A remotely powered implantable microsystem for continuous blood glucose monitoring is presented. The microsystem consists of a microfabricated glucose biosensor flip-chip bonded to a transponder chip. The transponder chip is inductively powered by an external reader with a 13.56-MHz carrier. It then measures the output signal of the glucose biosensor and transmits the measured data back to the external reader using load-shift keying (LSK). The microsystem has a volume of 32 mm(3). The procedures for the microfabrication of the glucose sensor and the assembly of the microsystem are described along with the description of the circuit blocks of the transponder chip. The transponder chip has been fabricated with the TSMC 0.18-mum CMOS process and has a total area of 1.3 x 1.3 mm(2). The chip can measure the sensor output current ranging from 1 nA to 1 muA with less than 0.3% nonlinearity error, provided that the amplitude of the received RF signal is higher than 2.6 V; the circuit consumes a total current of about 110 muA.
As mobile robots become increasingly autonomous over extended periods of time, opportunities arise for their use on repetitive tasks. We define and implement behaviors for a class of such tasks that we call continuous area sweeping tasks. A continuous area sweeping task is one in which a robot (or group of robots) must repeatedly visit all points in a fixed area, possibly with non-uniform frequency, as specified by a task-dependent cost function. Examples of problems that need continuous area sweeping are trash removal in a large building and routine surveillance. We present a formulation for this problem and an initial algorithm to address it. The approach is analyzed analytically and is fully implemented and tested, both in simulation and on a physical robot.
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