Abstract
Integrated microfluidic devices with nanosized array electrodes and microfiltration capabilities can greatly increase sensitivity and enhance automation in immunoassay devices. In this contribution, we utilize the edge-patterning method of thin aluminum (Al) films in order to form nano- to micron-sized gaps. Evaporation of high work-function metals (i.e., Au, Ag, etc.) on these gaps, followed by Al lift-off, enables the formation of electrical uniform nanowires from low-cost, plastic-based, photomasks. By replacing Al with chromium (Cr), the formation of high resolution, custom-made photomasks that are ideal for low-cost fabrication of a plurality of array devices were realized. To demonstrate the feasibility of such Cr photomasks, SU-8 micro-pillar masters were formed and replicated into PDMS to produce micron-sized filters with 3–4 µm gaps and an aspect ratio of 3. These microfilters were capable of retaining 6 µm beads within a localized site, while allowing solvent flow. The combination of nanowire arrays and micro-pillar filtration opens new perspectives for rapid R&D screening of various microfluidic-based immunoassay geometries, where analyte pre-concentration and highly sensitive, electrochemical detection can be readily co-localized.
Highlights
Integrated microfluidic devices have shown significant promise in lowering cost and increasing automation of immunoassay detection [1,2]
We describe the use of edge-patterning method to produce nanowire-based array electrodes along with high-aspect ratio microfilters that can be both integrated within PDMS
Nanowires and nanogaps were constructed on glass substrates, which were sequentially cleaned by sonicating in aqueous suspension of Micro-90 soap, acetone, and deionized (DI) water, for 30 min each
Summary
Integrated microfluidic devices have shown significant promise in lowering cost and increasing automation of immunoassay detection [1,2]. The widths of these trenches are typically limited by the grain-size inhomogeneity of the deposited metal film [32] In this contribution, we describe the use of edge-patterning method to produce nanowire-based array electrodes along with high-aspect ratio microfilters that can be both integrated within PDMS (polydimethylsiloxane)-based microfluidics. We describe the use of edge-patterning method to produce nanowire-based array electrodes along with high-aspect ratio microfilters that can be both integrated within PDMS (polydimethylsiloxane)-based microfluidics The latter approach enables selective localization and pre-concentration of micron-sized beads at predetermined locations, which is important for electrochemical-based immunodetection [23]. The use of edge-patterning method to co-localize nanowire arrays and micro-pillar filtration opens new capabilities for the facile production of advanced microfluidic devices that could lower the cost and increase automation for electrochemical immunoassays [39]
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