Laser-selective curing for enhancement of interlayer bonding of 3D-printing polydimethylsiloxane-based structures

Abstract

Polydimethylsiloxane (PDMS), renowned for its exceptional stretchability and biocompatibility, has been extensively employed as a flexible substrate for wearable and stretchable electronics. However, the functional failure of 3D-printed PDMS structures caused by insufficient interlayer bonding strength significantly limits their applications. To address this challenge, this study innovatively proposes a manufacturing method for selective PDMS curing based on photothermal conversion, in which polyimide (PI) film is introduced as an intermediate thermally conductive medium to enable selective laser heating and localized curing of highly transparent PDMS. This strategy not only provides structural support for functional layers via laser-selective curing of PDMS but also retains substantial uncured regions to enable covalent crosslinking between adjacent PDMS layers, thereby effectively improving the interlayer bonding strength. Moreover, the laser-cured zones are encapsulated within these uncured portions, further achieving the enhancement of interlayer bonding strength of PDMS-based 3D-printed devices. The results demonstrate that compared with conventional fully curing layer-by-layer printing approaches, the samples prepared by this strategy exhibited cohesive failure during the T-peel test, while pull-off testing demonstrated a minimum 2.36-fold enhancement in interfacial bonding strength, and optical microscopy observations at 20× magnification revealed no delamination at the interfaces. Leveraging this method, a flexible strain sensor with stable performance over 1,000 cycles and a microfluidic chip capable of withstanding a flow rate of 1000 μL/min without leakage were successfully fabricated.