Fabrication of interconnected multilevel channels in a monolithic SU-8 structure using a LOR sacrificial layer

• A process to obtain multilevel microchannels in a monolithic SU8 structure was optimized.
• We used LOR and SU8 resists in combination for an innovative lithographic approach.
• A tool for biological applications in the lab-on-chip field was realized.

The development of new microfabrication techniques is attracting more and more interest because of the increasing demand for three-dimensional tools with features of biocompatibility, flexibility and low-costs in the lab-on-chip field. Photolithographic techniques involving the molding of organic polymers, like SU-8, allow for short fabrication times and simplicity in devices prototyping. In this paper we used LOR and SU-8 resists in combination within an innovative lithographic approach. LOR resist was employed not as a typical sacrificial layer for the production of free-standing structures but as a three-dimensional solid resist, which can be patterned and embedded in a SU-8 monolith. After dissolution it can form cavities to provide a final multilevel structure. A detailed description of the optimization process required to obtain the final structure and to overcome issues related to the employ of LOR is reported. In the end, a network of working interconnected multilevel microchannels, useful for biological applications, has been realized through a new, cheap and time-saving method.

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