Design and optimization of isotropic stretchable strain sensors for multidirectional monitoring

Multidirectional monitoring is highly expectable for stretchable strain sensors by which the randomly orientated cracks or the maximum strain of all directions need to be accommodated. Many current types of research exploit laminated sensors and rosette designs to obtain the desired behavior in several discrete directions. However, this can lead to complex fabricating and resolving processes, as well as significant measurement errors. Our work proposes an isotropic stretchable strain (ISS) sensor that utilizes the in-plane curved sensing film from graphene/silver nanowires (AgNWs), which exhibits uniform sensitivity in all directions within 30^∘ and the potential extending to 360^∘. The ISS sensor, whose curved shape is optimized based on splines and the quantitative sensing model, is fabricated by a flash stamp machine and followed by vacuum filtration. Experimental results show that the ISS sensor possesses equivalent sensing properties in 30^∘ with excellent linearity and durability. Thus our customized sensor is applied to multidirectionally monitor the stretchable surface without consideration for the sensor orientation and the resolving process. Most importantly, the ISS sensor and its design method provide an efficient route for future sensor design with expected properties, not limited to isotropy.