Multifunctional PVA/PNIPAM conductive hydrogel sensors enabled human-machine interaction intelligent rehabilitation training

Hydrogels are regarded as an ideal medium for human-machine interaction (HMI) due to their adjustable modulus and flexibility, enabling seamless interaction with smart devices. However, in the field of medical rehabilitation, most of the hydrogel-based sensors are simply used to detect the motion signals of fragments and are rarely applied to help patients with rehabilitation training and improve the efficiency of doctors’ diagnosis. This is due to the unstable sensing properties and poor mechanical properties of most hydrogels. The poor durability greatly limits the application of hydrogel-based sensors. Here, a conductive hydrogel sensor with visual temperature sensitivity and good mechanical properties (300% strain, breaking stress 0.19 MPa) is fabricated by introducing polyvinyl alcohol (PVA)-borax system combined with a freeze-thaw physical regulation strategy. The PVA/PNIPAM/PEDOT: PSS (PPP) hydrogels possess a rapid response/recovery time (200 ms/200 ms), a low detection limit of 1% strain, and good stability and durability. Furthermore, by integrating the hydrogels with a LabVIEW circuit program and wireless transmission technology, we have created an advanced intelligent HMI system that facilitates monitoring, rehabilitation training, and remote diagnosis.

Graphical Abstract

The conductive hydrogel sensor with visual temperature-sensitive change and excellent mechanical properties has been successfully prepared by introducing PVA-borax system and freeze-thaw physical regulation strategy. The breaking strain of PVA/PNIPAM/PEDOT: PSS hydrogels achieves 300%, and the breaking stress achieves 0.19 MPa. As a strain sensor, due to the presence of the conductive polymer PEDOT: PSS, PPP hydrogel has a fast response/recovery time (200 ms / 200 ms), a low detection limit of 1% strain, and good stability and durability, enabling accurate monitoring of various human movements. By further combining PPP hydrogel sensor with the LabVIEW circuit program and wireless transmission technology, an advanced intelligent HMI system integrating monitoring, rehabilitation training and remote diagnosis has been constructed.