An innovative and rapid method for permanent hydrophilic modification of polydimethylsiloxane (PDMS) chip surfaces

Polydimethylsiloxane (PDMS), a fundamental material in the fabrication of microfluidic devices, suffers from nonspecific adsorption of biological samples due to its hydrophobic nature. Herein, by employing a radiation-induced grafting strategy to introduce hydrophilic functional groups onto the PDMS surface, a significant improvement in hydrophilicity is achieved, leading to a notable reduction in the contact angle by up to ∼90° and improvement of antifouling performance against biological samples. Effects between monomer concentration, grafting efficiency, and mechanical integrity are balanced to optimize the grafting process, achieving promised hydrophilicity enhancement while the mechanical properties are not degraded. The content of carboxyl groups exposed on the surface of grafted PDMS was computationally analyzed using MD simulations, which revealed the key role of carboxyl groups in the wettability of the PDMS surface. Our study extensively showcases the effective grafting of acrylic acid onto PDMS, which is characterized by diverse grafting rates. Remarkably, the hydrophilic modification is stable over time compared to conventional plasma treatment, offering a more reliable and enduring strategy, and making it a valuable enhancement for PDMS chips with extensive applications.