Partha Sarati Das

Fashionable wrist band using highly conductive fabric for electrocardiogram signal monitoring

In this paper, a flexible and wearable fabric-based and highly conductive wrist band with portable electrocardiogram (ECG) equipment is presented for the long-term monitoring of ECG signals. The impedance properties, skin irritation, and sensitivity are then investigated using the proposed wrist band. The wrist band was constructed using conductive fabric, a Velcro strap, a metal snap, and a nickel connector. The entire polyester fabric surface was coated with nickel, copper, and gold. The sheet resistance of the conductive fabric is 0.06 Ω/sq. It is appropriate to use a dry fabric electrode for long-term monitoring purposes, rather than a gel-based Ag/AgCl electrode. The proposed system does not require additional active electrodes, and a single-layer standard printed circuit board (PCB) was developed to allow for portable ECG signal acquisition. We measured the impedance as per the frequency change and compared the outcomes with those of Ag/AgCl electrodes. Subsequently, we measured the ECG signal and investigated the possible artifacts caused by motion. The skin-electrode impedance of the wrist band was measured and compared to the Ag/AgCl electrodes, where we found a lower impedance for the wrist band electrodes. In addition, the power spectrum of the biopotential signals obtained from the wrist band electrodes are evaluated and compared to those obtained with Ag/AgCl electrodes for estimating signal quality. The experimental results show that the proposed electrode can successfully acquire an ECG signal from the wrist when the subject is resting and fewer motion artifacts are shown when the subject moves, rendering the proposed electrode comparable with the traditional disposable and gelled Ag/AgCl electrodes.

A highly stretchable and conductive 3D porous graphene metal nanocomposite based electrochemical-physiological hybrid biosensor

Recently, highly stretchable and flexible electrodes essential for wearable electronic devices has been reported. However, their electrical resistances are high, the fabrication processes are complicated and involve a high cost, and deformations such as stretching can lead to the degradation on electrical performance. To address these issues, a novel fabrication process (both inexpensive and simple) for the highly stretchable and conductive electrodes using well patterned 3D porous laser-induced graphene silver nanocomposite was developed. The fabricated electrode exhibited a high, uniform electrical conductivity even under mechanical deformations. Addition of platinum and gold nanoparticles (PtAuNP) on the 3D porous LIG greatly improved the electrochemical performance for wearable glucose sensor applications. The fabricated glucose sensor exhibited low detection limit (5 µM), and acceptable detection range from 0 to 1.1 mM (covers the glucose range in sweat), and high linearity (0.99). In addition, the fabricated pH sensor also exhibited a linear response (66 mV/pH) at the range from 4 to 7. This work successfully demonstrates the potential of this novel fabrication technique and stretchable LIG metal nanocomposite for wearable electrochemical-physiological hybrid biosensors.

A Flexible Capacitive Pressure Sensor for Wearable Respiration Monitoring System

This paper presents the design, fabrication, and characterization of a wearable capacitive pressure sensor for respiration-monitoring systems. For the dielectric layer of the proposed capacitive sensor, Porous Ecoflex with a porosity of ~36% was prepared from a manually made sugar cube via a simple melting process. A polydimethylsiloxane-based silver nanowire and carbon fibers thin films were used for the sensor electrodes. The fabricated flexible pressure sensor exhibited a high sensitivity of 0.161 kPa−1 for low pressure regime (<10 kPa), a wide working pressure range of <200 kPa, and a high durability over 6000 cycles. Since the proposed sensor is flexible and resizable, it can be integrated into clothes and easily placed at any location of the human body. Finally, the practicality of the sensor was successfully demonstrated by integrating the sensor into a waist belt to monitor the real-time respiration signal of the human being. The finding is highly useful to monitor respiration signal for the detection of diseases, such as sleep apnea, asthma, and others.