Solvent Treatment of Wet-Spun PEDOT: PSS Fibers for Fiber-Based Wearable pH Sensing

Abstract

There is a growing desire for wearable sensors in health applications. Fibers are inherently flexible and as such can be used as the electrodes of flexible sensors. Fiber-based electrodes are an ideal format to allow incorporation into fabrics and clothing and for use in wearable devices. Electrically conducting fibers were produced from a dispersion of poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT: PSS). Fibers were wet spun from two PEDOT: PSS sources, in three fiber diameters. The effect of three different chemical treatments on the fibers were investigated and compared. Short 5 min treatment times with dimethyl sulfoxide (DMSO) on 20 μm fibers produced from Clevios PH1000 were found to produce the best overall treatment. Up to a six-fold increase in electrical conductivity was achieved, reaching 800 S cm−1, with no loss of mechanical strength (150 MPa). With a pH-sensitive polyaniline coating, these fibers displayed a Nernstian response across a pH range of 3.0 to 7.0, which covers the physiologically critical pH range for skin. These results provide opportunities for future wearable, fiber-based sensors including real-time, on-body pH sensing to monitor skin disease.

Flexible Sensors Based on Conductive Polymers

“…Different treatments of the polymeric fibers with DMSO, sulfuric acid and formic acid were analyzed. The optimal balance of electrical conductivity and mechanical strength for a pH sensor was found for the fibers treated with DMSO [164]. Kim et al [165] fabricated a microfiber-based substrate-free organic electrochemical transistor by wet-spinning (OECTs).…”

Textile Chemical Sensors Based on Conductive Polymers for the Analysis of Sweat

“…Among CPs, polyaniline (PANI) stands out as the most prominent example of non-redox doping caused by acid/base equilibria between deprotonated (e.g., base, dedoped) and protonated (e.g., salt, doped) forms and has been exploited for the design of textile potentiometric sensors. In particular, PANI electropolymerization has been carried out on wet-spun PEDOT:PSS fibers [ 80 ] and elastomeric gold fibers woven into a textile matrix [ 81 ] ( Figure 4 A), both showing good resiliency of the sensing performance during stretchability tests. In the first case, treatment with the organic solvent dimethyl sulfoxide (DMSO) increased the conductivity of the PEDOT:PSS fiber, thus facilitating PANI electrodeposition, and the sensor response covered the pH range 3.0–7.0 with Nernstian sensitivity (−56 ± 7 mV.pH −1 ).…”

Printed pH Sensors for Textile‐Based Wearables: A Conceptual and Experimental Study on Materials, Deposition Technology, and Sensing Principles

“…[50][51][52][53] PEDOT:PSS is applied to develop pH sensors, which are described in different research works. [46,[54][55][56] pH sensing is realized by noting the conductivity changes of the PEDOT:PSS layer. [57][58][59] In recent times, organic compounds are increasingly being used in biosensors.…”