Surface Structure Engineering for Bionic Fiber-Based Sensors toward Linear, Tunable and Multifunctional Sensing

Flexible and stretchable strain sensors have broad applications in human physiological activities, object deformation, as well as human-machine interface. However, it is still of challenge to fabricate stretchable strain sensors with linear and superior piezoresistive signal response. Here, we report a facile and scalable structure design strategy to generate segmental hierarchical fiber surface structure, mimicking the arthropod body and lobster tail structure, on electrospun core-sheath polymer fiber (thermoplastic polyurethane (TPU) core and polystyrene (PS) sheath) mats for tunable strain sensing performance. Due to distinct modulus difference between the core and sheath layers, such fibers generate various periodic PS-knot distributions via different pre-strains, enabling initiating significant strain concentration effect to improve tunable sensing properties, e.g. linear degree varies from 0.48 - 0.99 and gauge factor ranges from 5.25 to 23800 for the strain within 30%. The bionic structured fiber sensors demonstrate potential applications in detection of human skin epidermis disturbance, small curvature changes, sound wave vibration, as well as mechanochromic response if adding a fluorescent agent to the TPU core. Besides, they are also capable of detecting various types of organic vapors due to heterogeneous structure design, paving a new way to design multifunctional flexible sensors for variable human-machine interface applications.