Nanoimprinted Plasmonic Biosensors and Biochips

In this chapter, the novel Au-capped nanopillar localized surface plasmon resonance (LSPR) chip is introduced. In the nanobiosensing field, LSPR-based sensors have attracted attention because they make it possible to perform label-free detection with high sensitivity. Moreover, a simplified optical system can be employed due to the LSPR signal being obtained at long wavelengths. Generally, electron beam exposure and etching techniques are used to make the nano-structured mold of the LSPR chip. However, these methods are very costly and time-consuming. Thus, novel fabrication methods based on the thermal nanoimprinting technique and use of porous alumina molds are introduced here. Porous alumina molds which have small or large pore size and pitch were successfully fabricated by controlling the anodizing conditions. By using thermal nanoimprinting, the nanopillar structure was transferred onto the cyclo-olefin polymer substrate from porous alumina molds. To obtain the plasmonic surface, a thin layer of gold was generated on the nanopillar structure. After optimization of the size of the alumina pores, the Au cap thickness, the diameter of the nanopillars and bovine serum albumin blocking conditions for high sensitivity detection, immunoglobulin (Ig) G/anti-IgG reactions were measured. As result, the sensitivity achieved using the Au-capped LSPR sensor was 6.7 pM antigen IgG. A noteworthy achievement of our study is the mass production of a high-density gold-based plasmon flexible chip for biosensing applications, paving the way to the commercialization of low-cost, high-sensitivity biosensors.