Highly Aligned, Anisotropic Carbon Nanofiber Films for Multidirectional Strain Sensors with Exceptional Selectivity

Abstract Realization of sensing multidirectional strains is essential to understanding the nature of complex motions. Traditional uniaxial strain sensors lack the capability to detect motions working in different directions, limiting their applications in unconventional sensing technology areas, like sophisticated human–machine interface and real‐time monitoring of dynamic body movements. Herein, a stretchable multidirectional strain sensor is developed using highly aligned, anisotropic carbon nanofiber (ACNF) films via a facile, low‐cost, and scalable electrospinning approach. The fabricated strain sensor exhibits semitransparency, good stretchability of over 30%, outstanding durability for over 2500 cycles, and remarkable anisotropic strain sensing performance with maximum gauge factors of 180 and 0.3 for loads applied parallel and perpendicular to fiber alignment, respectively. Cross‐plied ACNF strain sensors are fabricated by orthogonally stacking two single‐layer ACNFs, which present a unique capability to distinguish the directions and magnitudes of strains with a remarkable selectivity of 3.84, highest among all stretchable multidirectional strain sensors reported so far. Their unconventional applications are demonstrated by detecting multi‐degrees‐of‐freedom synovial joint movements of the human body and monitoring wrist movements for systematic improvement of golf performance. The potential applications of novel multidirectional sensors reported here may shed new light into future development of next‐generation soft, flexible electronics.