Graded-modulus tri-layer substrates for stress-relieved direct fabrication of integrated stretchable systems

Stretchable electronics capable of integrating high-performance components while accommodating large mechanical deformations are increasingly in demand for wearable devices and soft robotics. Conventional substrates composed solely of soft materials exhibit limited mechanical and thermal tolerances for thin-film processing, whereas hybrid structures combining soft and rigid substrates exhibit severe interfacial stress and delamination caused by the large difference in Young’s modulus between the materials. This study proposes a tri-layer hybrid substrate made of Ecoflex, polydimethylsiloxane, and epoxy resin with graded Young’s moduli, which effectively relaxes the interfacial stress while maintaining mechanical and thermal stability. It withstands up to 300% tensile strain and enables the direct deposition of organic thin-film transistors and incorporation of integrated circuit components without any transfer process. This study presents a versatile platform capable of directly integrating rigid and thin-film electronic devices on a single substrate, thus paving the way for highly integrated and practical stretchable electronic systems.