Frequency response of an inchworm motor fabricated with micromachined interlocking surface mesoscale actuator device (MAD)

The development and frequency response of a novel proof-of- concept prototype Mesoscale Actuator Device (MAD) is described in this paper. The MAD is similar to piezoelectric driven inchworm motors with the exception that mechanically interlocking microridges replace the traditional frictional clamping mechanisms. The interlocked microridges, microfabricated from single crystal silicon, are shown to support macroscopic loads. Tests conducted on the current design demonstrate that the interlocked microridges support 16 MPa in shear or that two sets of 3 X 5 mm locked chips support a 50 kgf. Operation of three generations of prototype MAD device containing microridges are accomplished at relatively large frequencies using an open loop control signal. Synchronizing the locking and unlocking of the microridges with the elongating and contracting actuator requires a dedicated waveform in the voltage signal supplied and permitted large operational frequencies. First generation operates at 0.6 Hz and demonstrated 1000s microridges can be engaged without problem, second generation moves like an inchworm up to 32 Hz, and the third generation including an external force was successfully operated from 0.2 Hz to 500 Hz corresponding to speeds from 2 micrometers /s to 5 mm/s. The upper limit (500 Hz) was imposed by software limitations and not related to physical limitations of the current device.