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

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.

Abstract

In this paper, we present the design of a complete system for recording electrophysiology signals from patients and also present the recordings. We observe the signals from relaxed and fatigued muscles as well as from heart (ECG) signals. We designed the complete integrated circuit for flexible substrates using basic ICs. The system captures, amplifies, and filters using analog circuits. The instrumentation amplifier (AD623) in the first step amplifies (gain = 100), a combination of Bessel low- pass filter (2nd-order active low-pass filter with LM741 op-amp in Sallen-Key topology) cut-off = 500 Hz, HPF (1st-order active high-pass filter with LM741) cut-off = 0.03, and twin-T active Notch filter with LM741 filters the input. Design, analysis, and data from the prototype and packing (flexible) plan for this customized new system are presented in this paper. Index Terms—Electromyography, Instrumentation amplifier, Wearable Systems, Bio instrumentation, Analog circuit design, Second order filters

Abstract

This paper presents a low cost, easy to fabricate, thin-film sensor. We used three different methods to make the thin film using two different base (film) materials: carbon and graphite. We briefly summarize the method and outcome of multi-layer thin film fabrication using spray coating, spin-coating, and drop-casting. The quality of the thin films is compared, and electrical resistance is characterized. The fabricated thin film is used to measure humidity and is characterized against a commercial humidity sensor (DHT22). The experimental details and results of humidity measurement are discussed. We were able to achieve resistance range of 5k - 1.5k ohms for 40 - 80 % RH, respectively. Plans to further optimize the sensitivity of the sensor, in future is discussed. Index Terms—thin film sensors, spray coating, spin-coating, drop-casting, low-cost sensor fabrication, humidity sensor

Abstract

Research and fabrication of micro devices hold the key to low power devices, sensors and lab-on-a-chip systems which are in much need today for diagnosis, IOT etc. Cost of setting up a fabrication laboratory and conducting photolithography is high due to need of expensive equipment. We present a design of low-cost UV exposure system which can be used for both high resolution and low resolution photolithography. In first part, we present the study of irradiance distribution patterns of different UV LED arrangements. We use uniformity as a criterion for selecting the arrangement that gives the best illumination uniformity in largest area. The maximum, minimum and average exposure energy and uniformity have been presented. Using these results, we present an optimal system design for UV photolithography. The novelty of our work is simulating the UV exposure system for different parameters for making an optimal choice for a versatile system (high energy & low energy), different uniformity for different resolution to save power and have better control.