Fabricating SU-8 Photoresist Microstructures with Controlled Convexity–Concavity and Curvature through Thermally Manipulating Capillary Action in Poly(dimethylsiloxane) Microholes

Abstract

We present a simple, robust, and cheap microfabrication method, based on thermally manipulating capillary action in poly(dimethylsiloxane) (PDMS) microholes, for preparing SU-8 curved microstructures. The microstructure morphology including convexity−concavity and curvature can be controlled via tuning the formation temperature. The convex SU-8 microspherical crowns with a height of 40 μm were formed at 10 °C, whereas the concave SU-8 microspherical crowns with a height of 90 μm were formed at 100 °C. The morphology of the microstructures is dictated by the thermally controlled combination of the pressure difference across the interface, contact angle, and surface tension. The fabricated microstructures with a spherical surface can be used as a microlens array or a mold for producing a microlens array. The clear and uniform images were observed using the generated microlens arrays. The equilibrium morphology of the microstructures can be predicted by numerical simulation, which can lessen the number of experiments and thus the design cost. The proposed method has the potential to find applications in industrial fields.

Concave microlens arrays with tunable curvature for enhanced photodegradation of organic pollutants in water: A non‐contact approach

“…In direct fabrication methods, no templates are required, and concave MLAs are directly obtained. For example, mechanical machining, [26][27][28] thermal manipulating, 29,30 or direct laser writing [31][32][33] helps to create indentations that function as MLAs on the surface of matrices. Chemical wet-etching is another method to directly form concave MLAs, where materials on the unprotected regions can be selectively removed after being immersed into etchants.…”