Fabrication of inkjet-printed SU-8 photoresist microlenses using hydrophilic confinement

Abstract

Inkjet-printed microlens arrays (MLAs) were fabricated using hydrophilic confinement by UV/ozone treatment. The MLAs were made from negative photoresist SU-8 (n = 1.63 at 530 nm). A film of 10 µm thick SU-8 shadow mask was used to define UV/ozone-treated hydrophilic zones on an SU-8 photoresist base layer. An inkjet print head was used to jet SU-8 photoresist drops onto these zones. After UV-curing, MLAs with diameters of 150, 200, 400, 800 and 1000 µm were successfully fabricated. Contact angles of MLAs increased from 22° (on MLAs fabricated using an SU-8 photoresist base layer without any surface treatment) to 45.5°, 47.7°, 52.4°, 51.3° and 54.2°, for 150, 200, 400, 800 and 1000 µm lens diameters, respectively. Using hydrophilic confinement, MLAs with a wide range of contact angles can be fabricated with diameters from 150 µm to 1 mm. This method provides a simple, cost-effective fabrication process without need for etch-transfer.