Long-term hydrophilic PDMS surfaces using Brij L4: A simple and robust approach for biomedical applications

Polydimethylsiloxane (PDMS) is a widely used material in the production of microfluidic devices and biomodels, due to its exceptional mechanical, chemical and biocompatible properties. Recently, a novel class of devices known as microphysiological systems have emerged, combining microfluidic technology and cell culture, mimicking the microphysiological features of the human body to facilitate the study of both healthy and pathological conditions. However, the hydrophobic nature of PDMS leads to several drawbacks including high fluid flow resistance, and non-specific molecule adsorption which impact the growth and proliferation of cell culture and the specificity of biochemical assays. The most popular technique to improve the PDMS surface wettability is the application of air or oxygen plasma treatment to its surface, providing only temporary effects and requiring specialized and high-cost equipment. Another strategy is modifying the bulk of the material by adding components to PDMS during the manufacturing process. By applying the latter approach, the present work presents a simple, robust, and low-cost method to modify the PDMS wettability for a long period of time. PDMS surfaces were modified using various concentrations of Brij L4 surfactant, either applied directly (bulk) or in combination with plasma treatment, and their performance was compared to the most commonly used traditional method, i.e., the oxygen plasma treatment. The PDMS surface’s wettability was assessed from a short period of time (hours) up to five months, demonstrating that the proposed method achieves stable hydrophilicity. Optical, morphological and mechanical surface properties, were observed to confirm that hydrophilic and transparent PDMS surfaces were successfully obtained. The non-specific adsorption was tested using serum albumin, and a significant adsorption reduction was observed. This innovative approach provides a simple, effective and unexpensive way to achieve stable PDMS wettability for a long-term period.