Impedance-Readout Integrated Circuits for Electrical Impedance Spectroscopy: Methodological Review.

This review article provides a comprehensive overview of impedance-readout integrated circuits (ICs) for electrical impedance spectroscopy (EIS) applications. The readout IC, a crucial component of on-chip EIS systems, significantly affects key performance metrics of the entire system, such as frequency range, power consumption, accuracy, detection range, and throughput. With the growing demand for portable, wearable, and implantable EIS systems in the Internet-of-Things (IoT) era, achieving high energy efficiency while maintaining a wide frequency range, high accuracy, wide dynamic range, and high throughput has become a focus of research.

A Wireless and Wearable Body-Pressure-Monitoring System for the Prevention of Pressure-Induced Skin Injuries.

This article presents a wireless and wearable body-pressure-monitoring system for the on-site, real-time prevention of pressure injuries for immobilized patients. For the prevention of pressure-induced skin injuries, a wearable pressure sensor system is designed to monitor the pressure at multiple sites on the skin and to alert the danger of prolonged application of pressure on the skin with a pressure-time integral (PTI) algorithm. The wearable sensor unit is developed using a pressure sensor based on a liquid metal microchannel and integrated with a flexible printed circuit board that includes a thermistor-type temperature sensor.

Wireless Kitchen Fire Prevention System Using Electrochemical Carbon Dioxide Gas Sensor for Smart Home.

This paper presents a wireless kitchen fire prevention system that can detect and notify the fire risk caused by gas stoves. The proposed system consists of two modules. The sensor module detects the concentration of carbon dioxide (CO2) near the gas stove and transmits the monitoring results wirelessly.

On-Chip Sinusoidal Signal Generators for Electrical Impedance Spectroscopy: Methodological Review.

This paper reviews architectures and circuit implementations of on-chip sinusoidal signal generators (SSGs) for electrical impedance spectroscopy (EIS) applications. In recent years, there have been increasing interests in on-chip EIS systems, which measure a target material's impedance spectrum over a frequency range. The on-chip implementation allows EIS systems to have low power and small form factor, enabling various biomedical applications.

An Impedance Readout IC with Ratio-Based Measurement Techniques for Electrical Impedance Spectroscopy.

This paper presents an error-tolerant and power-efficient impedance measurement scheme for bioimpedance acquisition. The proposed architecture measures the magnitude and the real part of the target complex impedance, unlike other impedance measurement architectures measuring either the real/imaginary components or the magnitude and phase. The phase information of the target impedance is obtained by using the ratio between the magnitude and the real components.

A Polar-Demodulation-Based Impedance-Measurement IC Using Frequency-Shift Technique With Low Power Consumption and Wide Frequency Range.

In this paper, we present a new impedance measurement integrated circuit (IC) for achieving a wideband coverage up to 10 MHz and low power consumption. A frequency-shift technique is applied to down-shift the input frequency, which ranges from 100 kHz to 10 MHz, into an intermediate frequency of 10 kHz, while the frequency-shifting is bypassed when the input frequency falls in the range from 100 Hz to 100 kHz. It results in 100 times relaxation of the requirement on the instrumentation amplifier (IA) bandwidth and the comparator delay, greatly reducing overall power consumption.

A Scalable Readout IC Based on Wideband Noise Cancelling for Full-Rate Scanning of High-Density Microelectrode Arrays.

This paper presents a highly scalable readout IC for high-density microelectrode arrays (MEAs). Although the recent development of large-scale high-density MEAs provides opportunities to achieve sub-cellular neural recording over a wide network area, it is challenging to implement the readout IC that can operate with such MEAs. The requirement of high-speed recording in large-scale arrays induces wideband-noise folding, which makes it challenging to achieve a good noise performance for high-fidelity neural recording.

A Power-Efficient Radiation Sensor Interface with a Peak-Triggered Sampling Scheme for Mobile Dosimeters.

Radiation sensor interfaces for battery-powered mobile dosimeters must consume low power to monitor the amount of radiation exposure over a long period. This paper proposes a power-efficient radiation sensor interface using a peak-triggered sampling scheme. Since the peak of the analog-to-digital converter's (ADC's) input represents radiation energy, our ADC only operates around the peak value thanks to the proposed sampling scheme.

Design of Reconfigurable Time-to-Digital Converter Based on Cascaded Time Interpolators for Electrical Impedance Spectroscopy.

This paper presents a reconfigurable time-to-digital converter (TDC) used to quantize the phase of the impedance in electrical impedance spectroscopy (EIS). The TDC in the EIS system must handle a wide input-time range for analysis in the low-frequency range and have a high resolution for analysis in the high-frequency range. The proposed TDC adopts a coarse counter to support a wide input-time range and cascaded time interpolators to improve the time resolution in the high-frequency analysis without increasing the counting clock speed.

Isolation and identification of a sibutramine analogue adulterated in slimming dietary supplements.

A suspected sibutramine analogue was detected in a slimming functional food by an ultra performance liquid chromatography-electrospray ionisation-time of flight mass spectrometry (UPLC-ESI-TOF/MS) method. The ultraviolet (UV) spectrum of this suspected compound showed close similarity to that of sibutramine. The sample was extracted with 70% MeOH and isolated by semi-preparative column chromatography.