A 0.065-mm³Monolithically-Integrated Ultrasonic Wireless Sensing Mote for Real-Time Physiological Temperature Monitoring

Application of a sub–0.1-mm 3 implantable mote for in vivo real-time wireless temperature sensing

“…In addition to providing power, the imager communicates to the mote with acoustic backscattering ( 21 ) through modulation of the on-chip PZT transducer electrical load. The IC itself [see note S1 for detailed circuit schematics and elaboration on circuit design can be found elsewhere ( 36 )] leverages low-power design approaches by operating most of its transistors in the subthreshold regime [with a gate-source voltage of around 0 V ( 39 )], reducing power consumption to only ~0.8 nW at physiological temperature (37°C). To overcome the variations of the incoming ultrasound power, the IC features a power-regulating block at the front end for converting the harvested energy from the PZT transducer to a regulated, constant voltage with a conversion efficiency of better than 71%.…”

“…Such modulation causes the amplitude of the reflected ultrasound echo to vary in the same frequency as the oscillator. At the ultrasound imager, temperature measurements are made by measuring this oscillation frequency, which shows an exponential relationship with temperatures in the form of , where f is the frequency, T is absolute temperature, and A and B are two process-related, temperature-independent constants ( 36 ). A fitting curve can be obtained by calibrating at two different temperatures, and any temperature can be calculated using this fitting curve and the detected oscillation frequency.…”

“…A fitting curve can be obtained by calibrating at two different temperatures, and any temperature can be calculated using this fitting curve and the detected oscillation frequency. In addition, the front-end power regulation results in a temperature error of only 0.088°C ( 36 ) within a wide input power range from 0.07 to 0.25 mW/mm 2 , expressed as spatial-peak temporal-average intensity ( I SPTA ).…”

Monitoring deep-tissue oxygenation with a millimeter-scale ultrasonic implant

“…The copyright holder for this preprint this version posted March 5, 2021. ; https://doi.org/10.1101/2021.03.05.434129 doi: bioRxiv preprint 5 monitoring of physiological parameters such as temperature 29 and pressure 30 . Here, we present a system for direct tissue O 2 monitoring that integrates ultrasound (US) technology with a luminescence sensor, demonstrating, for the first time to our knowledge, continuous real-time in vivo O 2 measurements at centimeter-scale depths in a clinically-relevant, anesthetized sheep (large animal) model and operation at great depths (≥ 5 cm) through ex vivo porcine (anatomically heterogeneous) tissue.…”

“…During the last decade, implantable systems based on ultrasonic mm-sized implants have demonstrated in vivo electrical neural recording 20 from and stimulation 21 of the sciatic nerve in an anesthetized rat model, in vivo tumor oxygenation in an anesthetized mouse pancreatic tumor model 27 , photodynamic therapy of tumor in an anesthetized mouse model 28 and in vitro monitoring of physiological parameters such as temperature 29 and pressure 30 . Here, we present a system for direct tissue O 2 monitoring that integrates ultrasound (US) technology with a luminescence sensor, demonstrating, for the first time to our knowledge, continuous real-time in vivo O 2 measurements at centimeter-scale depths in a clinically-relevant, anesthetized sheep (large animal) model and operation at great depths (≥ 5 cm) through ex vivo porcine (anatomically heterogeneous) tissue.…”