Highly Stretchable and Multimodal MXene/CNTs/TPU Flexible Resistive Sensor with Hierarchical Structure Inspired by Annual Ring for Hand Rehabilitation.

With the advent of the intelligent age and people's higher pursuit of health, wearable sensors with functions of health monitoring and assisting physical rehabilitation are increasingly favored by consumers. Wherein, highly stretchable flexible sensors show promising potential, but the unstable conductivity under large strains remains a great challenge to develop flexible wearable sensors with both a wide work range and strain insensitivity. Based on this, a MXene/CNTs/TPU flexible resistive sensor (MCT/FRS) with hierarchical structure inspired by the annual ring was proposed. Benefiting from the bioinspired structure with tightly warped inner layers and deformable spring structure outside, the MCT/FRSs enable stable sensing over a wide working range of up to 700% under the stretching mode, as well as superior durability (7500 cycles). It also possessed linear and adjustable piezoresistive properties under the compression mode. Finally, the sensor was not only successfully employed for monitoring various human movements but also was utilized to assist hand rehabilitation in patients with Guillain-Barré syndrome in both stretching and compression modes. This work provides promising and attractive solutions for flexible wearable devices and intelligent medical care.