Dr. Daniel Garcia Profile

Dr. Daniel Garcia

at Univ of California Los Angeles

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Publications (2)

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Proceedings Article | 21 August 2009 Paper

A parametric design study of an electrochemical sensor

Daniel Garcia, Ting-Hsuan Chen, Fang Wei, Chih-Ming Ho

Proceedings Volume 7397, 73970R (2009) https://doi.org/10.1117/12.825902

KEYWORDS: Electrodes, Sensors, Molecules, Interference (communication), Biosensors, Photoresist materials, Signal to noise ratio, Sensor performance, Target detection, Semiconducting wafers

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Biological systems contain a multitude of molecules with specific functions and three-dimensional shapes that enable them to selectively interact with other molecules in a coordinated fashion. Engineering, on the other hand, has produced devices that operate on the micron-scale and that combine electronic and mechanical systems. Microelectromechanical Systems (MEMS) offer advantages such as the integration of a variety of functions into a single device (i.e. "lab-on-a-chip" platforms) and portability for "point-of-care" diagnostics. This study utilizes a microscale electrochemical sensor for detecting BoNT apatamer hybridization, in which we first used top-down lithographic processing to define the pattern of the electrodes and then used bottom-up manufacturing to modify the surface molecular properties for reducing non-specific binding. The goal was to systemically examine the effects of the design parameters of an electrochemical DNA sensor. Four key design parameters were examined: the area of the working electrode, the area of the counter electrode, the separation distance between the working and counter electrodes, and the overlap length between the working and counter electrodes. Through a log-log analysis of the current generated, representing the signal or noise, across variations of the different parameters, the significance of each parameter in sensor performance was determined. We found that the area of the working electrode was important in the performance optimization of the sensor, while the performance seemed to be independent of the other three parameters. The output signal level increased with the area of the working electrode and the signal-to-noise ratio was about constant in the tested range.

Proceedings Article | 10 September 2007 Paper

Spatial redistribution of nano-particles using electrokinetic micro-focuser

Daniel Garcia, Aleidy Silva, Chih-Ming Ho

Proceedings Volume 6648, 66480V (2007) https://doi.org/10.1117/12.735440

KEYWORDS: Dielectrophoresis, Particles, Electrodes, Nanoparticles, Molecules, Nanolithography, Photoresist materials, Manufacturing, Control systems, Molecular self-assembly

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Current microfabrication technologies rely on top-down, photolithographic techniques that are ultimately limited by the wavelength of light. While systems for nanofabrication do exist, they frequently suffer from high costs and slow processing times, creating a need for a new manufacturing paradigm. The combination of top-down and bottom-up fabrication approaches in device construction creates a new paradigm in micro- and nano-manufacturing. The pre-requisite for the realization of the manufacturing paradigm relies on the manipulation of molecules in a deterministic and controlled manner. The use of AC electrokinetic forces, such as dielectrophoresis (DEP) and AC electroosmosis, is a promising technology for manipulating nano-sized particle in a parallel fashion. A three-electrode micro-focusing system was designed to expoit this forces in order to control the spatial distribution of nano-particles in different frequency ranges. Thus far, we have demonstrated the ability to concentrate 40 nm and 300 nm diameter particles using a 50 μm diameter focusing system. AC electroosmotic motion of the nano-particles was observed while using low frequencies (in a range of 30 Hz - 1 KHz). By using different frequencies and changing the ground location, we have manipulated the nano-particles into circular band structures with different width, and focused the nanoparticles into circular spots with different diameters. Currently, we are in the progress of optimizing the operation parameters (e.g. frequency and AC voltages) by using the technique of particle image velocimetry (PIV). In the future, design of different electrode geometries and the numerical simulation of electric field distribution will be carried out to manipulate the nano-particles into a variety of geometries.

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