SU-8 is a high contrast, epoxy-based photoresist designed for micromachining and other microelectronic applications where a thick chemically and thermally stable image is desired. The exposed and subsequently cross-linked portions of the film are rendered insoluble to liquid developers. SU-8 has very high optical transparency above 360 nm, which makes it ideally suited for imaging near vertical sidewalls in very thick films. SU-8 is best suited for permanent applications where it is imaged, cured and left in place.