developed and developing countries. The development of the system, recent results and a comparison to competing technologies will be presented.
The control of optical wavefronts can be accomplished in many ways and a wide array of static optical components have been developed to address this task. However, for many applications, the use of static optics limits the usefulness of the system. With the recent development of advanced micromachining methods, a new degree of flexibility has been introduced. The application of Micro-Electro-Mechanical Systems (MEMS) technologies to the field of optics has opened new doors for reconfigurable surfaces which can control the reflection, transmission or diffraction of light. This paper will present one such class of devices based on the patented MEMS Compound Grating (MCG) in which a mechanical structure is created that can alter the diffractive behavior of the device through the active reconfigurration of the surface. The rulings of the MCG consist of doubly constrained beams with a custom electrode structure for controlled electrostatic adjustment. Using this ability to actively influence the diffraction of incoming light, increased information can be extracted without the addition of extra optical components. For example, this unique feature can resolve the order- wavelength uncertainty in as spectral instrument thus removing the limitation of free spectral range typical of spectrometers based on conventional diffraction gratings. This ability has implications for a wide variety of optically based sensor systems. The current status of the MCG development will be presented including materials and performance issues and initial integration into both commercial and custom, prototype spectrometers.
In most advanced imaging systems designed for low light level applications, the heart of the detection process is an image intensifier. While such imaging systems are ideal in low light, they are sensitive to sudden increases in brightness levels within the field of view. These sudden bright spots are caused by a variety of sources (both intentional and not) and can result in a loss of contrast, blinding of the imaging system and damage to the components. As a safety measure against this situation, most systems incorporate global methods for automatic protection against bright sources. Unfortunately, this results in loss of gain and image contrast over the entire field of view, even if the bright source occupies only a small portion of the image. Exposure control over individual segments of the image is required. We present initial results from a unique implementation of the Digital Micromirror Device (DMDTM) technology. Through proper placement of the DMD in the optical path and by providing an automatic feedback control loop from the intensified digital imager, sections of the image plane can be automatically diverted from the optical path by controlling the mirror pixels in those affected areas. An innovative approach, the DMD-based Anti-Blooming System (DABS), has been developed. Using rapid digital processing, this control can be ultimately implemented between frames of the imager to both preserve the hardware and allow for seamless return to a high contrast image. Repeated polling of the image plane through the feedback loop will allow for active control of the intensified image. A system description of the DABS and successful results from initial closed loop operation are presented.
Tunable diode lasers have become a light source of choice for spectroscopic applications because of their small size, high efficiency, reliability, and low cost. Tuning for a particular wavelength is commonly realized by using the Littman-Metcalf external cavity configuration with a diffractive grating and rotating mirror. Using this approach, mechanical moving parts and a high degree of precision in the rotation mechanism are required for wavelength selection. Because of this mechanical motion, the tuning process is relatively slow. In some spectroscopic applications sample probing at more than one wavelength is desirable, which currently requires two or more lasers. The development of a single laser source with fast selection over a definable set of wavelengths, also capable of simultaneous emission of a multi-line spectrum, is described. Such a laser can be used to match the spectral signature of the sample and would dramatically increase the speed and reliability of a laser spectrometer. The design is based on an external-cavity configuration with fast computer controlled (in the millisecond range) line selection and has no moving parts. The laser is capable of emitting sets of multi-line near infrared spectra, each spectrum stored as a record in a computer database and matching the spectral signature of a particular chemical component, thus facilitating rapid and reliable spectroscopic detection and analysis of compound samples. The laser design and experimental test results are presented and discussed in the paper.
The advent of micromachining has opened new doors for reducing the size and weight of conventional systems. A significant example is in the area of optics in which the size reduction can be exploited to produce ultra-miniature systems using MEMS device as the sensing or control elements. Using MEMS-based fabrication methods (the MUMPS runs), a series of optical diffraction gratings has been produced to examine limitations on the production methods and explore alternative applications. These devices consist of a variety of structures including single gratings, arrays of gratings and multi-periodic gratings. These devices are based on 3D architectures which can be adjusted in real time using electrostatic attraction from custom segmented electrode structures. The gratings were released and packaged for laboratory tests. Selected packaged devices were equipped with windows and integrated into a compact spectrograph to document spectral quality and performance. Preliminary results of mechanical, optical and electrical tests will be discussed.
The use of bio-chemiluminescence immunoassay (BL/CLI) technology for molecular and cellular characterization is rapidly evolving. The excellent selectivity of this method can be exploited to identify the presence and distribution of specific cells. Current work involves the advancement of the required methods and technologies for application to the analysis of vascular wall surfaces. In this effort, various enzyme-linked antibodies are being explored which can be directed to cell surface antigens producing a luminogenic reaction. To aid in the analysis of this light emission, a custom high resolution digital imaging system which couples a multi-megapixel CCD with a specially designed image intensifier is under development. This intensifier system has high spatial resolution and excellent sensitivity in the wavelength region of the candidate BL/CL emissions. The application of this imaging system to BL/CLI requires unique performance characteristics and specialized optical design. Component level electro-optical tests of the imaging system will be presented along with design considerations for an eventual catheter based instrument. Initial in vitro experiments focused on the performance limits of the optical system in discriminating candidate luminogenic reactions. The main objective of these tests is the identification of suitable enzyme catalyzed systems for ultimate application to in vivo vascular tissue and cell diagnosis.
Variations based on bone growth and development make stress and fracture propagation differ greatly in pediatric skulls as compared to adult skulls. Differentiating the stress propagation between the pediatric and adult skulls can improve diagnostic prediction when presented with direct frontal impact on a pediatric skull, a fairly common occurrence in the clinical environment. Critical diagnostic information can be learned from an in depth study of stress propagation as a function of impact force at critical locations on the periorbital region of the human skull. The Division of Pediatric Otolaryngology at Albany Medical College and InterScience, Inc. are utilizing electronic speckle pattern interferometry detection (ESPI) and high resolution imaging to evaluate and compare stress propagation in pediatric and adult skulls. A dual detection ESPI system was developed which integrates a medium resolution (2/3') CCD capable of real-time image processing, with a high resolution, megapixel detector capable of limited real time acquisition and image processing in software. Options to allow for high speed detection include integrating a custom, high performance image intensifier with the megapixel detector leg to be used as a high speed gate. The dual optical layout will allow for continuous and pulsed ESPI evaluation of calibrated impacts at specific landmarks on the skull. The goal of this work is to produce a full quantitative analysis of the stress propagation in pediatric versus adult skulls for a better understanding of bone dynamics. The work presented below concentrates on the development of the dual detection ESPI system and initial results achieved with an adult cadaver skull.
KEYWORDS: Video, Field programmable gate arrays, Cameras, Video processing, Real time video processing, Interferometry, Video compression, Image quality, Surgery, Data compression
The use of an off-the-shelf general purpose processing system supplied by Giga Operations as applied to real-time video applications is described. The system is modular enough to be used in many scientific and industrial applications and powerful enough to maintain the throughput required for real-time video processing. This hardware and the associated programming environment has enabled InterScience to pursue research in real-time data compression, real-time Electronic Speckle Pattern Interferometry (ESPI) image processing, and industrial quality control and manufacturing. The system is based on Xilinx 4000 series field programmable gate arrays with associated static and dynamic random access memory in an architecture optimized for video processing on either the VL-Bus or PCI. This paper will focus on the design and development of a real-time frame subtractor for ESPI using this technology. Examples of the improvement in research capability provided by real-time frame subtraction are shown, including images from biomedical experiments. Further applications, based on this system are described. These include real-time data compression, quality control for production lines as part of an automated inspection system and a multi-camera security system allowing motion estimation to automatically prioritize camera selection.
Electronic Speckle Pattern Interferometry (ESPI) is a nondestructive optical evaluation technique that is capable of determining surface and subsurface integrity through the quantitative evaluation of static or vibratory motion. By utilizing state of the art developments in the areas of lasers, fiber optics and solid state detector technology, this technique has become applicable in medical research and diagnostics. Based on initial support from NIDCD and continued support from InterScience, Inc., we have been developing a range of instruments for improved diagnostic evaluation in otolaryngological applications based on the technique of ESPI. These compact fiber optic instruments are capable of making real time interferometric measurements of the target tissue. Ongoing development of image post- processing software is currently capable of extracting the desired quantitative results from the acquired interferometric images. The goal of the research is to develop a fully automated system in which the image processing and quantification will be performed in hardware in near real-time. Subsurface details of both the tympanic membrane and vocal cord dynamics could speed the diagnosis of otosclerosis, laryngeal tumors, and aid in the evaluation of surgical procedures.
One significant avenue for cost containment in medical care is the application of affordable spin-off technology. Innovative methods for the efficient prevention and treatment of atherosclerotic plaques in cardiac arteries will have significant implications for reducing health care costs in a large patient population. We report on preliminary work aimed at exploiting advanced sensing, fiber optic and materials technologies to create an innovative medical instrument: the Ultrathin Angioscopic Guidewire (UAG). The UAG uses an innovative method to combine high resolution fiber optic imaging bundles with flexible guidewire extensions into a integral unit having a diameter of less than 350 microns. The UAG would serve as the guidewire over a integral unit having a diameter of less than 350 microns. The UAG would serve as the guidewire over which the treatment catheter would ride eliminating repeated removal and reinsertion of the catheter for evaluation. The resulting images are coupled to a high resolution, image intensified detector. Use of digital image capture before and after treatment combined with frame processing allows for a quantitative evaluation of lesion removal and archival data to establish treatment efficacy. Once developed, this instrument will be particularly useful in conjunction with current interventional procedures. As a diagnostic tool, the intensifier in the UAG allows for sensitive imaging for application to in vivo bio/chemiluminescent immunoassays. We will present design details and discuss proof of principle results with the first prototype UAG.
The steady development of megapixel detector arrays with decreasing pixel size has improved the performance of present imaging systems. These high spatial resolution detectors have been incorporated into a variety of scientific experiments. The sensitivity of the diode arrays has allowed significant progress in instrumentation development and application. However, full application of these detectors to low light level measurements has been hampered by the lack of image intensifiers which can fully exploit the available spatial resolution of the diode arrays. Current architecture of image intensifiers allows significant room for improvement. We involved in a project to design, develop and characterize an 18 mm GEN II image intensifier with improved spatial resolution. Recent advances in microchannel plate production and fiber optic architecture have been exploited to produce a series of image intensifiers. A production run of a series of tubes with reduced cathode to MCP spacing, reduced microchannel diameter and pitch, reduced MCP to phosphor screen spacing and an integral fiber optic taper has been carried out. This intensifier output will be visually examined and coupled to a megapixel array for digital characterization. The goal is to produce a significantly higher limiting spatial resolution to allow for improved measurements in scientific, commercial and military applications. First results from this production run will be discussed and compared to physical performance models.
Optical fibers have long been used for visual inspection inside the human body for medical diagnoses and treatment. By making use of sophisticated optical interferometric and ultra- small imaging techniques, combined with automated image processing, it is possible to extract significantly increased information for more accurate medical diagnoses. With support from NIH under the SBIR program, we have been developing a range of such instruments. One of these supported by the NIDCD is capable of providing detailed spatial information on the vibratory response of the tympanic membrane (TM). This instrument involves the examination of the TM by means of high speed electronic speckle pattern interferometry (ESPI). This provides a real time view of the vibration patterns of the TM for clinical diagnosis. This Interferometric Otoscope consists of mode conserving fiber optics, miniature diode lasers and high speed solid state detector arrays. We present the current status of the research including holography and ESPI of TM models and excised temporal bone preparations. A second instrument, also developed with support from NIDCD, is for application to the larynx. This system is also ESPI based but will incorporate features for direct vocal cord (VC) examination. By careful examination of the vibratory response of the VC during phonation, the characteristics of the mucosal wave may be examined. Adynamic regions of the cords can signal the start of lesions or cysts. Results of surgery can be evaluated in a quantitative manner. The design of a clinical prototype and preliminary electro-optic experiments on excised larynges and VC models will be presented.
Current medical instrumentation research at InterScience, Inc. is aimed at utilizing state of the art electro-optics in the development of a diagnostic fiber optic instrument capable of quantifying vibration patterns in real time. This work is in collaboration with the Division of Otolaryngology of the Albany Medical College. The innovative diagnostic probe system design involves the miniaturization of an electronic speckle pattern interferometry (ESPI) system through the use of fiber optic elements coupled with high speed image acquisition from a solid state matrix detector. Subsequent frame by frame processing produces a high quality three-dimensional spatial representation of the vibrational pattern. The diagnostic probe system is being developed for quantitative tympanic membrane and vocal cord vibration analysis. The significance of the introduction of this instrument to the medical community is the contribution it could make in the efficiency and effectiveness of the diagnosis of otolaryngological disorders. Specific applications include the evaluation of tympanosclerosis, stiffness related middle ear disorders, ossicular chain abnormalities, tympanic membrane replacement, vocal dysphonias, and early detection of laryngeal carcinomas, cysts, and phenomenological properties of mucosal wave dynamics. The current instrumentation research is focused on the production of a prototype system for clinical trials. This research is based in ESPI optical system development and miniaturization, system hardware and software development, and clinical design of the probe heads within anatomical limitations. Significant advantages of this diagnostic tool over currently used instrumentation and procedures are the real time capabilities of the instrument, the ability to quantify the vibrational pattern in time and space, and the possibility of establishing a database of patient history and disorder characteristics. Once fully developed and integrated into the clinical environment, this system will have a profound effect on the diagnostic capabilities of the otolaryngologist and other clinicians and researchers of communication sciences and disorders.
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