Highly stretchable strain sensors based on gold thin film reinforced with carbon nanofibers

Abstract

Flexible piezoresistive sensors are often fabricated by depositing a conductive layer such as platinum, gold, graphene thin films, or conductive nanoparticles onto an elastic substrate. However, due to the intrinsic brittleness of the conductive materials, this method usually results in sensors with limited stretchability. Herein, we demonstrate a new technique to greatly increase the stretchability of piezoresistive strain sensors based on gold (Au) thin films by being hybridized with carbon nanofibers (CNFs). Sensors based on Au thin film fail electrically at a very small strain (∼ 4.5%). In contrast, the sensors based on hybridized Au-CNFs thin film show a significantly increased failure strain up to ∼ 225%. Introducing one-dimensional CNFs enables a greatly enlarged workable strain range by bridging and deflecting the microcracks formed in the Au thin film during stretching. This can effectively prevent the formation of lengthy, channel-like straight cracks that cause electrical failure under low strains. The high-performance sensors have shown great potential for use as wearable sensors for motion detection, such as detecting joint bending. Moreover, the potential of the sensors in detecting airflow similar to human respiratory airflow level has been demonstrated.