Skin-Inspired Healable Conductive Elastomers with\nExceptional Strain-Adaptive Stiffening and Damage Tolerance

Abstract

Stretchable\nconductive elastomers play an irreplaceable role in\nflexible electronic devices. However, stretchable conductive elastomers\nare usually soft and susceptible to damage. In this study, inspired\nfrom skin, highly stretchable and elastic conductive elastomers integrated\nwith damage resistance, damage tolerance, and healability are fabricated\nby loading ionic liquids (ILs) within the polyurethane (PU) elastomers\nof the multiblock polymers of poly­(dimethylsiloxane) (PDMS)/polycaprolactone\n(PCL) coordinated with Zn²⁺ ions. The mechanically robust\nconductive elastomer, with a tensile strength of ∼15.2 MPa\nand a stretchability of ∼2668%, has a satisfactory ionic conductivity\nof 2.9 × 10^–4 S cm^–1. The\nconductive elastomer exhibits exceptional strain-adaptive stiffening,\nwith an ∼100-fold increase in modulus when being fully stretched.\nThe strain-adaptive stiffening endows the elastomer with excellent\ndamage resistance. Meanwhile, the conductive elastomer has a record-high\nfracture energy of ∼33.8 kJ m^–2. The notched\nconductive elastomer can prevent the propagation of the notch up to\na strain of ∼2400%. The exceptional strain-adaptive stiffening\nand damage tolerance originate from the <i>in situ</i> formed\nphase-separated domains, which are deformable and disintegrable under\nan external force to significantly strengthen the elastomer and dissipate\nenergy. Furthermore, the conductive elastomer can be conveniently\nhealed under heating to restore its original conductivity and mechanical\nproperties.