Wireless Multimodality Sensing System-on-a-Chip With Time-Based Resolution Scaling Technique and Analog Waveform Generator in 0.18 µm CMOS for Chronic Wound Care.

Multimodal sensing can provide a comprehensive and accurate diagnosis of biological information. This paper presents a fully integrated wireless multimodal sensing chip with voltammetric electrochemical sensing at a scanning rate range of 0.08-400 V/s, temperature monitoring, and bi-phasic electrical stimulation for wound healing progress monitoring. The time-based readout circuitry can achieve a 1-20X scalable resolution through dynamic threshold voltage adjustment. A low-noise analog waveform generator is designed using current reducer techniques to eliminate the large passive components. The chip is fabricated via a 0.18 µm CMOS process. The design achieves R2 linearity of 0.995 over a wide current detection range (2 pA-12 µA) while consuming 49 µW at 1.2 V supply. The temperature sensing circuit achieves a 43 mK resolution from 20 to 80 degrees. The current stimulator provides an output current ranging from 8 µA to 1 mA in an impedance range of up to 3 kΩ. A wakeup receiver with data correlators is used to control the operation modes. The sensing data are wirelessly transmitted to the external readers. The proposed sensing IC is verified for measuring critical biomarkers, including C-reactive protein, uric acid, and temperature.

A 19 µW, 50 kS/s, 0.008-400 V/s Cyclic Voltammetry Readout Interface With a Current Feedback Loop and On-Chip Pattern Generation.

A cyclic voltammetry electrochemical sensing chip was implemented with a time-based readout circuit and a current feedback control loop for wide-range and high-linearity current detection. The design utilizes a chopper-stabilized, low-noise potentiostat circuit and a delay chain time-to-digital converter to improve accuracy and the conversion rate. A current feedback loop is employed to mitigate nonlinearity of the current-to-frequency converter. Also, an on-chip pattern generator with a current reducer is used to create area-efficient, multi-rate ramp signals for cyclic voltammetry and fast-scan cyclic voltammetry measurements. The chip is fabricated using a 0.18-µm CMOS process. It achieves an 8-nA current resolution in the current range of -7 µA to 10 µA with an R2 linearity of 0.999 while consuming 19 µW. The Allan deviation floor is 4.83 Hz at the 7-second integration window, resulting in an 87-pArms input-referred current noise. The applicable limit of detection for K3[Fe(CN)6] concentration is 31 pM. To measure various reactions, the scan rate can be adjusted from 0.008 V/s to 400 V/s with a throughput data rate of up to 50 kS/s.

A Two-Electrode, Double-Pulsed Sensor Readout Circuit for Cardiac Troponin I Measurement.

This paper presents a pulse-stimulus sensor readout circuit for use in cardiovascular disease examinations. The sensor is based on a gold nanoparticle plate with an antibody post-modification. The proposed system utilizes gated pulses to detect the biomarker Cardiac Troponin I in an ionic solution. The characteristic of the electrostatic double-layer capacitor generated by the analyte is related to the concentration of Cardiac Troponin I in the solvent. After sensing by the transistor, a current-to-frequency converter (I-to-F) and delay-line-based time-to-digital converter (TDC) convert the information into a series of digital codes for further analysis. The design is fabricated in a 0.18-µm standard CMOS process. The chip occupies an area of 0.92 mm2 and consumes 125 µW. In the measurements, the proposed circuit achieved a 1.77 Hz/pg-mL sensitivity and 72.43 dB dynamic range.

A Microwatt Dual-Mode Electrochemical Sensing Current Readout With Current-Reducer Ramp Waveform Generation.

An electrochemical sensing chip with an integrated current-reducer pattern generator and a current-mirror based low-noise chopper-stabilization potentiostat circuit is presented. The pattern generator, utilizing the current reducer technique and pseudo resistors, creates a sub-Hz ramp signal for the cyclic voltammetric (CV) measurement without large-size passive components. The proposed design adopts the chopper-stabilization and low-noise biasing technique for the potentiostat and a counter-based time-to-digital converter to reduce the amplitude noise effects and to convert the sensing current signal to digital codes for further data processing. The design is fabricated using a 0.18-µm CMOS process and achieves a 41 pA current resolution in the current range of ±5 µA while maintaining the R2 linearity of 0.998. The system consumes 16 µW from a 1.2 V supply when a 5 µA sensing current is detected. The power efficiency of the readout interface is 0.31, and the sensing current dynamic range is 108 dB. The design is fully integrated into a single chip and is successfully tested in the dual-mode (CA/CV) measurements with commercial gold electrodes in a potassium ferricyanide solution in sub-millimolar concentrations.

Design and Study of a Portable High-frequency Ventilator for Clinical Applications.

Treatment costs for ventilator-dependent patients are a substantial burden not only for their family but also for medical systems in general. Recently, using high-frequency ventilators have been shown to reduce the risk of lung injury through low-volume airflow. However, the machines used today remain bulky, costly, and only for use in hospital settings. To provide intermediate therapy for patients between hospitalization and complete discharge, a portable, light-weight high-frequency ventilator is an urgent need. This work presents the design of a portable high-frequency ventilator and a study of its practicality for further clinical medical applications. Through the integration of advanced electronics and mechanical instruments, we develop a portable high-frequency ventilator with reconfigurable oxygen flow rate, applied pressure, and air volume for the needs of individual patients. A miniaturized portable high-frequency ventilator with digital controller and feedback system for stabilization and precision control is implemented. The efficiency of CO2 washout using the proposed ventilator has been demonstrated in animal trials.

A Reconfigurable, Pulse-shaping Potentiometric Readout System for Bio-Sensing Transistors.

This paper presents a new multi-modality readout system for potentiometric electrochemical sensors. The design adopts a pulse modulation at the gate and drain of the Bio-FET sensors to reduce the effects of charge accumulation between the surface of the electrodes and the ion analytes. The adjustable duration and amplitude of stimuli signals provide flexibility for different biosensing applications and a wide range of detectable concentration. Also, an oscillator-based architecture is proposed for digitization and integration. The counting time can be adjusted to enhance the resolution of the readout system. The proposed potentiometric sensing system was tested with 0.1-10 mM Potassium Ferricyanide (K3[Fe(CN)6]), and the results are interpreted in the micro-LCD on the board. The design offers the opportunity for a handheld medical device with fast and real-time monitoring of biomarkers and ion analytes.