An adaptive bionic sensor: enhancing ankle joint tracking with high sensitivity and superior cushioning performance

The bionic coupling structure hydrogel has excellent cushioning and conductivity, and is composed of MXene nanosheets incorporated into a polyvinyl alcohol and sodium alginate matrix. The hydrogel has high sensitivity and excellent stability, and can be used to monitor the motion status of the human ankle joint in real-time, thereby assisting users in making real-time judgments on gait health. [Display omitted] •Multi-level bionic structures can significantly improve the cushioning and sensitivity performance of hydrogels.•Compared with unstructured hydrogel, the displacement deformation of the bionic coupling structure hydrogel can be reduced by 91.22%, while the adhesion strength can be increased by 57.5%.•The designed sensor can simultaneously monitor and protect the ankle joints of wearer and quantitatively collect the ankle joint movement angles. Flexible sensors are renowned for their rapid responsiveness, high flexibility, and outstanding mechanical properties, making them ideal for applications in wearable devices, sports and health monitoring, and human-machine interfaces. To enhance the sensing performance of these flexible sensors, researchers have drawn inspiration from nature, creating various bionic microstructures. However, these structures often manifest in the macroscopic form of thin films, which do little to improve impact resistance and joint protection. In response, this work achieves a highly sensitive and impact-resistant pressure sensor by integrating bionic principles at both micro and macro levels. Specifically, at the micro level, a muscle-like hydrogel system consisting of MXene nanosheets incorporated into the double network of polyvinyl alcohol and sodium alginate matrix is selected. At the macro level, the bionic prototypes of mimosa leaves and durian spikes with good energy absorption structure, together with octopus’ sucker with good adsorption capacity are selected, and the synergistic construction of the three structures is realized through 3D printing methods. The obtained sensor has an appropriate response range, sensitivity and stability. More importantly, the displacement deformation of the hydrogel can be reduced by 91.22%, while its adhesion strength can be increased by 57.5% compared to the unstructured hydrogel. As a proof-of-concept, the proposed bionic flexible sensor can be used to monitor the motion status of the human ankle joint in real-time, thereby assisting users in making real-time judgments on gait heal