How the geometry of patterned surfaces affects the thickness distribution of the oxidized silica layer on polydimethylsiloxane (PDMS) after ultraviolet/ozone treatment

It is well established that a thin silica-like surface layer is formed when a cross-linked PDMS structure is subjected to ultraviolet/ozone treatment. Due to surface geometry, especially near the corners, this silica-like surface layer has non-uniform thickness, which can impact many mechanical properties, including adhesion and fracture strength. Here we use a simple analytic model based on diffusion of reactive species to predict the thickness of the oxidized surface layer near the corners. We demonstrate that these corner solutions can be patched together to determine the thickness of the oxidized layer in complex geometries. An analytic solution is presented to predict the non-uniform near-surface oxidized layer thickness when a cross-linked PDMS structure is subjected to ultraviolet/ozone treatment.