This brief presents an ultrasonically powered micro-system for deep tissue optogenetic stimulation. The developed system is composed of a Base for Powering and Controlling (BPC) and an implantable Dust for optogenetics and drug delivery. The Dust consists of a piezoelectric crystal, a rectifier chip, and a micro-scale custom-designed light-emitting-diode (μ LED) integrated, miniaturized, and envisioned to be used for freely moving animal studies. The proposed Dust operates in frequencies up to 5 MHz, power levels in the 0-10 mW range, achieves start-up within 1.8~μ s at 2.9 MHz operating frequency at 14.4 mW/mm2 ultrasound power density, and 98.1% chip efficiency at 2 mW input power. With the BPC implemented and attached to ( 500~μ m )3 PZT4 crystals, set to 60 V at 2.8 MHz operating frequency at 3 mm distance in demineralized water, the dust delivered up to 6 mW to its load (μ LED for optogenetics), which translates to 0.11% total system efficiency.

This letter presents an ultrasonically powered dual-wavelength optogenetic device that targets simultaneous excitation and inhibition of neural activities, or in a broader sense, optical stimulation in two distinct wavelengths for targeting different populations of neurons. This can be applied to a variety of neurological disorders. The device features a load regulator circuit that shares the available power budget between two LEDs in a power-efficient and controlled way suppressing the need for adaptive matching and overvoltage protection circuits. Furthermore, the regulator circuit is capable of detecting power burst availability on the device and generating a control signal, accordingly. For 5.25 -mW acoustic power at the device's surface, the rectified voltage, and the total current load of the system are regulated to 2.79 V and 600A , respectively. The maximum chip and device efficiencies of 92.5% and 31.8% are measured, respectively. The total die area in 180- nm CMOS technology nose and the estimated system volume are 0.16/2 and 0.572/3 , respectively.

A low-power mixed-signal IC for implantable pacemakers is presented. The proposed system features three independent intracardiac signal readout channels with pulse-width-modulated outputs. Also, the proposed system is capable of measuring the amplitude and phase of the bioimpedance with pulse-width-modulated outputs for use in rate adaptive pacemakers. Moreover, a stimulation system is embedded, offering 16 different amplitudes from 1 to 7.8&#x00A0;V. A backscattering transmitter transfers the output signals outside the body with very little power consumption. The proposed low-power mixed-signal IC is fabricated in a 0.18-&#x03BC;m HV CMOS process and occupies 2.38 mm2. The biopotential channels extract the heart signals with 9.2 effective number of bits and the bioimpedance channels measure the amplitude and phase of the heart impedance with 1.35 &#x03A9;<formula><tex>$_{rms}$</tex></formula> accuracy. The complete IC consumes only 4.2&#x00A0;&#x03BC;A from a 1-V power supply.

This paper presents an implantable bio-impedance measurement system for cardiac pacemakers. The fully integrated system features a lowpower analog front-end and pulse widthmodulated output. The bio-impedance readout benefits from voltage to time conversion to achieve a very low power consumption for wirelessly transmitting the data outside the body. The proposed IC is fabricated in a 0.18μmCMOSprocess and is capable ofmeasuring the bio-impedance at 2 kHz over a wide dynamic range from 100λ to 3.3 kλ with 1.35 λrms accuracy and 1 μA maximum current injection while consuming just 1.55 μA from a 1 V supply.