Microstructured Optical Waveguide-Based Endoscopic Probe Coated with Silica Submicron Particles

Abstract

Microstructured optical waveguides (MOW) are of great interest for chemical and biological sensing. Due to the high overlap between a guiding light mode and an analyte filling of one or several fiber capillaries, such systems are able to provide strong sensitivity with respect to variations in the refractive index and the thickness of filling materials. Here, we introduce a novel type of functionalized MOWs whose capillaries are coated by a layer-by-layer (LBL) approach, enabling the alternate deposition of silica particles (SiO2) at different diameters—300 nm, 420 nm, and 900 nm—and layers of poly(diallyldimethylammonium chloride) (PDDA). We demonstrate up to three covering bilayers consisting of 300-nm silica particles. Modifications in the MOW transmission spectrum induced by coating are measured and analyzed. The proposed technique of MOW functionalization allows one to reach novel sensing capabilities, including an increase in the effective sensing area and the provision of a convenient scaffold for the attachment of long molecules such as proteins.

Functionalized Microstructured Optical Fibers: Materials, Methods, Applications

“…The proximity of the hollow channels surrounding the central solid-core of the suspended-core MOFs enables a strong overlap of the light guided mode and any material filled inside. The major advantage of using hollow-core MOFs rather than other techniques based on geometry-modified optical fibers, cuvettes, and bulk optics, lies in combining the long interaction lengths with strong overlapping between the light mode, that penetrates deeply into the air capillaries via its evanescent field, and the injected analyte [16]. More practical approaches of using the accessibility of the air capillaries for the functionalization of the MOF surface were shown by Sukhishvili S. et al on the example of solid and hollow-core MOFs [50,63] (Figure 3a,c).…”

“…The further development of MOF-based sensors gave rise to a new research direction for the tuning of optical properties. Various approaches have been proposed and realized for MOF modification [77]; different solid [15,16,[78][79][80][81] and liquid materials [82] were injected into the fiber hollow regions. Among others, one can highlight such well-described approaches for the injection of host materials such as pressure-assisted melt filling ( Figure 12) [79], chemical vapor deposition [83], and direct fiber drawing [77].…”

“…Recently, the technique of polyelectrolyte LBL deposition, originally applied for the preparation of nanofilms [13,58] and later used for the formation of microcapsules [91][92][93][94], as well as the functionalization of planar surfaces [95], have been adapted for the surface modification of optical fibers [96]. These can either be buffer layers [15,16] with a controlled value of surface potential for better particle adsorption or the sensitive layers by themselves [97]. A nanoscale thickness accuracy is possible by varying a set of parameters such as, among others polyelectrolyte concentration, adsorption time, ionic strength, solvent composition, and temperature [58].…”

“…Based on a similar approach of host materials deposition inside MOF samples, we reported a novel type of functionalized MOF sample whose capillaries were coated with silica submicron particles (SiO 2 ) with different diameters (300, 420, and 900 nm) and layers of poly(diallyldimethylammonium chloride). We also recently demonstrated the possibility of multilayer deposition on the example of silica particles at a diameter of 300 nm (Figure 13) [16]. This modification technique of MOFs allows one to reach novel sensing capabilities, which benefit from an increased effective sensing area and the provision of a convenient scaffold for the binding of specific molecules [14].…”

“…In this work, we review the various types of functionalization techniques of MOFs that have enabled the improvement of their performance and have created new perspectives for the use of cases of plasmonic nanoparticles and metal nanowires. The novel technique of layer-by-layer (LBL) [13] deposition, previously used mainly for the deposition of thin films onto planar substrates and adapted for the functionalization of fiber surfaces, in order to make the attachment of target molecules or particles possible, or for the creation of areas sensitive to a specific medium, is also considered [14][15][16]. This review concentrates on the different methods used for the modifications of optical fibers and highlights the novel functionalities which go beyond the manipulation of transmitted light, revealing the innovative applications of these structures, rather than investigating the origins of the underlying physical phenomena.…”