Tuning Poly(dimethylsiloxane) Hydrophilization and Coating Stability via the Optimization of Polyethylene Glycol Molecular Weight

Polydimethylsiloxane (PDMS) is widely used in microfluidics and medical devices; however, its inherent hydrophobicity limits its applications. This can be resolved by the formation of polyethylene glycol (PEG)-based hydrophilic coatings. Here, we aimed to prove that PDMS surfaces modified with low molecular weight PEG (400) provided a more stable hydrophilic surface. The lowest contact angle achieved via using PEG400 and the "grafting from" approach was 8.6 ± 3.5°. Under perfusion conditions, imitating arterial and capillary flows, such coatings were considerably stable, and the contact angle was kept at 45.5° after 3 days. Moreover, the applied surface modifications preserved surface roughness, elastic modulus, and optical transparency. Thus, these findings confirmed that the "grafting from" approach with low molecular weight PEG could be the most effective strategy to form hydrophilic PDMS coatings with optimal performance in biomedical applications.