Power consumption is a critical concern of many sensors used in diversified applications, especially where the replacement of batteries is impossible or inconvenient. Strain energy harvesting technique is an attractive approach to solve this problem using piezoelectric materials. The feasibility of a self-powered piezoelectric microaccelerometer system using lead zirconate titanate (PZT) thin film is studied in this paper. Since the electromechanical coefficient d33 of PZT is larger than d31, and the transverse (33 mode) mode is also easier to fabricate, our design and analysis are focused on the transverse mode in constructing the PZT-based self-powered microsystem. The PZT-based cantilever structure with interdigitated electrodes and silicon seismic mass at the free end are designed to have specific resonance frequencies ranging from tens to thousands of hertz. The capability of energy storage and acceleration sensitivity in the proposed microaccelerometer are concurrently evaluated. A trade-off exists between these two major functions and the desirable operating frequency of the proposed system, i.e., the compromise depends on the demands of particular applications.
Ionic Conducting Polymer Film (ICPF) micro grippers with multi-finger configurations were developed using spin-on Nafion and photolithographic technology. A commercial solution from Dupont Co. (Nafion SE-5012) was used to prepare ~0.2 μm thick ionic conducting polymer film. Micro cantilever structures were fabricated which composed of Au/Nafion/Au film layers. Grippers with 2-finger and 4-finger configurations were successfully developed. We have
proved that the 2-fingered grippers can be actuated in water at ~5V DC voltages. The smallest 4-fingered grippers fabricated were 30 μm wide, 300 μm long and 0.4 μm thick for each finger. In addition, another interesting actuation behavior of the micro actuator was observed during fabrication. The actuators would curl up whenever they came in contact with water during the sacrificial release process. The curling process reversed instantaneously when the
actuators are immersed in acid. We suggest that this phenomenon is probably due to the different volume expansions of Nafion in different medium. Besides, the current-voltage property was measured. We are further studying the consistency of their behaviors to modify the design and fabrication process for potential use in biological manipulations.
The development of a novel Ionic Conductive Polymer Film (ICPF) micro actuator is presented in this paper. A commercial solution from Dupont Co. (Nafion SE-5012) was used to prepare ~0.2μm thick ionic conductive polymer film. Cantilever structures composed of Au/Nafion/Au film layers were microfabricated on silicon substrate based on photolithographic technique. The structure was released by etching sacrificial aluminum in phosphoric acid at room temperature. The smallest actuators fabricated were 200μm wide, 400μm long and 0.2μm thick. We have proved that these actuators could be fully actuated in water at ~3V DC voltages. In addition, another interesting actuation behavior of the micro actuator was observed during fabrication. The actuators tended to curl whenever contacted with water during sacrificial release process. The process reversed instantaneously with the immersion in acid. We suggest that this phenomenon is due to the different volume expansion of Nafion in different medium. We are currently studying the consistency of the actuation behaviors. In the future, the design of the structures will be modified to realize precise control of actuation behavior and practical applications.
The ability to manipulation of biological cells while having reflective-force information from the cells is a key technology necessary for many new applications in Bio-MEMS, but is currently lacking in all cellular manipulators. We will report on our preliminary experimental work in using an Ionic Conducting Polymer Film (ICPF) to develop a biological cell robotic gripper with force sensing capability. ICPF actuators are able to give large deflection with small input voltage (~5V), and also able to give relatively large output voltage due to deflection by a mechanical forces, thus are investigated as a possible material to make force-feedback controlled cellular manipulators in our work. A laser micromachining process is introduced to fabricate arrays of ICPF griping devices, which can be potentially integrated onto a substrate to develop a micro manipulation system. Individual multi-finger grippers with dimensions of 200micrometers x 200micrometers x 3000micrometers for each finger were realized. We will report on the design, fabrication procedures, and operating performance of these micro-grippers. Further development in the reduction of size of these actuators will enable effective force-feedback control of underwater micro objects and lead to new frontiers in cellular manipulation.
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