18.7 A remotely controlled locomotive IC driven by electrolytic bubbles and wireless powering
As implantable medical CMOS devices become a reality [1], motion control of such implantable devices has become the next challenge in the advanced integrated micro-system domain. With integrated sensors and a controllable propulsion mechanism, a micro-system will be able to perform tumor scan, drug delivery, neuron stimulation, bio-test, etc, in a revolutionary way and with minimum injury. Such devices are especially suitable for human hollow organs, such as urinary bladder and stomach. Motivated by the art reported in ISSCC 2012 [2], we demonstrate a remotely-controlled locomotive CMOS IC which is realized in TSMC 0.35μm technology. As illustrated in Fig. 18.7.1, a bare CMOS chip flipped on a liquid surface can be moved to the desired position without any wire connections. Instead of Lorentz forces [2], this chip utilizes the gas pressure resulting from electrolytic bubbles as the propulsive force. By appointing voltages to the on-chip electrolysis electrodes, one can decide the electrolysis location and thereby control the bubbles emissions as well as the direction of motion. With power management circuits, wireless receiver and micro-control unit (MCU), the received signal can be exploited as the movement control as well as wireless power. Experiments show a moving speed of 0.3mm/s of this chip. The total size is 21.2mm2 and the power consumption of the integrated circuits and the electrolysis electrodes are 125.4μW and 82μW, respectively.