Ultrasoft\nConducting Polymer Hydrogels with Large\nBiaxial Strain and Conformal Adhesion for Sensitive Flexible Sensors

Conducting polymer hydrogels have\nbeen considered as\npromising\nmaterials for flexible sensors. The integrated performances of ultrasoftness,\nhigh deformation, mechanical robustness, conformal adhesion, and high\nsensitivity are of great importance for their applications in wearable\nsensors but still remains challenging. Herein, a highly deformable\nconducting polymer hydrogel with ultrasoftness, tear resistance, and\nself-adhesiveness is fabricated by incorporating poly(3, 4-ethylenedioxythiophene):poly(styrene\nsulfonic acid) (PEDOT:PSS) and silk sericin (SS) into a covalently\ncross-linked polyacrylamide (PAM) network. Owing to abundant noncovalent\ninteractions among the folded SS chains, PAM chains, and PEDOT:PSS,\nthe obtained hydrogel shows a low modulus (10.3 kPa), ultrastretchability\n(>2000%), particularly large biaxial strain (an areal strain of\n1700%),\nhigh toughness (tearing energy of 2.5 kJ/m<sup>2</sup>), and good\nconformal adhesion. As a result, this hydrogel demonstrates superior\nstrain-sensitivity (gauge factor = 13.8) in a broad strain range (2000%)\nand excellent sensing reproducibility. The hydrogel-based wearable\nsensor can be used for accurately monitoring large and tiny human\nmovements in real time and serves as bioelectrodes for precise gathering\nof electrocardiography and electromyography signals, showing great\npotential for applications in flexible sensing devices.