Abstract
In sport, exercise and healthcare settings, there is a need for continuous, non-invasive monitoring of biomarkers to assess human performance, health and wellbeing. Here we report the development of a flexible microfluidic platform with fully integrated sensing for on-body testing of human sweat. The system can simultaneously and selectively measure metabolite (e.g. lactate) and electrolytes (e.g. pH, sodium) together with temperature sensing for internal calibration. The construction of the platform is designed such that continuous flow of sweat can pass through an array of flexible microneedle type of sensors (50µm diameter) incorporated in a microfluidic channel. Potentiometric sodium ion sensors were developed using a polyvinyl chloride (PVC) functional membrane deposited on an electrochemically deposited internal layer of Poly(3,4-ethylenedioxythiophene) (PEDOT) polymer. The pH sensing layer is based on a highly sensitive membrane of iridium oxide (IrOx). The amperometric-based lactate sensor consists of doped enzymes deposited on top of a semipermeable copolymer membrane and outer polyurethane layers. Real-time data were collected from human subjects during cycle ergometry and treadmill running. A detailed comparison of sodium, lactate and cortisol from saliva is reported, demonstrating the potential of the multi-sensing platform for tracking these outcomes. In summary, a fully integrated sensor for continuous, simultaneous and selective measurement of sweat metabolites, electrolytes and temperature was achieved using a flexible microfluidic platform. This system can also transmit information wirelessly for ease of collection and storage, with the potential for real-time data analytics.
Highlights
One of the unique challenges in sport, exercise science and healthcare, is the need for continuous, non-invasive monitoring of biomarkers for assessing human performance, health and wellbeing
We present the development of a wearable electronic sensor, complete with microfluidic sampling and wireless readout electronics, which simultaneously measures the concentrations of hydrogen and sodium ions, as well as lactate in human sweat
We carried out independent validation of the pH sensor for sweat monitoring during the exercise testing of human subjects (Figure 2) against spot measurements taken with a commercial pH sensor (Hanna)
Summary
One of the unique challenges in sport, exercise science and healthcare, is the need for continuous, non-invasive monitoring of biomarkers for assessing human performance, health and wellbeing The monitoring of hydration status and other vital signs during sporting activities can provide a wealth of information regarding one’s physiological capacity and efficiency under stress. It may assist in personalising programmes for optimal training gins and recovery. Sweat has been recognised as an accessible bodily fluid that can provide important diagnostic information (Mena-Bravo and de Castro 2014; Raiszadeh et al 2012). Hypotonic and odourless fluid often described as an ultrafiltrate of plasma It contains mainly ions such as sodium, potassium, calcium, magnesium, chloride and lactate. With a typical sweat rate of human males measuring 0.85 mg cm-2 min-1 at the lower back (Patterson et al 2000)
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