Effects of Fabrication Techniques and Durability Performance on Resistance of Fibre-based PEDOT:PSS/GO pH Sweat Sensor

Abstract

Most wearable electronics widely incorporate metal electrodes for parameter detection but these electrodes possess drawbacks due to corrosion and performance degradation. Therefore, in this work, pH sweat sensor is fabricated by using highly conductive, stable and non-toxic PEDOT:PSS/GO nanocomposite on flexible cotton fibre substrate. This work is aimed to determine the effects of fabrication techniques and durability performance on pH sensitivity of fibre-based PEDOT:PSS/GO sensor via resistance measurements. In this work, a wearable fibre-based sensor is developed by using Poly (3,4 ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT:PSS), and Graphene Oxide (GO) nanocomposite. Sample characterisations are completed by analysing absorbance spectrums, FESEM images and XRD spectra. One layer PEDOT:PSS/GO of 4:2 ratio is fabricated on cotton fabric by using dip coating and screen-printing techniques. Lower resistance of 105 Ω and higher conductivity are achieved by using dip coating technique compared to screen printing, as better absorption of nanocomposite into fiber strands via this method, leads to excellent charge distribution on coated fabric. Resistance increases proportionally with pH values. Resistance of 1.547 kΩ, 3.791 kΩ and 9.18 kΩ are measured for pH 4.00, 6.86 and 9.18 respectively. Nanocomposite layer fabricated with dip coating is also stable, durable and remained intact on the coated fabric after soaking test in distilled (DI) water for 45 minutes. On the other hand, resistance values are 3.11 Ω, 4.81 Ω and 6.54 Ω when the sensor bends at 30°, 60° and 90° respectively. This is due to additional introduced strain and redistribution of charges on the fabric after repeated movements. Based on excellent chemiresistive response towards sweat pH detection, several health conditions such as hyperhidrosis, normal state and cystic fibrosis associated with sweat pH of 4.00, 6.86 and 9.18 respectively, could be possibly identified. These promising results open up possibilities for future studies in the development of nanocomposite-based health monitoring wearable devices.