MEMS/NEMS sensors are increasingly popular because of their small weight and size. They can be used to improve the performance and decrease the power consumption during the operation of nanosatellites, jet planes, cars, cell phones, to mention a few, where size and weight matters. The industries are pressing for advancement in the fast emerging field.
Projects
- Characterization of mechanical properties
- Modeling and optimization of uncooled micromachined bolometers
- Linearly tunable MEMS capacitors
- Novel thermal microactuators
Microactuators are the key devices allowing MEMS to perform physical functions by converting input energy into output force and motion. Among various microactuators, thermal expansion-based microactuators (shortly thermal microactuators) feature high mechanical force and large static displacement. Despite these advantages, they can only be driven at relatively low frequencies. This limitation on the maximum actuation frequency of thermal microactuators originates from their dependence on heat transfer rate, which limits their effective bandwidth to low frequencies, usually less than 1 KHz.
This inherent limitation of thermal microactuators has inspired us to look at very basic principles of thermal excitation in order to find a possible way to increase their operational frequencies by changing the one-to-one correspondence between the actuation input and output signal. As a viable solution, we have come up with a new design for thermal microactuators that operates at twice the frequency of input signal. From a dynamic point of view, the new design features a complete out-of-plane motion cycle (including upward then downward strokes with perfect smooth switching between the two directions) when temperature monotonically changes. This suggests that the new microactuator has the potential of showing two output cycles per one cycle of input signal.
To verify the new design concept experimentally, various test specimens are fabricated using the PolyMUMPs® foundry process (Fig. 3). Thermal loading experiments have been carried out using an external heat source. The deformations of the test specimens are measured by an optical profiler. The experimental results have successfully demonstrated the expected reciprocating bending behavior of the microcantilever tip and showed good agreement with the predictions of numerical simulations.
