Adhesive-free bonding of PI/PDMS interface by site-selective photothermal reactions

Abstract Effective bonding between polyimide (PI) and polydimethylsiloxane (PDMS) is important for the development of both implanted and externally mounted biomedical devices; however, achieving an adhesive-free bonding between the two materials without using surface chemical treatments has been largely unsuccessful to date. We discovered that, within a narrow range of laser parameters, laser-induced photothermal reactions at a specific site on the PI/PDMS interface led to an unexpected reinforcement of the adhesion strength between the two materials. This result was verified by microscopic in situ observations in which PDMS residues were observed to remain on the PI surface after forced delamination. The effect of heat pulses on the PI/PDMS interface was evaluated on the atomic scale through molecular dynamics simulations, and the results showed that as the heat pulses were added, the roughness values of both the PI and PDMS surfaces increased, accompanied by an improvement in the elastic properties at the interface, thus increasing the effective adhesion energy per unit area. The incorporation of a scanning scheme enabled the continuous bonding of the two materials, demonstrating that the proposed process can be easily scaled up for practical applications.