A Time-Efficient Dip Coating Technique for the Deposition of Microgels onto the Optical Fiber Tip

Lorenzo Scherino,Armando Ricciardi,Vera La Ferrara,Alberto Micco,Martino Giaquinto,Anna Aliberti,Eugenia Bobeico,Menotti Ruvo,Andrea Cusano

doi:10.3390/fib6040072

Abstract

The combination of responsive microgels and Lab-on-Fiber devices represents a valuable technological tool for developing advanced optrodes, especially useful for biomedical applications. Recently, we have reported on a fabrication method, based on the dip coating technique, for creating a microgels monolayer in a controlled fashion onto the fiber tip. In the wake of these results, with a view towards industrial applications, here we carefully analyze, by means of both morphological and optical characterizations, the effect of each fabrication step (fiber dipping, rinsing, and drying) on the microgels film properties. Interestingly, we demonstrate that it is possible to significantly reduce the duration (from 960 min to 31 min) and the complexity of the fabrication procedure, without compromising the quality of the microgels film at all. Repeatability studies are carried out to confirm the validity of the optimized deposition procedure. Moreover, the new procedure is successfully applied to different kinds of substrates (patterned gold and bare optical fiber glass), demonstrating the generality of our findings. Overall, the results presented in this work offer the possibility to improve of a factor ~30 the fabrication throughput of microgels-assisted optical fiber probes, thus enabling their possible exploitation in industrial applications.

Highlights

Integrating onto the optical fiber tip resonant nanostructures able to trap light at specific wavelengths is at the base of the Lab-on-Fiber (LOF) technology [1,2,3,4,5,6]
We have reported a reliable fabrication strategy, based on the dip coating technique, for realizing, in a controlled fashion, monolayers of MGs onto the optical fiber tip [11]
We have demonstrated that coverage factor (CF) larger than 90% warranted the maximum degree of light-MGs interactions onto the fiber tip, and the maximum responsivity to MGs swelling/collapsing induced by the specific external stimulus of interest [11,12]

Summary

Introduction

Integrating onto the optical fiber tip resonant nanostructures able to trap light at specific wavelengths is at the base of the Lab-on-Fiber (LOF) technology [1,2,3,4,5,6]. The resulting electromagnetic field confinement at sub-wavelength scale strongly enhances the light matter interaction, making possible to detect environmental changes onto the fiber surface as resonance wavelength shifts and/or intensity variation of the optical signal coupled to the fiber [4,5]. In this manner, ultra-sensitive optrodes based on LOF technology have been developed and exploited in biochemical applications, i.e., for detecting the presence of nano-sized bio-coating film resulting from molecular interactions.

Methods

Results

Conclusion