Fabrication of a Wearable Flexible Sweat pH Sensor Based on SERS-Active Au/TPU Electrospun Nanofibers

Michael Chung, William H Skinner, Colin Robert, Colin J Campbell, René M Rossi, Vasileios Koutsos, Norbert Radacsi

Research output: Contribution to journalArticlepeer-review

Abstract

Development of wearable sensing platforms is essential for the advancement of continuous health monitoring and point-of-care testing. Eccrine sweat pH is an analyte that can be noninvasively measured and used to diagnose and aid in monitoring a wide range of physiological conditions. Surface-enhanced Raman scattering (SERS) offers a rapid, optical technique for fingerprinting of biomarkers present in sweat. In this paper, a mechanically flexible, nanofibrous, SERS-active substrate was fabricated by a combination of electrospinning of thermoplastic polyurethane (TPU) and Au sputter coating. This substrate was then investigated for suitability toward wearable sweat pH sensing after functionalization with two commonly used pH-responsive molecules, 4-mercaptobenzoic acid (4-MBA), and 4-mercaptopyridine (4-MPy). The developed SERS pH sensor was found to have good resolution (0.14 pH units for 4-MBA; 0.51 pH units for 4-MPy), with only 1 μL of sweat required for a measurement, and displayed no statistically significant difference in performance after 35 days (p = 0.361). Additionally, the Au/TPU nanofibrous SERS pH sensors showed fast sweat-absorbing ability as well as good repeatability and reversibility. The proposed methodology offers a facile route for the fabrication of SERS substrates which could also be used to measure a wide range of health biomarkers beyond sweat pH.

Original languageEnglish
Pages (from-to)51504–51518
JournalACS Applied Materials & Interfaces
Volume13
Issue number43
Early online date21 Oct 2021
DOIs
Publication statusPublished - 3 Nov 2021

Keywords

  • pH sensor
  • Surface Enhanced Raman Spectroscopy (SERS)
  • electrospinning
  • sweat sensing
  • wearable

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