Optimizing the Design of Ultrasound Emitters for Energy Transfer to Millimeter-Scale Implantable Devices

Abstract

Wearable ultrasound emitters are used to power implanted devices or modulate neuronal function. Variation in placement of an external wearable can result in reduced efficiencies, improper stimulation of a biotarget, or inaccurate sensor readings. Using the K-Wave Toolbox in MATLAB a 10 kHz pulse was simulated to test different linear ultrasound emitter configurations were tested and the total pressure response of on an implanted lead zirconate titanate (PZT) device. The simulations covered pressure loss as the sensor moves away from center, pressure loss from distance between multiple emitters, and pressure loss from changing diameters of emitters. Desired performance specifications were a ≤ 10% pressure loss over a wide range of placements of an emitter, minimize power consumption, and should allow for ~25 mm (1 in) width where there is no pressure loss. After running multiple simulations, results showed that using a single emitter was more optimal than an array of multiple emitters. This was due to multiple emitters needing a less than 1mm distance between multiple emitters to achieve a less than 10% pressure loss. The size of the emitter chosen was to be 32mm in diameter. This was shown to give a 20 mm distance of zero percent pressure loss compared to a 5mm distance of a 16mm emitter. This diameter also has the same capacitance and impedance as a four-emitter array of 16mm diameter thus keeping power consumption the same. In conclusion a single 32mm diameter transducer provides optimal energy transfer for a PZT Sensor.

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