Pyramid structure-inspired biocompatible bilayer hydrogel based on supramolecular interactions for stable human–machine interface

Flexible wearable sensors based on hydrogels have shown great potential in the fields of actuating, sensing, and human–machine interface. However, to cope with the drawbacks associated with all-in-one hydrogels, rational modulation of hydrogel design models and construction factors for preparing bilayer hydrogels with stable contact interfaces and comprehensive features remains challenging to be realized. Here, the pyramid structure-based AxCy bilayer hydrogels with stable interface were prepared using a layer-by-layer polymerization technique of tetradecyl methacrylate (TMA)-based conductive hydrogels and adhesive hydrogels based on monoacrylamide cucurbit[7]uril (AA1CB[7]). The hydrogels exhibited good mechanical properties (fracture strain and fracture stress were 1657.04% and 140.64 kPa, respectively), superior adhesion properties (154.14 kPa), and excellent biocompatibility (97.85% cell viability for NIH3T3). When being used as a flexible sensor, A0.1%C1.0% bilayer hydrogel can not only accurately monitor various body movement signals, but also physiological signals such as electrocardiogram (ECG) for a long time. Therefore, pyramidal structure-inspired bilayer hydrogels based on cucurbit[7]uril will present a promising application in the realm of human–machine interface.