Alleviation of the adhesive protrusion problem at the bonding interface of free-standing microstructures

Abstract

The vertically allocated free-standing SU-8 microstructures are typically bonded to a glass cover by the usage of uncrosslinked SU-8 adhesives. Such a phenomenon can easily cause SU-8 protrusion and eventually result in the SU-8 cantilever to be immovable. Traditional methods are sensitive to the bonding conditions and have a short bondable thickness of SU-8 adhesives. In this study, we propose an approach, that is, improved structural features, to alleviate the protrusion problem while extending the bondable thickness for the freestanding SU-8 microstructures in an enclosed channel. We used concave and moat microstructures as solutions of the improved structural features. We investigated the influence of both microstructures on the bonding quality and compared the bondable thickness with the previous one. THB-151N was used in another example to demonstrate the availability of our method. The bonding quality at the interfaces was evaluated by SEM images and direct inspection through a transparent glass cover. The bonding method is advantageous to other microfluidic systems, particularly those with long narrow channels.