A CMOS Micromachined Gripper Array with On-Chip Optical Detection

This paper presents the design, fabrication, and characterization of CMOS micromachined grippers with on-chip optical detection. The CMOS MEMS fabrication features a combination of metal wet etch and sacrificial polysilicon etch for structural release. The fabricated microstructure contains metal and dielectric layers, plus a polysilicon heater for electrothermal actuation. Optical detection is provided by the photo detectors placed beneath the gripping sites. Dynamic characterization of a 200 mum-long microgripper shows a measured thermal time constant of 53 mus. For an applied power of 6 mW, one arm of the gripper produces a 3.6-mum in-plane displacement and a 1.6-mum out-of-plane displacement. The corresponding maximum heater temperature is 220degC, while the temperature elevation at the tip is only 28degC. The measured sensitivity and dynamic range of the photo detector are 1.42 V/lux-sec and 48.5 dB, respectively.