Fully Integrated Wireless Elastic Wearable Systems for Health Monitoring Applications

Advances in flexible and hybrid electronics promote increasing demands for wearable sensors in personal health, monitoring, and diagnostic medical gadgets. Conventional wearable devices rely on electronics based on rigid substrates and components with limited conformity to user skin. In this work, we report a fully integrated, stretchable wireless electrocardiography (ECG) system developed on highly elastic, ultra-thin ( 100~\mu \text{m} ) thermoplastic polyurethane (TPU) film without any rigid or flexible interposer. Moreover, the circuit layout printing and component assembly are carried out through sheet-to-sheet (S2S) process directly on TPU film. This study utilizes both experimental reliability tests coupled with data acquired from finite element modeling (FEM) to assess performance and failure of the device under tensile loading. In such a complex system assembly, FEM simulation not only provides insights on the overall electromechanical performance of the device, but also facilitates localization of the failure points which are difficult to access for visual inspection. The performance of the device is also evaluated through controlled uniaxial cyclic strain at 5% and 10% elongation. The durability test shows that the assembled device can stay functional over hundreds of deformation cycles, suggesting that direct assembly of conventional components on stretchable substrate represents a promising approach for fully integrated stretchable devices, which is a step toward scalable manufacture of wearable stretchable electronics through high-throughput manufacturing processes.