Wearable monitoring systems provide valuable insights about the state of wellness, performance, and progression of diseases. Although conventional wearable systems have been effective in measuring a few key biophysical markers, they offer limited insights into biochemical activity and are otherwise cumbersome in ambulatory modes of use, relying on wired connections, mechanical straps, and bulky electronics. Recent advances in skin‐interfaced microfluidics, stretchable/flexible electronics, and mechanics have created new wearable systems with capabilities in real‐time, noninvasive analysis of sweat biochemistry in combination with biophysical metrics. Here, the latest technologies in multifunctional sweat sensing systems are presented with a focus on novel microfluidic designs, fully‐integrated wireless electrochemical sensors, and hybrid biochemical/biophysical sensing capabilities, creating real‐time physiological insights.
Comprehensive analysis of sweat chemistry provides noninvasive health monitoring capabilities that complement established biophysical measurements such as heart rate, blood oxygenation, and body temperature. Recent developments in skin‐integrated soft microfluidic systems address many challenges associated with standard technologies in sweat collection and analysis. However, recording of time‐dependent variations in sweat composition requires bulky electronic systems and power sources, thereby constraining form factor, cost, and modes of use. Here, presented are unconventional design concepts, materials, and device operation principles that address this challenge. Flexible galvanic cells embedded within skin‐interfaced microfluidics with passive valves serve as sweat‐activated “stopwatches” that record temporal information associated with collection of discrete microliter volumes of sweat. The result allows for precise measurements of dynamic sweat composition fluctuations using in situ or ex situ analytical techniques. Integrated electronics based on near‐field communication (NFC) protocols or docking stations equipped with standard electronic measurement tools provide means for extracting digital timing results from the stopwatches. Human subject studies of time‐stamped sweat samples by in situ colorimetric methods and ex situ techniques based on inductively coupled plasma mass spectroscopy (ICP‐MS) and chlorodimetry illustrate the ability to quantitatively capture time‐dynamic sweat chemistry in scenarios compatible with field use.
Important insights into human health can be obtained through the non-invasive collection and detailed analysis of sweat, a biofluid that contains a wide range of essential biomarkers. Skin-interfaced microfluidic platforms,...
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