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There has been increasing interest in wireless, miniaturized implantable medical devices for in vivo and in situ physiological monitoring. Here, we present such an implant that uses a conventional ultrasound imager for wireless powering and data communication and acts as a probe for real-time temperature sensing, including the monitoring of body temperature and temperature changes resulting from therapeutic application of ultrasound. The sub–0.1-mm3, sub–1-nW device, referred to as a mote, achieves aggressive miniaturization through the monolithic integration of a custom low-power temperature sensor chip with a microscale piezoelectric transducer fabricated on top of the chip. The small displaced volume of these motes allows them to be implanted or injected using minimally invasive techniques with improved biocompatibility. We demonstrate their sensing functionality in vivo for an ultrasound neurostimulation procedure in mice. Our motes have the potential to be adapted to the distributed and localized sensing of other clinically relevant physiological parameters.

Background Opioid-related deaths are a leading cause of accidental death, with most occurring in patients receiving chronic pain therapy. Respiratory arrest is the usual cause of death, but mechanisms increasing that risk with increased length of treatment remain unclear. Repeated administration produces tolerance to opioid analgesia, prompting increased dosing, but depression of ventilation may not gain tolerance to the same degree. This study addresses differences in the degree to which chronic morphine (1) produces tolerance to ventilatory depression versus analgesia and (2) alters the magnitude and time course of ventilatory depression. Methods Juvenile rats received subcutaneous morphine for 3 days (n = 116) or vehicle control (n = 119) and were then tested on day 4 following one of a range of morphine doses for (a) analgesia by paw withdraw from heat or (b) respiratory parameters by plethysmography–respirometry. Results Rats receiving chronic morphine showed significant tolerance to morphine sedation and analgesia (five times increased ED50). When sedation was achieved for all animals in a dose group (lowest effective doses: opioid-tolerant, 15 mg/kg; opioid-naive, 3 mg/kg), the opioid-tolerant showed similar magnitudes of depressed ventilation (−41.4 ± 7.0%, mean ± SD) and hypercapnic response (−80.9 ± 15.7%) as found for morphine-naive (−35.5 ± 16.9% and −67.7 ± 15.1%, respectively). Ventilation recovered due to tidal volume without recovery of respiratory rate or hypercapnic sensitivity and more slowly in morphine-tolerant. Conclusions In rats, gaining tolerance to morphine analgesia does not reduce ventilatory depression effects when sedated and may inhibit recovery of ventilation.

Abstract-Magnetic resonance coupling is a widely used technique for wireless power transfer (WPT) in biomedical and consumer electronics applications. For specific applications, device size limits the overall size of the transmit and receive coils. In this work, design considerations for an asymmetrical 4-element WPT system are investigated. For either a target efficiency or a desired WPT range, the optimal coil parameters such as Q and coupling coefficient are defined and these design considerations are experimentally verified. The results can be used to design an optimal set of coils for various WPT applications.

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This paper explores the extent to which a solid-state transmitter can be miniaturized, while still using RF for wireless information transfer and working with power densities and operating voltages comparable to what could be harvested from a living system. A 3.1 nJ/bit pulsed millimeter-wave transmitter, 300 by 300 by 250 in size, designed in 32-nm SOI CMOS, operates on an electric potential of 130 mV and 3.1 nW of dc power. Farfield data transmission at 33 GHz is achieved by supply-switching an LC-oscillator with a duty cycle of . The time interval between pulses carries information on the amount of power harvested by the radio, supporting a data rate of 1 bps. The inductor of the oscillator also acts as an electrically small on-chip antenna, which, combined with millimeter-wave operation, enables the extremely small form factor.Index Terms-Antennas, low power design, monolithic integrated circuits, radio frequency oscillators. 1549-8328

This paper describes an inexpensive pico-projector-based augmented reality (AR) display for a surgical microscope. The system is designed for use with Micron, an active handheld surgical tool that cancels hand tremor of surgeons to improve microsurgical accuracy. Using the AR display, virtual cues can be injected into the microscope view to track the movement of the tip of Micron, show the desired position, and indicate the position error. Cues can be used to maintain high performance by helping the surgeon to avoid drifting out of the workspace of the instrument. Also, boundary information such as the view range of the cameras that record surgical procedures can be displayed to tell surgeons the operation area. Furthermore, numerical, textual, or graphical information can be displayed, showing such things as tool tip depth in the work space and on/off status of the canceling function of Micron.

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