Fabrication of flexible electrodes using peelable pressure-sensitive adhesives containing methacrylic-modified cyclic siloxanes

Since the emergence of flexible devices, such as foldable smartphones, methods for manufacturing flexible electrodes have received much attention. In this work, we fabricated a peelable pressure-sensitive adhesive (PSA) and used it for temporary bonding and debonding processes to produce a flexible electrode. First, we synthesized a methacrylic-modified cyclic siloxane (MeD4) starting from a cyclic siloxane (HD4), and this was admixed with an acrylic polymer to afford peelable PSAs. With the addition of MeD4, the peeling adhesion of PSA-5 was reduced by two orders of magnitude after UV irradiation. The decrease in peel strength was ascribed to the crosslinking of MeD4, which hardened the UV-cured PSA-5. Then, we utilized PSA-5 to fabricate a flexible electrode. For this, a cPI film was attached on a glass substrate via PSA-5, and aluminum (Al) patterns were fabricated on the cPI film through sputtering deposition, photolithography, and etching processes. Thanks to the low peeling adhesion of the UV-cured PSA-5, the flexible electrode was easily detached from the glass without any deformation of the Al patterns. The electric property of the flexible electrode was stable after 10,000 U-shape folding test cycles.