Transfer Printing Technology on 3D Curvilinear Surfaces Using Shape Deformable PVA-Based Stamp for e-Skins

Stretchable and flexible electronics have attractive applications in wearable devices by transforming rigid configurations into ultrathin, skin-like forms that wrap around the skin. Conventional planar elastomer stamp-based transfer printing techniques face significant challenges in printing onto complex curved surfaces, particularly in regions with small radii of curvature, such as the fingertips or the narrow spaces between fingers, while maintain conformal lamination. Here, we demonstrate a fabrication method for conformal printing on sophisticated three-dimensional(3D) curvilinear surfaces using shape deformable polyvinyl alcohol(PVA)-based transfer printing. The proposed stamp enables the transfer of a pattern array from a negative surface to a positive surface by minimizing stress and conforming its shape to the receiver substrate, thereby ensuring conformal contact with the pattern array. Shape deformable stamp printing, which exhibits good adhesion and ease of deformation, provides significant advantages for printing on curvilinear surfaces and enables the creation of electronic skin(e-skin) by printing on low modulus substrates, such as skin. To illustrate the capabilities of this approach, we demonstrate the transfer onto highly contoured regions, such as the ear, fingerprints and skin wrinkles. This research presents potential application for 3D electronics, including innovative uses like skin displays with mini-LEDs and contact lenses integrated with antennas. Furthermore, the concept of electronic skin emerges as a prominent feature within our proposed applications. This study highlights the potential impact of this research on the future landscape of wearable electronic technology.