Ultra-robust bonding between MXene nanosheets and stretchable, self-healable microfibers

To develop a reliable fibrous device, a strong bond between conducting materials and fibers must be ensured. While the external surface of the film is relatively flat, making it easy to deposit the electrode materials uniformly, the walls of thepolymer fibers inside the porous film pose a greater challenge for ensuring a uniform coating and robust bonding with electrodematerial. Herein, a microfibril-based porous film was prepared by electrospinning polybutadiene-based urethane (PBU), a newlysynthesized self-healing polymer, and Ti₃C₂-based MXene nanosheets were coated thereon to fabricate a pressure sensor whoseresistance decreases with pressure. The PBU microfibrils were crosslinked under mild conditions via Diels-Alder (DA) reactionby exploiting low activation energy of the PBU. An exceptionally robust bonding between the PBU and MXene was enabled bysubjecting the PBU to a retro-DA and subsequent DA reactions. The temporary increase in surface fluidity of the PBU leaded toa conformal contact between the MXene and fibers without collapse of fibrous structure, resulting in an ultra-robust bondbetween them. A stretchable and self-healable pressure sensor was implemented by removing unnecessary MXenes by applyingultrasonic energy to the thus-fabricated sample. The fabricated sensor showed a pressure sensitivity of around 27.9 /kPa for awide range of pressure which is the highest level among the reported stretchable self-healing pressure sensors, while maintainingits performance even after 1000 cycles of stretching and pressing.