An intrinsically stretchable multi-biochemical sensor for sweat analysis using photo-patternable ecoflex

Abstract

Ecoflex is widely used in bioelectronics due to its outstanding properties of low modulus and large stretchability. For its use as an encapsulation layer in multi-channel wearable devices, a patterning procedure is essential. However, conventional patterning strategies for Ecoflex, such as soft lithography, punching, and laser ablation, lack sufficient quality and process compatibility. To address this, we propose a process-compatible method of patterning Ecoflex by developing Photo-patternable Ecoflex (PPE). The PPE layer, used as an encapsulation layer, effectively dissipates strain energy at homogeneous interfaces, resulting in a 50% increase in electrical conductance under 250% strain. Using PPE, we fabricated intrinsically stretchable multi-sensors that monitor bio-signals like glucose, lactate, pH, and humidity in sweat. These sensors maintain durable sensitivity under strain up to 50% and for 1000 cycles at 20% strain. Finally, we mounted these stretchable multi-chemical sensors on an arm to monitor glucose and lactate levels in sweat.