The increasing data rate has become a major issue confronting next-generation intracortical brain-machine interfaces (iBMIs). The scaling number of recording sites requires complex analog wiring and lead to huge digitization power consumption. Compressive event-based neural frontends have been used in high-density neural implants to support the simultaneous recording of more channels. Event-based frontends (EBF) convert recorded signals into asynchronous digital events via delta modulation and can inherently achieve considerable compression. But EBFs are prone to false events that do not correspond to neural and may affect the output firing rate, which is the key feature for neural decoding. Spike detection (SPD) is a key process in the iBMI pipeline to detect neural spikes and further reduce the data rate. However, conventional digital SPD suffers from the increasing buffer size and frequent memory access power, and conventional spike emphasizers are not compatible with EBFs. In this work we introduced an event-based spike detection (Ev-SPD) algorithm for scalable compressive EBFs. To implement the algorithm effectively, we proposed a novel low-power 10-T eDRAM-SRAM hybrid random-access memory (HRAM) in-memory computing (IMC) bitcell for event processing. We fabricated the proposed 1024-channel IMC SPD macro in a 65nm process and tested the macro with both synthetic dataset and Neuropixel recordings. The proposed macro achieved a high spike detection accuracy of 96.06% on a synthetic dataset and 95.08% similarity and 0.05 firing pattern MAE on Neuropixel recordings. Our event-based IMC SPD macro achieved a high per channel spike detection energy efficiency of 23.9 nW per channel and an area efficiency of 375 μm2 per channel. Our work presented a SPD scheme compatible with compressive EBFs for high-density iBMIs, achieving ultra-low power consumption with an IMC architecture while maintaining considerable accuracy.

Conductive Intracardiac Communication (CIC) uses cardiac tissue as a transmission medium for short-range wireless communication and is a potential method for enabling leadless multi-chamber pacing. However, the characterization of the intracardiac channel is significantly influenced by the experimental setup and conditions. The reported results in the literature vary depending on the measurement methods used, posing challenges in obtaining reliable channel characterization for CIC. In this paper, we aim to investigate the effects of different measurement devices and conditions on the intracardiac channel. By clarifying how impedance imbalance affects the gain measurement results, we design a weak-signal measurement circuit with high common-mode rejection. This new circuit provides a more accurate and effective gain measurement scheme for the CIC channel. An equivalent circuit model simulating cardiac biomechanical impedance is constructed to analyze how capacitive and resistive imbalances affect the gain measurement results. The effects of these imbalances are verified by intracardiac channel impedance imbalance experiments. A high common-mode rejection-high-resistance differential measurement circuit that can reduce the effects of capacitive and resistive imbalances simultaneously, is then designed to suppress the interference in the experiments. The results show that changes in the measurement equipment and isolation method lead to variations in the coupling circuit characteristics, causing differences of up to 16.65 dB in the measurement results. Experiments using the designed measurement circuits effectively mitigate interference from impedance imbalance on the measurement results. This study identifies the reasons behind the discrepancies in the experimental results of previous studies and provides a more reliable gain measurement scheme for CIC research.

Wireless implantable drug delivery systems (DDSs) enable targeted, on-demand drug release to maximize therapeutic efficacy. Ultrasound has been proposed to wirelessly power and control millimeter-sized deeply implantable DDSs, but initial demonstrations encountered challenges in power transfer and release control reliability in dynamic in vivo environments. In this work, we present a closed-loop implantable DDS using ultrasound wireless power and communication in conjunction with an electrochemical drug release mechanism. The system consists of piezoelectric transducers for wireless power and data transmission, a drug delivery module containing drug-loaded electroresponsive nanoparticles, and a custom CMOS integrated circuit for closed-loop drug release using a programmable potentiostat capable of providing potentials up to $\boldsymbol{\pm}$1.5 V and sensing current up to $\boldsymbol{\pm}$100 $\boldsymbol{\mu}$A. The chip also improves power transfer robustness by enabling ultrasound power combining and rectifier voltage feedback which can be used to adapt the power transmitter and minimize misalignment. Closed-loop release control is tested in vitro using the wirelessly powered DDS at 8cm depth by adjusting the potentiostat stimulus voltage based on feedback of redox current into fluorescein-loaded nanoparticles, resulting in consistent 2 $\boldsymbol{\mu}$g release across different fluorescein loading concentrations and a 39$\%$ reduction in release amount variation. These results demonstrate the effectiveness of closed-loop release control in enabling precise and reliable drug delivery.

This paper presents an adaptive active rectifier with digital feedback delay controllers (DFDC) which quickly tracks optimal on/off timing against input voltage and load variations. To efficiently generate the on/off transition, the proposed active rectifier adopts dynamically controlled coarse/fine delay lines rather than using conventional power-hungry static comparators, while removing the risk of unwanted multiple driving pulses to pass transistors. DFDC conducts the dual-loop digital feedback to independently adjust on/off timing with high-speed 13.56-MHz loop bandwidth, improving the voltage conversion ratio (VCR) and power conversion efficiency (PCE). DFDC can enable real-time power-saving mode control that automatically masks clock-toggling to non-essential blocks to minimize dynamic power loss while driving power transistors. To validate the efficacy of the proposed adaptive rectifier during digital feedback and settling procedures, experiments were carried out with 0.25 μm CMOS prototype at the carrier frequency of 13.56-MHz, input voltages between 1.7 and 2.6 V, and load ranges from 0.33 to 2.2 kΩ. The proposed active rectifier employing DFDC achieves a peak PCE of 93.5% and the peak VCR of 96.3% at the output power of 12.52 mW and 2.02 mW, respectively.

In recent years, pulsed magnetic field (PMF) have attracted significant attention as a non-invasive electroporation method in the biomedical field. To further explore the biomedical effects generated by oscillating PMF, we designed a novel PMF generator for biomedical research. Based on resonance principles, the designed generator outputs sinusoidal oscillating PMF. To validate the feasibility and application value of the designed topology, a miniaturized platform was constructed using a selected multi-turn solenoid coil. The output performance of the generator was tested under different discharge voltage levels. The results revealed that the current multiplication factor remained consistently around 2 times, with the energy efficiency and circuit quality factor maintained at 82% and above 4.5, respectively. In addition, the generator's ability to flexibly modulate the number of pulse oscillations was demonstrated. The compatibility of the designed coil parameters and generator circuit parameters was analyzed, with tests on the effects of coil resistance and switch action time on the generator's output performance. Based on the magnetic field action platform, a simulation model of the actual scale coil was established. The spatial and temporal distribution of the magnetic field, induced electric field, and power transmission in the target area were described from multiple angles. Finally, biological experiments conducted using the constructed generator revealed the synergistic effect of sinusoidal oscillating PMF combined with drugs in tumor cell killing.

This article describes a low noise and ultra-high input impedance active electrode (AE) interface chip for dry-electrode EEG recording. To compensate the input parasitic capacitance and the ESD leakage, power/ground/ESD bootstrapping is proposed. This design integrates chopping stabilization technique to suppress flicker noise of the amplifier which has never been tackled in previous bootstrapped AE design. Both on-chip and off-chip input routing is active shielded to minimize wire parasitic. Fabricated in a 0.18μm CMOS process, the AE core occupies about 0.056mm2 and draws 17.95μA from a 1.8V supply. The proposed AE achieves 100GΩ input impedance at 50Hz and over 1GΩ at 1kHz with a low input-referred noise of 382nVrms integrated from 0.5Hz to 70Hz. This design is the first 100GΩ@50Hz input impedance chopper stabilized AE compared to the state-of-the-art. Dry-electrode EEG recording capability of the proposed AE are verified on three types of experiments including spontaneous α-wave, event related potential and steady-state visual evoked potential.

Low-field nuclear magnetic resonance (NMR) instruments are an indispensable tool in industrial research and quality control. However, the intrinsically low spin polarization at low magnetic fields severely limits their detection sensitivity and measurement throughput, preventing their widespread use in biomedical analysis. Overhauser dynamic nuclear polarization (ODNP) effectively addresses this problem by transferring the spin polarization from free electrons to protons, significantly enhancing sensitivity. In this paper, we explore the potential of using ODNP for signal enhancement in a custom-designed portable chip-based DNP-enhanced NMR platform, which is centered around a miniaturized microwave (MW) transmitter, a custom-designed NMR-on-a-chip transceiver, and two application-specific ODNP probes. The MW transmitter provides frequency synthesis, signal modulation, and power amplification, providing sufficient output power for efficient polarization transfer. The NMR-on-a-chip transceiver combines a radio frequency (RF) transmitter with a fully differential quadrature receiver, providing pulsed excitation and NMR signal down-conversion and amplification. Two custom-designed ODNP probes are used for proof-of-concept DNP-enhanced NMR relaxometry and spectroscopy measurements. The presented chip-based ODNP platform achieves a maximum MW output power of , resulting in a signal enhancement of using the relaxometry ODNP probe with of non-degassed TEMPOL solution, and an enhancement of with the spectroscopy ODNP probe using of the same solution. The proton polarization was increased from to at a low field of . Proof-of-concept measurements on radical-doped tattoo inks and acetic acid verify the potential of our chip-based ODNP platform for the analysis of biologically and medically relevant parameters such as relaxation times, chemical shifts, and hyperfine interactions.