A 1.7mm³ MEMS-on-CMOS tactile sensor using human-inspired autonomous common bus communication

A bus-connected tactile sensor system composed of MEMS-CMOS integrated force sensors was developed. A capacitance-to-digital convertor for force sensing, a data reduction processor and a serial bus communication controller are implemented by a laboratory-designed ASIC (Application Specific Integrated Circuit). These functions enable the tactile sensor to be connected with a serial bus cable, and to autonomously transmit sensing data using CSMA (Carrier Sense Multiple Access) protocol. By applying a novel MEMS-CMOS integration technology, the integrated tactile sensor can be directly mounted on a flexible printed circuit board. The chip size is 2.54mm × 2.54mm × 0.27mm, i.e. 1.7mm³, and there are 20 through-silicon interconnection using saw-diced lateral tapered grooves. The digital data from the completed tactile sensor contains 32 bit force sensing data, which corresponds to an external force linearly. Data reduction processing based on threshold operation and adaptation inspired by tactile receptors was carried out to overcome packet collision problem. Finally, the serial bus network was demonstrated using three sensors to evaluate the network performance.