The elimination of batteries in implants enables their miniaturization to millimeter (mm) scale. This can be achieved by wireless power transfer (WPT), which is also beneficial for the long-term operation of implants. Current state-of-the-art WPT techniques include inductive coupling, ultrasound (US), and magnetoelectric (ME) modalities. US and ME links operate at acoustic wave resonance, working at low frequencies (100s of kHz to several MHz) while using mm-scale receivers. In contrast, mm-scale inductive links are efficient at high frequencies as they operate at electromagnetic wave resonance. While all three modalities are attractive, the literature lacks a comparative study in which these modalities are evaluated under similar conditions (size and depth of implant) when they are optimized and operate under regulatory safety limits. This paper compares the power receiving capability of ~ 6.2×2.2×1.4 mm3ME and US receivers, and an inductive coil with comparable 20 mm3volume and 3 mm2surface area. In measurements at a 30 mm depth within a tissue medium, the inductive, ME, and US WPT links could deliver 7.7 mW, 7 mW, and 15.55 mW of power considering the safety limits, respectively. Among these modalities, the ME link demonstrated the highest robustness against angular misalignment.

Structural health monitoring (SHM) offers extended structural lifespan, cost savings, and early risk detection, ultimately contributing to enhanced overall performance of critical structures. This paper presents a multiplexed active ultrasonic node for generating ultrasonic waves using a piezoelectric transducer powered by a single optical fiber (driven by a tunable laser) towards distributed SHM with no complex wiring. The proof-of-concept prototype is built using commercial off-the-shelf components on a 41×33 mm2printed circuit board. In measurements, 2.75 mW of power is harvested by two parallelly connected Germanium photodiodes across a portion of the optical fiber with long period fiber Bragg grating at 1554 nm wavelength. This power is used to drive a piezoelectric transducer by five ~ 30 V pulses at 500 kHz. A method to program the number of driving pulses is also presented. Power scheduling technique ensures operation with limited available input voltage and power of hundreds of mV and a few mW, respectively.

This paper introduces a technique, called monotonic energy transmission (MET), for short-range wireless data transfer from small implantable devices with millimeter (mm) scale dimensions to an external unit using the magnetoelectric (ME) effect. In the proposed technique, while low-frequency magnetic field is used to power an implant which integrates a small ME transducer, data is transferred by driving the ME transducer with an initiation and a suppression sinusoid, which are 180° apart in phase. Transmitting both sinusoids improves the data rate and minimizes the inter-symbol interference (ISI). This technique was combined with pulse position modulation (PPM) to further increase the data rate. This paper describes the theory behind the proposed technique and demonstrates its operation through measurements using a$6.56\times 2.63\times 0.67 \ \text{mm}^{3}$ME transducer fabricated with Metglas and PZT-5A as the magnetostrictive and piezoelectric layers, respectively. In measurements, 220 kbps data rate was achieved using a delay detection resolution of 1 ns with an ME transducer operating at 274 kHz.

To counter the threats of reverse engineering (RE) and Trojan in-sertion, researchers have considered gate-level obfuscation in inte-grated circuits (IC) as a viable solution. However, several techniques are present in the literature to crack the obfuscation with varying degree of success raising the concern about their secrecy. In this article, we have presented TOIC (Timing Obfuscated Integrated Circuits), a novel technique where sequential elements are obfuscated to hide the true timing paths in the design. TOIC can act as a standalone countermeasure against IC reverse engineering or can be incorporated with existing gate camouflaging techniques to maximize adversarial RE effort. Previous research has shown that limiting access to internal nodes can improve the adversarial RE effort at the cost of poor testability. TOIC can impose prohibitively large decamouflaging time complexity by limiting the controllability and observability over the internal nodes in an IC while preserving complete testability.