Precision poly-(dimethyl siloxane) masking technology for high-resolution powder blasting

Powder blasting micro-erosion is a fast and flexible technique for the micropatterning of brittle materials. We have combined 10 μm diameter Al₂O₃ eroding particles with a new masking technique to realize the smallest possible structures with the powder blasting process (30 μm). Our masking technology is based on the sequential combination of two polymers: 1) the brittle epoxy resin SU8 for its photosensitivity and 2) the elastic and thermo-curable poly-(dimethyl siloxane) (PDMS) for its large erosion resistance. We have micropatterned glass microstructures with aspect ratio 1 and structural details down to 20 μm. We compare the mask size-dependent etching rate using both 1.0 and 30 jam diameter Al₂O₃ particles and find a decreasing etching rate for structures that are smaller than about 10 times the particle size. Combining SU8 with PDMS proves to be a very easy and accurate masking technology that allows exploring the fundamental dimensional limits of the powder blasting micro-erosion process.