Formation of a Controllable Diffusion Barrier Layer on the Surface of Polydimethylsiloxane Films by Infrared Laser Irradiation

Developing a diffusion barrier layer on material interfaces has potential applications in various fields such as in packaging materials, pharmaceuticals, chemical filtration, microelectronics, and medical devices. Although numerous physical and chemical methods have been proposed to generate the diffusion barrier layer, the complexity of fabrication techniques and the high manufacturing costs limit their practical utility. Here, we propose an innovative approach to fabricate the diffusion barrier layer by irradiating poly(dimethylsiloxane) (PDMS) with a mid-infrared (λ = 10.6 μm) CO₂ laser. This process directly creates a diffusion barrier layer on the PDMS surface by forming a heavily cross-linked network in the polymer matrix. The optimal irradiation conditions were investigated by modulating the defocusing distance, laser power, and number of scanning passes. The barrier thickness can reach up to 70 μm as observed by the scanning electron microscope (SEM). The attenuated total reflectance (ATR), electron dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS) analyses collectively confirmed the formation of the SiO_x structure on the modified surface based on the decreased methyl group signal and the increased oxygen/silicon ratio. The diffusion test with the model drugs (rhodamine B and donepezil) demonstrated that the modified surface exhibits effective diffusion barrier properties and the rate of drug diffusion through the modified barrier layer can be controlled by the optimization of the irradiation parameters. This novel approach provides the possibility to develop a controllable diffusion barrier layer in a biocompatible polymer with prospective applications in the fields of pharmaceuticals, packing materials, and medical devices.