Carboxyethyl acrylate incorporated optically clear adhesives with outstanding adhesion strength and immediate strain recoverability for stretchable electronics

Since the development of the 5G network, wireless and user-oriented electronics are rapidly emerging. In response to demands for wearable devices, which are curved, bendable and/or stretchable, all components of electronics are required to be flexible. Moreover, the assembly of these components is challenging issue, because the conventional adhesives used in displays are typically rigid unsuitable for flexible electronics. Therefore, developing elastic pressure-sensitive adhesives (PSAs) is critical for the commercialization of flexible electronics. In this study, UV curable acrylate-based PSAs are synthesized using 2-carboxyethyl acrylate (CEA) as a functional monomer, and exhibit exceptionally strong peel adhesion and good flexibility. The synthesized film also exhibits adequate transmittance (>95%) to be used as an optically clear adhesive. The stress-relaxation and strain-recovery behavior of the PSAs at various conditions is evaluated and analyzed in detail. To induce elastic characteristics in the PSAs, a pre-straining strategy is implemented, which triggers a purely elastic characteristic with instantaneous strain recovery. The pre-strained PSAs were able to withstand 5000 cycles of repetitive stretching and bending tests; thus, the synthesized PSAs can provide wide range of applications, including stretchable displays and epidermal devices.