Battery-free, skin-interfaced microfluidic/electronic systems for simultaneous electrochemical, colorimetric, and volumetric analysis of sweat

Bandodkar, A. J.*; Gutruf, P.*; Choi, J.*; Lee, K.-H.*; Sekine, Yurina   ; Reeder, J. T.*; Jeang, W. J.*; Aranyosi, A. J.*; Lee, S. P.*; Model, J. B.*; Ghaffari, R.*; Su, C.-J.*; Leshock, J. P.*; Ray, T.*; Verrillo, A.*; Thomas, K.*; Krishnamurthi, V.*; Han, S.*; Kim, J.*; Krishnan, S.*; Hang, T.*; Rogers, J. A.*

Interest in advanced wearable technologies increasingly extends beyond systems for biophysical measurements to those that enable continuous, non-invasive monitoring of biochemical markers in biofluids. Here, we introduce battery-free, wireless microelectronic platforms that perform sensing via schemes inspired by the operation of biofuel cells. Combining these systems in a magnetically releasable manner with chrono-sampling microfluidic networks that incorporate assays based on colorimetric sensing yields thin, flexible, lightweight, skin-interfaced technologies with broad functionality in sweat analysis. A demonstration device allows simultaneous monitoring of sweat rate/loss, along with quantitative measurements of pH and of lactate, glucose and chloride concentrations using biofuel cell and colorimetric approaches.