Wearable chemical sensing – optimizing fluidics for real-time sweat analysis

Abstract

This work presents the optimization of electrical parameters and sampling platforms to maximize the sensitivity of conductivity measurements for applications in wearable sweat sensing. Conductivity in sweat is related to electrolyte content and offers valuable information for hydration, athletic performance and nutrition. The most abundant ions of sweat electrolytes are sodium and chloride, making sweat conductivity directly related to their concentration [1]. Capacitively coupled contactless conductivity detection (C4D) was used to test the response of commercial gold microelectrodes (figure A). This work was done in preparation for the development of an on-body detection system for sweat analysis. On body testing requires sample handling specific to the method of testing, which in this case is non-contact. For this type of handling, polydimethylsiloxane (PDMS) and poly(methyl methacrylate) (PMMA) microchannels of various configurations were tested for their compatibility with the system and the effect of their geometry on signal sensitivity. Figures B-D show the dimensions of one such PMMA channel from top, bottom and expanded side view, respectively