Dual-valved skin-interfaced microfluidic device for programmed time-control sweat collection

Biomarkers in human sweat can provide valuable insights into physiological states, identify diseases, and help clinicians understand patients without invasive measurements. However, obtaining accurate long-term data from sweat using current sweat collection methodology raises doubts. Here, we describe a soft-bioelectronic platform that uses a thermal expansion valve to collect sweat under programmed time control. By incorporating expandable microspheres, the skin-interfaced microfluidic device platform merges capillary burst valves and irreversible-thermal expansion valves. An expansion layer below the microfluidic channels expands irreversibly upon heat delivery from underlying microheaters. The thermal expansion valve isolates the collected sweat into separate chambers to minimize internal mixing. The human study demonstrates that our novel time-programmed sweat collection device improved sweat analyte data (sweat volume, pH, lactate, and cortisol) from the conventional sweat collection. In addition, the human study results indicate a correlation between sweat rate and sweat lactate with aerobic and anaerobic exercises. Our approach can be integrated with past and current microfluidic systems and other chemical sensing modalities, such as colorimetric and electrochemical measurements of sweat analytes present in current sweat devices for advanced on-board diagnostics.