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

We present a simple, robust, and cheap micro fabrication 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 mu m were formed at 10 degrees C, whereas the concave SU-8 microspherical crowns with a height of 90 mu m were formed at 100 degrees 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.

Automated summary

We propose a simple, robust, and cheap micro fabrication method using thermally manipulating capillary action in PDMS microholes to prepare SU-8 curved microstructures. The microstructure morphology, including convexity-concavity and curvature, can be controlled by adjusting the formation temperature. The fabricated microstructures with a spherical surface can be used as a microlens array or a mold. Clear and uniform images were observed using the generated microlens arrays. The proposed method has the potential for industrial applications.