A Wearable and Multiplexed Electrochemical Sensor Suite for Real-Time Sweat Ionic Content and pH Monitoring With IoT Integration
Nafize Ishtiaque Hossain, Atul Sharma, Sameer Sonkusale
Abstract
Noninvasive sweat sensor integrated with electronic devices has great potential to monitor health conditions and diagnose several diseases in their early stages. In this letter, we present multiplexed flexible skin patches consisting of electrochemical sensors for monitoring potassium (K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ), calcium (Ca <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ), and pH levels in sweat with Internet-of-Things (IoT) connectivity. The sensor suite demonstrates dynamic and repeatable characteristics with a high degree of sensitivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\mathrm{S}}_{\mathrm{K}}^ + $</tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ = $</tex-math></inline-formula> 64.17 mV/dec., <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\mathrm{S}}_{\text{Ca}}^{2 + }$</tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ = $</tex-math></inline-formula> 38.33 mV/dec., and S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pH</sub> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ = \ - $</tex-math></inline-formula> 46.33 mV/dec.) and selectivity for the detection of desired ions. The sensor suite was tested for on-body during running exercise for over 60 min; results show an increasing trend in K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> and pH levels and decreasing trend of Ca <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> levels in real sweat, as expected. The developed device can be a pivotal tool for point-of-care applications for in-field sweat ionic content and pH analysis.