Abstract

Degradation of ECG electrodes critically impacts the reliability of long-term cardiac monitoring. Existing systems typically fail to detect electrode deterioration until signal quality has already degraded. This paper presents an impedance-based electrode quality assessment system that operates along with ECG system. The system estimates the electrode time constant (τ) using RC decay analysis and jointly evaluates τ and interface capacitance (Cint) to identify electrode degradation. Commercial Ag/AgCl electrodes were evaluated under simulated thermal, saline, and mechanical stress conditions. Baseline parameters for the device under test (DUT), obtained by averaging measure- ments over 56,000 excitation cycles per minute, were τ0 = 0.103± 0.018 ms and Cint,0 = 57.27 nF, while degraded state values reached τmax = 1.151 ± 0.112 ms and Cint,max = 2071.33 nF. A degradation threshold of τ > 0.206 ms (corresponding to > 5σ above the baseline) was established to generate a warning to the user. Implemented on an ESP32-C3, the system consumes 7.7 mW and provides a low-cost, real-time method for monitoring electrode health. The proposed scheme is readily adaptable to a wide range of physiological sensing systems.

Abstract

The paper details a system-level design of a nanosecond-range pulsed laser diode driver with adjustable current and high pulse repetition rate, optimised for low-power laser diodes. The design incorporates the summing of two independently adjustable constant current sources, one provides DC bias, while the second one produces current pulses (via externally modulated GaN FET). The circuit is simulated in LTspice with two laser diode SPICE models, and simulation results are analysed to evaluate system performance and stability.

Abstract

Wearable heating pads are widely used as therapeutic warmers for tending to multiple health conditions. Precise temperature control is the key to ensuring the safety and effectiveness of the device due to its near-skin application. The paper presents a comparative analysis of temperature control using Proportional-Integral (PI) and Proportional-Integral-Derivative(PID) controllers based on time domain response parameters. The system utilizes an Arduino microcontroller to perform the error calculation between the set point and real-time temperature and accordingly generate PWM pulses to control the actuator driving the heating pad. The device features three different modes of operation based on the analog output voltage from an external driving circuit. Alongside, characterization data, system design and implementation of controllers, a comparative time domain response parameter analysis based on experimental data is also presented.

Abstract

Detection and continuous monitoring of iron in
drinking water is essential for testing potability, environmental pollution and contamination. Many conventional methods are either too costly, bulky with limited accuracy and slow. In this paper, we present the design, fabrication and testing of a low- cost, portable electrochemical sensor for detecting iron content
in water. We test by driving reaction using a reagent and change in reaction potential is observed using potentiostat. After this, we back calculated to find the shift in ferrous ion concentration upon the reagent's addition.

Abstract

The paper describes a platform for quick characterization of photodiodes exploring low reverse bias performance for various sensing applications. We demonstrated the method on a widely used photodiode, BPW34. An Arduino-based automated system is utilized to sweep biasing voltages and record photocurrent responses using a sense resistor. The BPW34 photodiode shows a higher response for red LASER light, with a photocurrent of around 260 μA. Various light sources are also tested and the results are reported. These results are analyzed and interpreted with context to the existing literature.

Abstract

This paper presents the design and development of heater control for a flexible embedded microheater (7000 um x 9000 um) for a lab-on-a-chip system. Our work focuses on advancing the PWM-based control system with the goal of reducing the system time constant. We also present the fabrication of an embedded flexible microheater in a PDMS substrate. We validate the efficacy of the flexible microheater and its control system by using it for glucose detection. A steady state temperature in the range of 40$^o$C to 120 degree C is achieved in approximately 40 s, with the heater's power consumption ranging from 0.4 W to 2 W. The novelty of the work lies in that we have made a small, flexible, low-cost chip without the use of sophisticated equipment or conventional fabrication techniques.

Abstract

Single photon avalanche diode (SPAD) plays a vital role in low-light imaging. Process libraries do not have a SPAD device model for simulation. A circuit model that can accurately simulate SPAD's behavior is required. This paper reviews and compares currently available SPAD models. A passive quenching circuit (PQC) is used to characterize SPAD models. 30 µm X 30 µm square-shaped n+/p-sub, nwell/p-sub, p+/nwell/p-sub SPADs without guard rings are designed, and a breakdown voltage of 11.16, 14.78, and 10.22 volts is observed, respectively. The models are compared with SPAD's quenching and recharge time. The n+/p-sub SPAD is used for our study. From this work, we conclude that the most accurate modeling of SPAD can be done by an equation-based model. We also compare the photon detection efficiency (PDE) and dark count rates (DCR). This study is conducted in the TSMC 180 nm process.

Abstract

This paper presents the implementation of inexpensive and adaptable micro-heater circuits utilizing the principles of joule heating and induction heating. The heating mechanisms were simulated and analyzed using COMSOL Multiphysics software. A comparative investigation was conducted in simulation to examine the performance of both heating techniques, and findings are reported. Furthermore, a flexible device prototype was fabricated to demonstrate the feasibility of the micro-heater, and a comparative experimental analysis was performed on micro-heaters integrated in two distinct substrates, namely polydimethylsiloxane (PDMS) and Ecoflex.

Abstract

Efficient and reliable non-invasive methods for micro-organism detection have significant implications in various fields such as medical diagnostics, environmental monitoring, and food safety. Existing detection techniques, such as culture-based methods, polymerase chain reaction (PCR) have limitations including time-consuming processes, expensive equipment requirements and invasive sampling procedures. These drawbacks emphasize the need for alternate detection techniques that are non-invasive, rapid, sensitive, specific, and user-friendly. For this purpose, in this research, we present a portable integrated system for micro-organism detection, which is based on electrochemical impedance spectroscopy (EIS). The proposed system includes Zinc Oxide (ZnO) nanorods based interdigitized electrode (IDE) sensor and an EIS circuit. This work also presents the considerations and methodology for the fabrication of ZnO nanorods with high-yield. To validate the efficacy of the proposed methods, experimental results through scanning electron microscope are also presented. Finally, measurement results for detection of a micro-organism (yeast) is also presented to demonstrate the utility and effectiveness of the proposed methods and system.

Abstract

This paper presents a custom design and analysis of a CMOS-compatible, color-segregating photodiode design for Lab-on-a-Chip applications. The design is based on minimal post-processing of a CMOS photodiode circuit to achieve improved segregation of red, green, and blue wavelengths. Lower wavelengths are blocked by depositing blocking materials (polysilicon, silicon nitride) of different thicknesses. Diodes compatible with the process are used for collecting the electron-hole pairs. We have used the 180 nm TSMC process for our design and analysis, but it is applicable to other processes as well.