Play on Electrodes

Maximizing the efficiency of electrode usage is a crucial step in enhancing the integration of wearables. Currently, electrodes are combined in an additive manner to enable multiplexed sweat screening. The additive sensor requires significant space to accommodate single-function electrodes, which limits the integration of the wearable sensors. Here, we report that the versatility of a single electrode is achieved by assigning different roles to the electrode at different times, resulting in a flexible, disposable, epidermal sweat-sensing platform that integrates in situ iontophoresis and three electrochemical sensors on only four electrodes, while previous platforms required at least seven electrodes. For example, the iontophoresis electrode serves as the working electrode (WE) for chloride sensing and as the counter electrode (CE) for pH sensing after its controllable release of pilocarpine, and the sulfonated polyaniline (SPAN) modified glucose oxidase (GOx) serves as the WE for both pH and glucose sensing. All four functions are integrated into an 8 mm2 (1.8 × 4.45 mm) sensing area, requiring a sample volume of approximately 1 μL. These results open possibility for highly integrated wearable sweat sensors and multimodal sensors.