Acoustic impedance-matched surfaces do not reflect incident waves. Traditional means of acoustic absorption have so far resulted in imperfect impedance matching and bulky structures, or require costly and sophisticated electrical design. Inspired by electromagnetic metamaterials, a subwavelength acoustically reflecting surface with hybrid resonances and impedance-matched to airborne sound at tunable frequencies is now demonstrated.

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Acoustic metasurface with hybrid resonances

A major challenge for implantable medical systems is the inclusion or reliable delivery of electrical power. We use ultrasound to deliver mechanical energy through skin and liquids and demonstrate a thin implantable vibrating triboelectric generator able to effectively harvest it. The ultrasound can induce micrometer-scale displacement of a polymer thin membrane to generate electrical energy through contact electrification. We recharge a lithium-ion battery at a rate of 166 microcoulombs per second in water. The voltage and current generated ex vivo by ultrasound energy transfer reached 2.4 volts and 156 microamps under porcine tissue. These findings show that a capacitive triboelectric electret is the first technology able to compete with piezoelectricity to harvest ultrasound in vivo and to power medical implants.

Transcutaneous ultrasound energy harvesting using capacitive triboelectric technology

In situ bioremediation of monoaromatic pollutants in groundwater : A review

Neural implants have emerged over the last decade as highly effective solutions for the treatment of dysfunctions and disorders of the nervous system. These implants establish a direct, often bidirectional, interface to the nervous system, both sensing neural signals and providing therapeutic treatments. As a result of the technological progress and successful clinical demonstrations, completely implantable solutions have become a reality and are now commercially available for the treatment of various functional disorders. Central to this development is the wireless power transfer (WPT) that has enabled implantable medical devices (IMDs) to function for extended durations in mobile subjects. In this review, we present the theory, link design, and challenges, along with their probable solutions for the traditional near-field resonant inductively coupled WPT, capacitively coupled short-ranged WPT, and more recently developed ultrasonic, mid-field, and far-field coupled WPT technologies for implantable applications. A comparison of various power transfer methods based on their power budgets and WPT range follows. Power requirements of specific implants like cochlear, retinal, cortical, and peripheral are also considered and currently available IMD solutions are discussed. Patient's safety concerns with respect to electrical, biological, physical, electromagnetic interference, and cyber security from an implanted neurotech device are also explored in this review. Finally, we discuss and anticipate future developments that will enhance the capabilities of current-day wirelessly powered implants and make them more efficient and integrable with other electronic components in IMDs.

Wireless Power Transfer Strategies for Implantable Bioelectronics

Recently, implantable devices have become widely used in neural prostheses because they eliminate endemic drawbacks of conventional percutaneous neural interface systems. However, there are still several issues to be considered: low-efficiency wireless power transmission; wireless data communication over restricted operating distance with high power consumption; and limited functionality, working either as a neural signal recorder or as a stimulator. To overcome these issues, we suggest a novel implantable wireless neural interface system for simultaneous neural signal recording and stimulation using a single cuff electrode. By using widely available commercial off-the-shelf (COTS) components, an easily reconfigurable implantable wireless neural interface system was implemented into one compact module. The implantable device includes a wireless power consortium (WPC)-compliant power transmission circuit, a medical implant communication service (MICS)-band-based radio link and a cuff-electrode path controller for simultaneous neural signal recording and stimulation. During in vivo experiments with rabbit models, the implantable device successfully recorded and stimulated the tibial and peroneal nerves while communicating with the external device. The proposed system can be modified for various implantable medical devices, especially such as closed-loop control based implantable neural prostheses requiring neural signal recording and stimulation at the same time.

https://www.mdpi.com/1424-8220/18/1/1/pdf

An Implantable Wireless Neural Interface System for Simultaneous Recording and Stimulation of Peripheral Nerve with a Single Cuff Electrode.

Ultrasonic transcutaneous energy transfer using a continuous wave 650 kHz Gaussian shaded transmitter.

A high-speed 64-bit comparator using two-phase clocking dynamic CMOS logic with modified noninverting all-N-transistor block is presented. The pull-up charging and pull-down discharging of a comparator unit are accelerated by inserting two feedback MOS transistors between the evaluation N-block and the output. Detailed simulation results reveal appropriate L/W guidelines for the all-N-transistor block design. To increase throughput a parallel tree structure with two-phase clocks is employed. The comparator units of two adjacent layers are triggered by two out-of-phase clocks so that their individual outputs are pipelined without using extra hardware, e.g. latches. The operating clock frequency is 1.0 GHz while the compared output of two 64-bit binary numbers is done in 3.5 cycles.

1 GHz 64-bit high-speed comparator using ANT dynamic logic with two-phase clocking

Control of BTEX migration by intrinsic bioremediation at a gasoline spill site

This study presents an implantable microcontroller-based bi-directional transmission system with an inductive link designed for biological signal sensing. The system comprises an external module and an implantable module. The external module incorporates a high-efficiency class-E transceiver with amplitude modulation scheme and a data recovery reader. The transceiver sends both power and commands to the implanted module, while the reader recovers the recorded biological signal data and transmits the data to a personal computer (PC) for further data processing. To reduce the effects of interference induced by the 2 MHz carrier signal, the implanted module uses two separate coils to perform the necessary two-way data transmission. The outward backward telemetry circuitry of the implanted module was based on the load-shift keying (LSK) technique. The transmitted sensed signal had a 10-bit resolution and a read-out rate of 115 kbps. The implanted module, measuring 4.5 ? 3 ? 1.2 cm3, was successfully verified in animal experiment in which the electroneurogram (ENG) signal was recorded from the sciatic nerve of New Zealand rabbits in response to nociceptive stimulation of foot. The reliable operating distance of the system was within about 3.5 cm with an efficiency of around 25%. Our present study confirms that the proposed biological signal sensing device is suitable for various implanted applications following an appropriate biocompatible packaging procedure.

/pdf/an-implantable-bi-directional-wireless-transmission-system-1hko4cp1i0.pdf

An implantable bi-directional wireless transmission system for transcutaneous biological signal recording.

We present a novel implementation for 2K/8K dual-mode FFT (fast Fourier transform) for OFDM (orthogonal frequency division multiplexing) of DVB-T (digital video broadcasting terrestrial) receivers. Besides pipelining the FFT to reduce the area and enhance the data throughput, SDF (single-path delay feedback) butterfly units for radix-2 and radix-4 processing are adopted to resolve the power consumption difficulty and the P&R (place and route) problem. The SRAM is used in the butterfly units to relax the auto-refreshing requirement if DRAM is used such that not only is the dynamic power saved, the timing control is also less stingy. The 2K/8K FFT comprises 5/6 cascaded stages of radix-4 and one stage of radix-2 butterfly units. The proposed design is carried out by 0.35 /spl mu/m 2P4M CMOS process to verify the high processing 8 MHz rate with power dissipation as low as 535 mW at a 16 MHz system clock.

Chua-Chin Wang

Papers

Ultrasonic transcutaneous energy transfer using a continuous wave 650 kHz Gaussian shaded transmitter.

1 GHz 64-bit high-speed comparator using ANT dynamic logic with two-phase clocking

Control of BTEX migration by intrinsic bioremediation at a gasoline spill site

An implantable bi-directional wireless transmission system for transcutaneous biological signal recording.

A 2K/8K mode small-area FFT processor for OFDM demodulation of DVB-T receivers