A simple fabrication process for disposable interdigitated electrode arrays with nanogaps for lab-on-a-chip applications

In this paper, we introduce for the first time a novel fabrication process for interdigitated electrode arrays (IDA) with nanogaps on polymer substrates. The IDA sensor for disposable lab-on-a-chip (LoC) applications employs an amperometric detection principle which allows a signal amplification by redox cycling. Our fabrication sequence is based on a lift-off free process and therefore, reduces the number of process steps and simplifies the fabrication and increases the yield. This innovative approach consists of an initial structure followed by two deposition processes. The initial structure, which is transferred into the polymer, is in the micrometer range and is formed by hot embossing. A silicon stamp is fabricated by mask aligner lithography and a subsequent dry etching step. An imprint template was prepared from the master and the structures are transferred into a 1 mm thick cycle-olefin polymer (COP) sheet. A subsequent sputter deposition process was carried out to form an undercut of the finger structures, which should guarantee a separation of the electrodes. A 90 nm thick gold layer was deposited by thermal evaporation to pattern the electrodes. The presented fabrication procedure represents an approach to fabricate disposable nanogap interdigitated electrode arrays allowing high signal amplifications in LoC applications. Furthermore, it demonstrates a low-cost method to fabricate IDAs with nanogaps for high volume mass production.