Polymeric hemispherical pico-liter micro cups fabricated by inkjet printing

The fabrication of precise hemispherical shape is challenging with standard planar lithography techniques. A suitable alternative is the fabrication by inkjet printing. This paper presents a method based on drop-on-demand inkjet printing on pre-patterned silicon substrates allowing the controlled fabrication of SU-8 hemispherical cup-like structures with inner cavities of sub-nano-liter volumes. Examples are given for cups of 100μm in diameter with inner cavity volumes of 5pL, 20pL and 45pL. Arrays of 360 hemispherical SU-8 cups have been fabricated with a yield above 96%. The 4% of exceptions are also described and shown as a method for achieving almost complete SU-8 spheres.