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. 2019 Jan 16;9(1):14.
doi: 10.3390/bios9010014.

Textile-Based Potentiometric Electrochemical pH Sensor for Wearable Applications

Libu Manjakkal  1 , Wenting Dang  2 , Nivasan Yogeswaran  3 , Ravinder Dahiya  4
Affiliations

Textile-Based Potentiometric Electrochemical pH Sensor for Wearable Applications

Libu Manjakkal et al. Biosensors (Basel). .

Abstract

In this work, we present a potentiometric pH sensor on textile substrate for wearable applications. The sensitive (thick film graphite composite) and reference electrodes (Ag/AgCl) are printed on cellulose-polyester blend cloth. An excellent adhesion between printed electrodes allow the textile-based sensor to be washed with a reliable pH response. The developed textile-based pH sensor works on the basis of electrochemical reaction, as observed through the potentiometric, cyclic voltammetry (100 mV/s) and electrochemical impedance spectroscopic (10 mHz to 1 MHz) analysis. The electrochemical double layer formation and the ionic exchanges of the sensitive electrode-pH solution interaction are observed through the electrochemical impedance spectroscopic analysis. Potentiometric analysis reveals that the fabricated textile-based sensor exhibits a sensitivity (slope factor) of 4 mV/pH with a response time of 5 s in the pH range 6⁻9. The presented sensor shows stable response with a potential of 47 ± 2 mV for long time (2000 s) even after it was washed in tap water. These results indicate that the sensor can be used for wearable applications.

Keywords: e-textile; graphite; pH sensor; potentiometric; wearable system.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) Schematic representation of flexible potentiometric pH sensor (SE-sensitive electrode and RE-reference electrode) on cloth. (b) The image of flexible and crumpled pH sensor (inset shows the image of the electrodes).
Figure 2
Figure 2
Scannng electron microscope (SEM) images: (a) top view of the sensitive electrode (SE) on cloth. (b) Surface morphology of the graphite sensitive electrode and (c) cross-sectional view of the layers of cloth, Ag electrode and graphite electrode.
Figure 3
Figure 3
(a) X-ray diffraction (XRD) spectrum of the film (b) surface profile scanning of the graphite-polyurethane (G-PU) composite film over an area of 5 × 5 mm2 (c) 3D surface image of the sensitive electrode for roughness measurement. (d) Morphological scan on surface roughness.
Figure 4
Figure 4
(a) Potential response of the sensor in pH buffer solution and (b) open circuit potential of the sensor with different pH value of solution.
Figure 5
Figure 5
Electrochemical reaction of cloth and G-PU electrode: (a) cyclic voltammetry (CV) analysis for pH 7, (b) Nyquist plot (inset shows the high frequency), and (c) Bode impedance plot of the SE at pH 7 with a frequency range of 10 mHz to 1 MHz.
Figure 6
Figure 6
(a) Potentiometric cloth-based sensor performance in deionized water after initial stabilization and after measuring in pH solution. (b) Response time of the sensor in pH solutions.
Figure 7
Figure 7
(a) CV analysis for pH 7.4, pH 7.4 with glucose and pH 7.4 with glucose and uric acid. (b) Open circuit potential (OCP) of the sensor in pH 7.4 and pH 7.4 with glucose and uric acid-based solution. (c) Impedance plot of the sensors (both SE and RE on cloth) at pH 7.4 based solution and inset shows the Nyquist plot.
Figure 8
Figure 8
Cyclic bending of textile-based pH sensor (a) resistance monitoring of pH sensor until the sensor was bent up to 500 times, (b) comparison in pH sensor’s resistance variation between the first and 500th bending cycle when it was bent with a bending radius of 11.39 mm.
See this image and copyright information in PMC

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