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Accepted for poster presentation at Micro Total Analysis Systems 2003, Squaw Valley, CA, October 2003.
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Oral presentation at Transducers '03, Boston, MA, June 2003.
We have demonstrated for the first time temperature gradient gel electrophoresis (TGGE) in an integrated polycarbonate microfluidic system. The temperature gradient was controlled by sensors and heaters lithographically patterned directly on a polymer substrate. Integrating micro heaters and sensors on polymer substrates requires significantly less power and allows faster response times compared with previously demonstrated macro-scale heaters, providing for highly efficient control of the temperature gradient. The ability of this platform to perform DNA mutational analyses by TGGE using a spatial temperature gradient is demonstrated.
Poster presentation at Micro Total Analysis Systems 2002, Nara, Japan, November 2002.
A technique for lithographically patterning of extremely thin (200 Angstroms) metal films on polycarbonate substrates has been developed. This is used to fabricate integrated arrays of thin film temperature sensors and heaters in a polycarbonate microfluidic device.
Appeared in ASME Journal of Mechanical Design, vol. 124, pp 223-235.
The analysis of compliant mechanisms is often complicated due to the geometric nonlinearities which become significant with large elastic deflections. Pseudo rigid body models (PRBM) may be used to accurately and efficiently model such large elastic deflections. Previously published models have only considered end forces with no end moment or end moment acting only in the same direction as the force. In this paper, we present a model for a cantilever beam with end moment acting in the opposite direction as the end force, which may or may not cause an inflection point. Two pivot points are used, thereby increasing the model's accuracy when an inflection point exists. The Bernoulli-Euler beam equation is solved for large deflections with elliptic integrals, and the elliptic integral solutions are used to determine when an inflection point will exist. The beam tip deflections are then parameterized using a different parameterization from previous models, which renders the deflection paths easier to model with a single degree of freedom system. Optimization is used to find the pseudo rigid body model which best approximates the beam deflection and stiffness. This model, combined with those models developed for other loading conditions, may be used to efficiently analyze compliant mechansims subjected to any loading condition.
Oral presentation at The 2000 ASME Design Engineering Technical Conferences, Baltimore, MD, September 2000.
In this paper, we present an improved method of modeling compliant mechanisms, and as motivation for such models, discuss the modeling and fabrication of a compliant spatial micro-manipulator. Micro-spatial manipulators differ significantly from their traditional counterparts in the types of joints which can be used. It is not practical to make a true revolute joint in a spatial micro-manipulator. Therefore, flexural sections must be used instead of traditional joints. To analyze and control the motion of such a mechanism, it is desirable to have a simplified model of the flexural sections. This can be accomplished by modeling the response of an individual flexural section fixed at one end with loads applied to the free end. This pseudo rigid body model (PRBM) can then be applied to each of the flexural sections in a compliant manipulator. Such models have been developed for cases in which only force is applied to the free end and moment acts in the same direction as the end force. In the spatial micro-manipulator presented here, it is clear that end moments will be present in some of the compliant sections, and may act in the opposite direction as the force, possibly creating an inflection point. Therefore, we have developed a model for a flexural section with end moment acting in the opposite direction as the end force creating an inflection point.
The spatial micro-manipulator is fabricated with a 3D MEMS fabrication process using deep reactive ion etching to etch wafers which are then bonded together. The manipulator is made in a singular configuration using only two bonded wafers. After fabrication, the manipulator is moved out of the plane and away from its singular configuration. In future work, the pseudo rigid body model developed here will be used to analyze the kinematics of the spatial micro-manipulator.