Robust surface-subsurface modification of PDMS through atmospheric pressure atomic layer deposition

Polydimethylsiloxane (PDMS) has been widely employed as a material for microreactors and lab-on-a-chip technologies. However, in its applications, PDMS suffers from two major problems: its weak resistance against common organic solvents and its chemically non-functional surface. To overcome both issues, atmospheric pressure atomic layer deposition (AP-ALD) can be used to deposit an inorganic nano-layer (TiO x ) on PDMS that in turn can be further functionalized. The inorganic nano-layer is previously communicated to durably increase the organic solvent resistance of PDMS. In this study, we investigate the possibility of this TiO x nano-layer in providing surface anchoring groups on PDMS surfaces, enabling further functionalization. We treat PDMS samples cured at three different temperatures with AP-ALD and measure the hydrophilicity of the treated samples as an indicator of the presence of surface anchoring groups. We find that all the treated PDMS samples become hydrophilic right after the AP-ALD treatment. We further find that the AP-ALD-treated PDMS samples cured at 150 ° C and 200 ° C maintain their hydrophilicity, while the samples cured at 70 ° C become less hydrophilic over time. The presence of surface anchoring groups through TiO x nano-layer deposition on PDMS is further demonstrated and utilized by depositing gold nanoparticles (AuNPs) on the AP-ALD-treated samples. The samples exhibit visible light absorbance at 530 nm, a typical absorbance peak for AuNPs. In conclusion, this study demonstrates the use of nano-layers grown by AP-ALD to solve the two major problems of PDMS simultaneously, widening the PDMS applicability, especially for use in high-end applications such as catalysis and bio-sensing.