Fabrication of Gold Nanodot Array for the Localized Surface Plasmon Resonance

Localized surface plasmon resonance (LSPR) is a promising method for detecting antigen-antibody binding in label-free biosensors. In this study, the fabrication of a LSPR substrate with a gold nanodot array through the lift-off process of an alumina mask is reported. The substrate showed an extinction peak in its extinction spectrum, and the peak position was dependent on the height of the gold nanodot array, and the change of extinction peak with the height could be predicted by the numerical simulation. In addition, the peak position was observed to be red-shifted with the increasing RIU value of the medium surrounding the gold nanodot array. In particular, the peak position in the 10 nm thick gold nanodot array was approximately 710 nm in air, and the sensitivity, defined as the ratio of the shift of peak position to the RIU of the medium, was 323.6 nm/RIU. The fabrication procedure could be applied to fabricate the LSPR substrates with a large area

Hydrogel-Based Capillary Flow Pumping In A Hydrophobic Microfluidic Channel

In this study, we propose a novel method to generate a capillary pressure-driven flow in a microchannel with a hydrophobic surface. The microfluidic device has a wide channel in which a hydrogel pillar array is embedded. The hydrogel pillar array was formed in the microchannel by a photopolymerization process. The flow rate due to a capillary action was strongly dependent on the distance between the pillars. Moreover, our capillary pumping with a hydrogel pillar array sustained the flow for more than 5 min with a limited sample volume. Our microfluidic device provides two advantages: (1) the modification of the polymer surface to make it hydrophilic is not required and (2) the conventional polymer molding technique can be applied to produce microfluidic devices, instead of the precision molding technique. The results indicate the possible fabrication of various microfluidic chip devices that can be easily implemented in point-of-care diagnostics. © 2014 The Japan Society of Applied Physics