Toward the fabrication of extruded microstructured bioresorbable phosphate glass optical fibers

Abstract

The steps toward the fabrication of directly extruded microstructured fiber preforms made of a bioresorbable phosphate glass are herein presented, analyzing the features of the process from the glass synthesis to the manufacturing of the fiber. The realization of these fibers leverages on three main pillars: an optically transparent bioresorbable glass, its extrusion into a preform, and the fiber drawing. The glass has been designed and carefully prepared in our laboratory to be dissolvable in a biological fluid while being optically transparent and suitable for both preform extrusion and fiber drawing. To support the production of an optimized die for the preform extrusion, a simplified laminar flow model simulation has been employed. This model is intended as a tool for a fast and reliable way to catch the complex behavior of glass flow during each extrusion and can be regarded as an effective design guide for the dies to fulfill the specific needs for preform fabrication. After die optimization, extrusion of a capillary was realized, and a stacking of extruded tubes was drawn to produce a microstructured optical fiber made of bioresorbable phosphate glass.

Microstructured Optical Fiber Made From Biodegradable and Biocompatible Poly(D,L-Lactic Acid) (PDLLA)

“…7 shows the cross-section of the end-facet of mbioPOF M2b, with an elliptical shape and a major axis of around 132 µm, and clearly demonstrates the modal field confinement in the core of the fiber. Whilst light guidance has previously been shown in a structured yet incompletely characterized bioresorbable phosphate glass-based fiber [25] and in a structured agarosebased fiber [11] with feature sizes in the millimeter range, our results represent the first demonstration ever of microstructurebased light guidance in commercially available and synthetic polymer-based fully-fledged microstructured optical fiber.…”

“…The optical characteristics of these microstructured fibers, however, were not reported. Note that bioresorbable phosphate glass was also used for manufacturing microstructured fibers using a stack-and-draw technique [25]. Structured preforms were prepared by stacking extruded capillaries within a tube, and were then heat-drawn into a fiber [30].…”

Lighting the Path: Light Delivery Strategies to Activate Photoresponsive Biomaterials In Vivo

“…Extrusion can be applied to meltable and chemically‐ or physically‐curable materials provided that the structural locking of the waveguide form—for example, through cooling below T g or crosslinking—can be rapidly induced immediately after extrusion (Figure 8e). Extrusion has also been used for producing complex pre‐forms, for example oversized hollow‐channel pre‐forms of resorbable glasses, [ 157 ] that then undergo thermal drawing to generate the final waveguide. Our workgroup recently used extrusion‐based printing processes to produce degradable polyester waveguides extruded from the melt, [ 121 ] and degradable PEG‐based hydrogel waveguides [ 158 ] and non‐degradable PDMS‐based elastomeric waveguides cured by in situ photocrosslinking.…”

Challenges in the Fabrication of Biodegradable and Implantable Optical Fibers for Biomedical Applications

“…Instead, PGs processing allows for preform fabrication by means of a rod-in-tube technique. D. Gallichi-Nottiani and D. Pugliese et al [ 61 ] recently demonstrated the fabrication of microstructured fiber preforms of bioresorbable phosphate glass and subsequent fiber drawing. To form this complex preform, the authors first obtained the outer tube by direct extrusion and subsequently they used a standard stack-and-draw technique [ 47 ], for which the preform was prepared by stacking the extruded capillaries within a tube.…”

“…PG-based fibers demonstrated the potential to be fabricated with a small diameter, yielding single mode guidance. They also allow for microstructuring [ 61 ] and for the inscription of fiber Bragg gratings (FBG) [ 59 ], which are well-known fiber-based sensor elements that allow projecting advanced biosensing applications. One still needs to account for the fragility of PG-based fibers.…”