Reza Ghodssi   Herbert Rabin Distinguished Professor   Director, Institute for Systems Research

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Research Small Scale Energy Conversion and Harvesting  - Power MEMS Devices based on Micro-ball Bearing Technology  - MEMS-based Gray-scale Technology Power MEMS are a class of micro-electro-mechanical systems that convert energy from one form to another. The Power MEMS group at MSAL is currently working on three different projects: micromachines supported on ball bearings, gray scale technology and energy harvesting and power generation. We have successfully designed, fabricated and characterized linear and rotary micromotors and are developing a feedback control system to be integrated with these devices to achieve better stability and higher speeds. A photodiode based control mechanism allows for real time position and velocity tracking which will also play a key role in the realization of a microgenerator. We are conducting tribological studies in order to investigate the effect of the geometry, lubricating materials and environmental conditions on the bearing characteristics. In parallel, we are developing a 2nd generation rotary micromotor designed to provide sufficient torque and speed to power a MEMS-fabricated viscous pump. Using gray scale technology we developed a number of devices, such as a 3D 2-axis optical fiber aligner, a phase Fresnel lens and a 3D substrate interconnect for a MOSFET relay, and we are working to improve the vertical resolution by employing double exposure technique. In the power generation and energy harvesting domain, we are developing energy scavenging devices using a hybrid piezo/electrostatic approach for harvesting ambient environmental energy using MEMS transducers, with the focus on system-level optimization. We are also exploring novel approaches for on-chip power supply using micro-batteries based on biological materials, such as the benign Tobacco Mosaic Virus (TMV). Chemical and Biological Sensing  - BioMEMS Devices for Patterning and Sensing Biomolecules  - III-V MEMS for Integrative Optical Microsystems The biosensing projects at MSAL are aimed at developing systems for manipulating and detecting biomolecules on the microscale. This type of systems will form the basis for future high-sensitivity medical diagnostics, biohazard detection, and environmental monitoring. One aspect of our work focuses on assembling biological components within microfabricated devices by using the polysaccharide chitosan as an interface material between the organic environment and the inorganic device surface. We have used this approach to "biofunctionalize" micromechanical and photonic sensors. The micromechanical sensors operate by measuring the physical interaction of biomolecules with microfabricated cantilevers. The photonic sensors analyze biomolecules by optical excitation and collecting the emitted light. The other aspect of our work is to use III-V materials for devices with advanced optical functionality. One example of this approach is a microcantilever sensor with integrated readout based on variable optical coupling. Another demonstration is a tunable optical filter which could be used for demultiplexing or spectrometry. The major advantage of the III-V materials is that they allow for the integration of active optical components, leading toward systems on a chip. We are also working on a feedback control circuit to drive and read out the microcantilever sensors in a compact and automated manner. Efforts to deposit chitosan on III-V devices are currently ongoing to confer them with selectivity and enable highly sensitive detection of relevant biological events. Previous Projects  - Characterization of MEMS at Cryogenic Temperatures Using Focused Ion Beam  - Development of Micronozzles for Gas Sensing Applications