A novel combination of graphene and silver nanowires for entirely stretchable and ultrasensitive strain sensors: sandwich-based sensing films.

A great deal of engineering effort is focused on developing stretchable strain sensors for human motion monitoring and wearable devices. The ultrasensitivity and fast response under tiny strain (1%) while maintaining the working range remain the grand challenge. In this work, we propose an entirely stretchable strain sensor based on the sandwich sensing film, which is fabricated by vacuum filtration of silver nanowires (AgNWs)/ graphene/ AgNWs in sequence and the injection of liquid metal as electrodes. The novel sandwich sensing film endows the stretchable strain sensor high sensitivity under tiny strain (Gauge factor = 111.5 at 1%), fast response (<10 ms), relative large working range (0%-35%) with a maximum gauge factor of 1403.7, followed by good linearity, long-term durability, and the recovery property from being overstretched (>100%). The excellent performance is due to the slippage of the inner graphene under tiny strain, whereas the 'sewing' phenomenon of the outer AgNWs under larger strain. The sandwich structure illustrates a better combination of graphene and AgNWs than other hybrid methods, showing great potential in wearable devices and soft robotics.