CMOS micromachined grippers with on-chip optical detection

This paper presents the design, fabrication and characterization of CMOS (complementary metal oxide semiconductor) micromachined grippers with on-chip photo detectors placed beneath the gripping sites. The 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. For an applied power of 6 mW, one arm of the gripper produces a 3.6 µm in-plane displacement and a 1.6 µm out-of-plane displacement. The corresponding heater temperature is 220 °C, and the temperature elevation at the tip is only 28 °C. The measured sensitivity and dynamic range of the photo detector are 1.42 V lux−1 s and 48.5 dB, respectively. For measurements with and without grabbing a polystyrene bead, the difference of sensed voltages is 0.06 V at 100 lux.