Ultrastretchable,\nUltralow Hysteresis, High-Toughness\nHydrogel Strain Sensor for Pressure Recognition with Deep Learning

Hydrogel, as a promising material for a wide range of\napplications,\nhas demonstrated considerable potential for use in flexible wearable\ndevices and engineering technologies. However, simultaneously realizing\nthe ultrastretchability, low hysteresis, and high toughness of hydrogels\nis still a great challenge. Here, we present a dual physically cross-linked\npolyacrylamide (PAM)/sodium hyaluronate (HA)/montmorillonite (MMT)\nhydrogel. The introduction of HA increases the degree of chain entanglement,\nand the addition of MMT acts as a stress dissipation center and cross-linking\nagent, resulting in a hydrogel with high toughness and low hysteretic\nproperties. This hydrogel synthesized by a simple strategy exhibited\nultrahigh stretchability (3165%), high breaking stress (228 kPa),\nhigh toughness (4.149 MJ/m<sup>3</sup>), and ultralow hysteresis (≈2%\nat 100% of strain). The fabricated hydrogel flexible strain sensors\npossessed fast response and recovery times (62.5:75 ms), a wide strain\ndetection range (2000%), a strain detection limit of 1%, and excellent\ncycling stability over 500 cycles. Furthermore, the hydrogel flexible\nstrain sensor can be used for human motion monitoring, gesture recognition,\nand pressure recognition assisted by deep learning algorithms, showing\nenormous promise for applications.