A hyperelastic adhesive forming multiple neutral planes even at extreme temperatures

To relieve strain applied to foldable devices, multiple neutral planes (MNPs) strategy with soft adhesive has been employed. However, rheological properties of adhesive are highly dependent on temperature; rigid at low temperature and excessively soft and viscous at high temperature. In addition, the adhesive must rapidly recover to its original shape as soon as it is unfolded after being deformed by folding. This ensures both quick and dependable folding/unfolding operations for the foldable devices. Here, polydimethylsiloxane (PDMS)- vapor-phase interpenetrating adhesive (PDMS-VIA) is suggested. PDMS possesses extremely low glass transition temperature (<-120 degree celsius), and whose crosslinking structure enables hyperelastic behavior. An adhesion promoting layer (APL) was newly developed to improve the poor adhesion of PDMS, making interlocking structure with the surface of PDMS. The PDMS-VIA demonstrates robust adhesion to various substrate materials, rapid strain recovery, and exceptional stability against folding/unfolding cycles over a wide range of temperature from -50 to 100 degree celsius. The soft but highly reliable adhesive with temperature-independent rheological properties, will serve as a laminating platform method for foldable devices with an unprecedented temperature range able to form MNPs without temperature-related failure.