IEEE transactions on biomedical circuits and systems最新文献

We present the TENSmini, a compact and wearable device (38 × 38 × 21 mm³, weighing only 31 g), designed for home-based self-management of overactive bladder syndrome (OAB). The device integrates two conductive textile electrodes into a sock, which can be washed and reused. It is wirelessly controlled with mobile devices to generate current pulses with adjustable frequency from 1 to 100 Hz, pulse width of 50 to 250 μs, and amplitude of up to 60 mA. A safety-enhanced drive circuit with galvanic isolation and automatic detection mechanism monitors electrode connections, prevents over-current, and protects users against open-circuit conditions. We report on the electrical properties of the conductive textile electrodes and present results from a real-world study involving ten human participants. The findings confirm that the wearable device effectively stimulates the tibial nerve and performs comparable to a clinical-grade stimulator. In general, the proposed system shows potential for OAB management due to its wearability, improved safety features, and long-term reusability.

Integrate-and-fire (I&F) neurons used in neuromorphic systems are traditionally optimized for low energy-per-spike and high density, often excluding the complex dynamics of biological neurons. Limited dynamics cause missed opportunities in applications such as modeling time-varying physical systems, where using a small number of neurons with rich nonlinearities can enhance network performance, even when rich neurons incur a marginally higher cost. By adding additional coupling into the gate of one transistor within an I&F neuron, we parsimoniously achieve a highly nonlinear system capable of exhibiting rich dynamics and chaos. The dynamics of this novel neuron include regular spiking, fast spiking, and chaotic chattering, and can be tuned via the neuron parameters and input current. We implement and experimentally demonstrate the behavior of our chaotic neuron and its subcircuits on a 350 nm field-programmable analog array. Experimental insights inform a compact simulation model, which validates experimental results and confirms that the additional coupling incites chaos. Results are corroborated with comparisons to traditional I&F neurons. Our chaotic circuit achieves the lowest area (0.0025 mm²), power draw (1.1-2.6 μW), and transistor count (6T) of any nondriven chaotic system in integrated CMOS thus far. We also demonstrate the utility of our neuron for neuroscience exploration and hardware security.

This paper proposes a motion-artifact-tolerant multi-channel biopotential-recording IC. A simple counter-based digital-assisted loop (DAL), implemented entirely with digital circuits, is proposed to track motion artifacts. The DAL effectively tracks motion artifacts without signal loss for amplitudes up to 120 mV with a 10 Hz bandwidth and can accommodate even larger motion artifacts, up to 240 mV, with a 5 Hz bandwidth, demonstrating its robustness across various conditions and motion artifact ranges. The IC includes four analog front-end (AFE) channels, and they share the following programmable gain amplifier (PGA) and analog-to-digital converter (ADC) in a time-multiplexed manner. It supports a programmable gain from 20 dB to 54 dB. Furthermore, the chopper with an analog DC-servo loop (DSL) is added to cancel out electrode DC offsets (EDO) and achieve a low noise level by removing the 1/f noise. The proposed IC fabricated in a 0.18-μm CMOS technology process achieves an input-referred noise (IRN) of 0.71 μVrms over a bandwidth of 0.5 to 500 Hz and a signal-to-noise-and-distortion ratio (SNDR) of 63.34 dB. It consumes 5.74 μW of power and occupies an area of 0.40 mm² per channel. As a result, the proposed IC can record various biopotential signals thanks to its artifact-tolerant and low-noise characteristics.

In this paper, a wireless power transfer (WPT) system composed of a voltage-mode fully integrated resonance regulating rectifier (IR³) and an on-chip antenna running at 402 MHz has been designed for bioimplants in deep tissue. The proposed IR³, including a 200 pF decoupling capacitor, is implemented in a 0.22 mm² active area in the 180-nm CMOS process. A charging duration based regulation compensation circuit offers a low ripple factor of 0.3% at a 1.8 V output voltage and a high voltage conversion efficiency (VCE) of 1.73 to overcome the low inductive coupling coefficient (under 0.01) due to the deep implant scenario. And a clock gating VCDL-based on-&-off delay compensation scheme is proposed to compensate for the phase error of the IR³. Performing rectification and regulation simultaneously in a single stage, the IR³ effectively enhances power conversion efficiency. The whole system achieves a power conversion efficiency (PCE) of 65% with a 1.5 mW load. In addition, digital control-based compensation circuits also improve its transient response performance, the 1% setting time is only 6.9 μs when the load changes from 65 μW to 1.5 mW.

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 chipbased 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 customdesigned ODNP probes are used for proof-of-concept DNPenhanced NMR relaxometry and spectroscopy measurements. The presented chip-based ODNP platform achieves a maximum MW output power of 34dBm, resulting in a signal enhancement of -162 using the relaxometry ODNP probe with 1.4 μL of 10mM non-degassed TEMPOL solution, and an enhancement of -63 with the spectroscopy ODNP probe using 50 nL of the same solution. The proton polarization was increased from 0.5×10^-6 to 81×10^-6 at a low field of 0.16T. 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.

Photoplethysmogram (PPG) is widely used in wearable devices for health monitoring. High-precision signals are essential for medical diagnostics. However, motion artifacts in these devices can cause significant ambient light variation during PPG recording. This paper presents an accurate PPG recording front end with enhanced ambient light rejection (ALR). Quantization noise in a second-order sigma-delta modulator (SDM), used for direct current conversion, is reduced by extended counting of the modulator's residue. The first integrator of the SDM and the residue analog-to-digital converter (ADC) are reused in ALR circuits. The correlated double sampling (CDS) technique is enhanced by applying a first-order approximation of ambient light. Gain error in the residue ADC is reduced by charge compensation. The PPG front-end, implemented in a 180 nm process, achieves a dynamic range (DR) of 153.4 dB within a bandwidth of 20 Hz. The system operates with a minimum 1.28% duty cycle. Measurements of heart rate and blood oxygen at the fingertip and wrist verify the functionality of the PPG front end.