Atmospheric pressure atomic layer deposition for in-channel surface modification of PDMS microfluidic chips

Polydimethylsiloxane (PDMS) is one of the materials of choice for the fabrication of microfluidic chips. However, its broad application is constrained by its incompatibility with common organic solvents and the absence of surface anchoring groups for surface functionalization. Current solutions involving bulk-, ex-situ surface-, and in-situ liquid phase modifications are limited and practically demanding. In this work, we present a simple, novel strategy to deposit a metal oxide nano-layer on the inside of bonded PDMS microfluidic channels using atmospheric pressure atomic layer deposition (AP-ALD). Using three important classes of microfluidic experiments, i.e., (i) the production of micron-sized particles, (ii) the cultivation of biological cells, and (iii) the photocatalytic degradation in continuous flow chemistry, we demonstrate that the metal oxide nano-layer offers a higher resistance against organic solvent swelling, higher hydrophilicity, and a higher degree of further functionalization of the wall. We demonstrate the versatility of the approach by not only depositing SiO x nano-layers, but also TiO x nano-layers, which in the case of the flow chemistry experiment were further functionalized with gold nanoparticles through the use of AP-ALD. This study demonstrates AP-ALD as a tool to broaden the applicability of PDMS devices. • AP-ALD enables in-channel deposition of a nano-layer on bonded PDMS devices. • The morphology of the nano-layer is controlled by the number of AP-ALD sequences. • Three case studies show that AP-ALD widens the applicability of PDMS devices. • The approach’s versatility is shown by depositing nano-SiO x , nano-TiO x , and AuNPs.