Surface micro-structured, stretchable strain sensor towards biaxial sensitivity and performance enhancement

In this work, we developed micro-crack based stretchable strain sensors consist of polydimethylsiloxane (PDMS) with micro-dome structure arrays and carbon nanotube (CNT) film coated on its surface. Due to a stress concentration caused by micro-dome structure under a certain strain, micro-cracks of CNT film are generated and propagated more easily as compared with the case of a CNT film on the plane surface. In addition, because the micro-cracks are only positioned at designed region which is between micro-domes, electrical resistances in elongated and perpendicular directions are clearly different thanks to the novel mechanism. As results of these phenomena, strain decoupling is achieved and a sensitivity of the sensor can be modulated by adjusting the dimension of micro-dome arrays. We also conducted the numerical simulation based on finite element method (FEM) to verify the designed sensing mechanism and predict the performance of the sensor. This kind of work is important for the motion detecting sensor for acquiring decoupled information from complex signal. Finally, we fabricated a smart glove that could detect a biaxial strain applied on the back of a hand skin to demonstrate that this sensor could be used as wearable device.