Wei Wang

Wireless communication technologies for bioelectronic implants enable remote monitoring for diagnosis and adaptive therapeutic intervention without the constraints of wired connections. However, wireless data uplink from millimeter-scale devices deep in the body struggles to achieve low power consumption while maintaining large misalignment tolerances. Here, we report a passive wireless backscatter communication system based on magnetoelectric transducers that consumes less than 0.3 pJ/bit and achieves less than 1E-6 bit error rate at a distance of 55 mm while tolerating a misalignment of 10 mm. Using this robust data uplink, we designed a wireless cardiac sensing node that can transmit electrocardiogram signals from the beating heart surface of a porcine model to a custom external transceiver using the magnetoelectric backscatter uplink. This reliable, near-zero-power communication method provides opportunities for next-generation bioelectronics to feature real-time physiological monitoring and closed-loop therapies while maintaining a small form factor and low power consumption.

Accurate, low-power, and compact temperature sensors are demanded in a wide range of biomedical, environmental, and industrial sensing applications. This article presents an accurate and precise CMOS temperature sensor based on a sub-threshold ring oscillator (RO) in 180 nm. The sensing core employs a five-stage super cut-off contention-free (SCCF) delay cell to closely mimic the temperature dependency of a single MOSFET, minimizing the errors in current-to-frequency conversion and achieving a ${-} 0.065~^{\circ }$ C/ ${+} 0.061~{^{\circ }}$ C inaccuracy after 2-point calibration and ${\pm } 0.26~{^{\circ }}$ C after 1-point calibration from ${-} 20~{^{\circ }}$ C to $100~{^{\circ }}$ C. Meanwhile, a self-biased 3-transistor (3T) header significantly reduces the supply line sensitivity to $0.02~{^{\circ }}$ C/V and achieves less than $0.2~{^{\circ }}$ C temperature drift after more than 180 h of accelerated aging. The aging-induced drift is reduced to $0.11~{^{\circ }}$ C with a calibration after 30 h of pre-aging. Additionally, this work introduces an adaptive uniform resolution counter to maintain a consistent and programmable resolution across the wide temperature range, despite the sub-threshold RO’s exponential dependency on temperature. The prototyping sensor in 180-nm CMOS consumes only 33 nW at $20~{^{\circ }}$ C and occupies 0.028- $\text {mm}^{2}$ area. Beyond standard circuit testing, the 1-pt calibrated sensor was validated in a multi-day in vivo animal body temperature tracking experiment and outperformed off-the-shelf solutions.

Biomedical implants offer transformative tools to improve medical outcomes. To realize minimally invasive implants with miniaturized volume and weight, wireless power transfer (WPT) has been extensively studied to replace bulky batteries that dominate the volume of traditional implants and require surgical replacements. Ultrasonic (US) and magnetoelectric (ME) WPT modalities, which leverage low-frequency acoustic–electrical coupling for energy transduction, become viable solutions for millimeter-scale receivers (RXs). This work presents a fully integrated power management unit (PMU) for ME WPT in millimetric implants. The PMU achieves load-independent maximum power extraction and usage by continuously matching the transducer’s impedance, dynamically optimizing the power stage across varying input/load conditions, and reusing the storage energy to sustain the system when input power drops. Its parallel-input regulation and storing stages architecture prevents the cascading power loss. With the skewed-duty-cycle maximum power point tracking (MPPT) technique and regulation efficiency optimizer, the PMU achieves a peak MPPT efficiency of 98.5% and a peak system overall efficiency of 73.33%. Additionally, the PMU includes an adaptive high-voltage (HV) charging stage that charges the stimulation capacitor up to 12 V with an improved efficiency of 37.88%.

Wearable photoacoustic imaging devices hold great promise for continuous health monitoring and point-of-care diagnostics. However, the large data volume generated by high-density transducer arrays presents a major challenge for realizing compact and power-efficient wearable systems. This article presents a photoacoustic imaging receiver (RX) that embeds compressive sensing directly into the hardware to address this bottleneck. The RX integrates 16 AFEs and four matrix-vector-multiplication (MVM) SAR ADCs that perform energy- and area-efficient analog-domain compression. The architecture achieves a $4\times $ – $8\times $ reduction in output data rate while preserving low-loss full-array information. The MVM SAR ADC executes passive and accurate MVM using user-defined programmable ternary weights. Two signal reconstruction methods are implemented: 1) an optimization approach using the fast iterative shrinkage-thresholding algorithm and 2) a learning-based approach employing implicit neural representation. Fabricated in 65-nm CMOS, the chip achieves an ADC’s signal-to-noise-distortion ratio (SNDR) of 57.5 dB at 20.41 MS/s, with an analog front-end (AFE) input-referred noise of 3.5 nV/ $\mathbf {(\text {Hz})^{1/2}}$ . MVM linearity measurements show $R^{2} \gt 0.999$ across a wide range of weights and input amplitudes. The system is validated through phantom imaging experiments, demonstrating high-fidelity image reconstruction under up to $8\times $ compression. The RX consumes 5.83 mW/channel and supports a general ternary-weighted measurement matrix, offering a compelling solution for next-generation miniaturized, wearable PA imaging systems.

Miniature bioelectronic implants promise revolutionary therapies for cardiovascular and neurological disorders. Wireless power transfer (WPT) is a significant method for miniaturization, eliminating the need for bulky batteries in today’s devices. Despite successful demonstrations of millimetric battery-free implants in animal models, the robustness and efficiency of WPT are known to degrade significantly under misalignment incurred by body movements, respiration, heart beating, and limited control of implant orientation during surgery. This article presents an omnidirectional WPT platform for millimetric bioelectronic implants, employing the emerging magnetoelectric (ME) WPT modality, and “magnetic field steering” technique based on multiple transmitter (TX) coils. To accurately sense the weak coupling in a miniature implant and adaptively control the multicoil TX array in a closed loop, we develop an active echo (AE) scheme using a tiny coil on the implant. Our prototype comprises a fully integrated 14.2 mm3 implantable stimulator embedding a custom low-power system-on-chip (SoC) powered by an ME film, a TX with a custom three-channel AE RX chip, and a multicoil TX array with mutual inductance cancellation. The AE RX achieves −161 dBm/Hz input-referred noise with 64 dB gain tuning range to reliably sense the AE signal, and offers fast polarity detection for driver control. AE simultaneously enhances the robustness, efficiency, and charging range of ME WPT. Under 90° rotation from the ideal position, our omnidirectional WPT system achieves $6.8{ \times }$ higher power transfer efficiency (PTE) than a single-coil baseline. The tracking error of AE negligibly degrades the PTE by less than 2% from using ideal control.

Wireless minimally invasive bioelectronic implants enable a wide range of applications in healthcare, medicine, and scientific research. Magnetoelectric (ME) wireless power transfer (WPT) has emerged as a promising approach for powering miniature bio-implants because of its remarkable efficiency, safety limit, and misalignment tolerance. However, achieving low-power and high-quality uplink communication using ME remains a challenge. This paper presents a pulse-width modulated (PWM) ME backscatter uplink communication enabled by a switched-capacitor energy extraction (SCEE) technique. The SCEE rapidly extracts and dissipates the kinetic energy within the ME transducer during its ringdown period, enabling time-domain PWM in ME backscatter. Various circuit techniques are presented to realize SCEE with low power consumption. This paper also describes the high-order modeling of ME transducers to facilitate the design and analysis, which shows good matching with measurement. Our prototyping system includes a millimeter-scale ME implant with a fully integrated system-on-chip (SoC) and a portable transceiver for power transfer and bidirectional communication. SCEE is proven to induce >50% amplitude reduction within 2 ME cycles, leading to a PWM ME backscatter uplink with 17.73 kbps data rate and 0.9 pJ/bit efficiency. It also achieves 8.5 × 10 ^-5 bit-error-rate (BER) at a 5 cm distance, using a lightweight multi-layer-perception (MLP) decoding algorithm. Finally, the system demonstrates continuous wireless neural local-field potential (LFP) recording in an in vitro setup.

A $2\times56$ Gb/s 0.78-pJ/b four pulse-amplitude modulation (PAM-4) single-ended multiple-input multiple-output (MIMO) crosstalk cancellation and signal reutilization (XTCR) receiver (RX) is investigated for medium-reach (MR) backplane communications. An XTCR scheme based on active crosstalk extraction (A-XTCR) is proposed to improve the signal reutilization efficiency of the RX. By adopting the proposed asymmetric-inductor current-mode logic (CML) single-ended-to-differential (S2D) converter, the pseudo-differential output mismatch is alleviated. Fabricated in 28-nm CMOS, the RX achieves a bit error rate (BER) of $< 1\text{e}\,\,-10$ at 56-Gb/s PAM-4 transmission with a channel of 24-dB Nyquist loss. Compared with the XTCR based on the conventional passive crosstalk extraction (P-XTCR), the proposed A-XTCR technique has improved vertical and horizontal eye openings of the RX by 24% and 15% at 56-Gb/s PAM-4, respectively. The result corresponds to the best energy efficiency of 0.78 pJ/b/lane, which compares favorably with the state of the art.