Plasmonic nanohole arrays with thermo-responsive hydrogel for flow-through biosensor

Optofluidics has facilitated rapid and sensitive molecule detection in real time by integrating microfluidics with optical sensing systems [1]. In the typical optofluidic device a sample is flowed over the surface that is... [ view full abstract ]

Optofluidics has facilitated rapid and sensitive molecule detection in real time by integrating microfluidics with optical sensing systems [1]. In the typical optofluidic device a sample is flowed over the surface that is functionalized with receptors specific to target analyte. In consequence, the capture of target molecules on the surface is limited by the mass transport that mainly depends on diffusion. In order to overcome mass transport limitations, perforated metallic films have been used in a flow-through format, in which the analyte solution is transported internally through the pores [2-3]. However, existing solutions such as suspended nanohole arrays rely on expensive, low throughput and time-consuming methods including focused ion beam, electron beam lithography and photolithography. These systems offer only a static design and are susceptible to the hydrodynamic deformation due to applied pressure [4]. 

In order to address these problems, we present a novel system composed of gold nanohole arrays (Au NHAs) with thermo-responsive hydrogel that accommodates array of gold nanodisks for operation in a flow-through format. The Au NHAs were fabricated on permeable substrate by accessible and cost-effective nanoimprint lithography (NIL) combined with template stripping. The nanostructures were subsequently characterized by microscopy and transmission wavelength spectroscopy. In the presented system the transport of the sample is driven by capillary forces and a hydrophilic nature of the porous substrate, improving the efficiency of target delivery to the receptor layer. Furthermore, the thermo-responsive hydrogel empowers the actuation of the optical properties by small changes around lower critical solution temperature. 

The Au NHAs presented herein offer rapid and sensitive detection of molecules and hold potential to serve as a cost-effective single-step diagnostic device.

1. Fan, Xudong, and Ian M. White. "Optofluidic microsystems for chemical and biological analysis." Nature photonics 5.10 (2011): 591-597
2. Eftekhari, Fatemeh, et al. "Nanoholes as nanochannels: flow-through plasmonic sensing." Analytical chemistry 81.11 (2009): 4308-4311
3. Yanik, Ahmet Ali, et al. "Integrated nanoplasmonic-nanofluidic biosensors with targeted delivery of analytes." Applied physics letters 96.2 (2010): 021101.
4. Tu, Long, et al. "Study of flow rate induced measurement error in flow-through nano-hole plasmonic sensor." Biomicrofluidics 9.6 (2015): 064111