Implantable medical devices (IMDs) can greatly assist in managing health and preventing disease. Anatomical constraints limit the size of IMDs and many applications are infeasible due to the large required batteries or inductive powering antennas. The proposed work seeks to improve wireless power transfer efficiency and reduce power consumption in IMDs thereby increasing achievable implant depth and decreasing device size. Two major innovations will allow improved power transfer efficiency: (1) Electromagnetic IMD Location Estimation and (2) Directed Power Transmission. The location of the IMD will be estimated by extracting spatial information from variations in the backscattered signal across an external antenna array. It is proposed to: recover that backscattered signal by exploiting amplifier unilateralism and differential antennas; investigate how many antennas are required to estimate the location of the IMD; and to devise efficient algorithms to perform that location estimation. Circuits and algorithms to direct power to an IMD in the intermediate field which has been shown recently to be the optimum field regime for powering a broad class of IMDs are proposed. Power consumption in IMD applications is often dominated by signal acquisition. Two signal acquisition circuit thrusts will enable lower IMD power consumption: (1) Bio Signal Adaptive Amplifier and (2) Analog to Digital Converter (ADC) Architectures for lower power at moderate resolutions. Thus far information lossless power adaptation has been demonstrated only for ADCs in motor neuron sensing applications. Circuits and algorithms to generalize the method to amplifiers and to broader classes of applications are proposed. Capacitor mismatch in a successive approximation ADC will be reduced through a reconfigurable capacitor array leading to a substantial decrease in ADC area and power. Additionally, a low power ADC architecture based on binary search of time delays is proposed.
Broader Impacts The primary broader impact of this program will be to enable smaller IMDs at greater implant depths thus enabling a broad class of new IMDs such as sub-mm implanted drug delivery devices and distributed neurosensors which should have very positive impacts in health care. The IMD location and orientation estimate will allow better interpretation of sensed data. The proposed ADC architectures will be useful in much of electronics, whenever moderate resolution low power ADCs are required. The findings will be published in leading journals. A major part of this proposal is the STEM outreach plan to expand Prof O?Driscoll?s previous K-12 outreach, which has received written commendation from the California State Legislature.
