We report for the first time on a simple fabrication via UV photolithography for a free-standing filtration membrane made of epoxy-based photoresist and its integration on a multilevel microfluidic device. The fabrication process involves three-dimensional thick-photoresist microstructuring combined with standard negative photoresist processing. In this paper, a primary feature of membrane permeability dependence on fabrication process parameters was characterized by employing a cross-linking reaction model. The experiments using a multilevel microfluidic device demonstrated the proposed fabrication is capable of fabricating nano-filtration membrane while maintaining a sufficient mechanical strength for applications in polymer-based microfluidic devices. © 2011 IEEE.