Study on the fabrication of a SU-8 cantilever vertically-allocated in a closed fluidic microchannel

This paper describes the fabrication of a vertically-allocated SU-8 cantilever in a closed fluidic channel. The difficulties to fabricate the vertically-allocated SU-8 cantilever inside the closed channel mainly lie in which kinds of sacrificial layers under the cantilever and sealing methods for enclosing the channel are utilized for the movability of the cantilever. To obtain a suitable sacrificial layer and high sealing quality, the selectivity of sacrificial layers and the sealing conditions based on the SU-8 adhesive are discussed in this paper. The experiments to test different photoresist lead to the conclusion that AZ 5214E is adequate for the sacrificial layer. Also, the bonding results indicate that the thickness of the uncrosslinked SU-8 solid layer is the most important factor which affects the formation of a proper gap between the top coverglass and the SU-8 cantilever. The photos of the movement of the cantilever also show that the free-standing SU-8 cantilever is successfully fabricated by releasing the suitable sacrificial layer and is allocated inside the closed channel by the method of SU-8 adhesive. The fabrication method in this paper is also useful for other microfluidic applications.