Ceramic SHaping: extrusion of glAss Preforms for new fibres in hEalthcare (SHAPE)

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Ceramic SHaping: extrusion of glAss Preforms for new fibres in hEalthcare (SHAPE)The Aim of this Project is to achieve unprecedented advances in novel glass extrusion in order to make brand new shapes of glass preforms. These preforms are needed for drawing to next-generation structured glass fibres for two targeted healthcare applications - bioimplant glass fibre for therapeutics and MIR (mid-infrared) glass fibre lasers for cancer detection.1. Glass extrusionWhat is glass extrusion? Heat glass above its glass transition temperature (Tg) and a viscous liquid forms. This liquid has treacle-like consistency and can be shaped by forcing it through a shaped metal die. For instance, a die with a hole produces a rod-shaped extrudate. The extruded rod is allowed to cool, and stiffens at Tg to form a glass-rod preform, which is taken to a draw tower and, in a separate operation, drawn to form glass fibre of the ~ diameter of a human hair. Co-extrusion, through the hole in the die, of two glass billets of different glass composition, but with matched thermal properties, forms a glass-rod preform with an internal core of different glass through it. Along part of the preform length, the internal core of glass occupies approx. constant 85 % of the diameter. When this is drawn to fibre, the fibre similarly has a large core of glass occupying 85 % of the diameter. The core/cladding interface is excellent optical quality, having mated during the extrusion itself. However, only 20% of the extruded rod preform is usable, as the core inside the rest of the preform is too tapered. Extrusion through a spider-die can produce a glass preform in the shape of a small-orificed tube. If a cane of different glass is now threaded through this tube, this whole can be drawn to fibre with a small core running through it and occupying less than ~ 20 % of the fibre diameter. Such small core fibre is vital to achieve fibre lasing. However, this processing route makes inferior optical quality core/cladding interfaces and can take several weeks.2. MIR fibreThis Project will enable straightforward manufacture of high quality small-core fibre vital for MIR-glass fibre lasers. We will extrude small-core glass-rod preforms with core less than or equal to 20 % diameter, constant over least 50 % of the preform, with core/cladding mating during extrusion to give excellent optical quality of the core/cladding interface. To achieve this breakthrough, we will invoke, for the first time, extrusion of pre-shaped glass billets, and also indirect glass extrusion - overlooked since its invention ~50 years' ago. MIR light distinguishes diseased tissue, including cancer, by detecting the molecular-makeup of the tissue. Using MIR fibre-optics will enable a new type of endoscopy so that during cancer surgery the surgeon can guide MIR fibre laser light onto the tissue and collect the reflected light to molecularly map the tissue and instantly tell if all cancer is removed. Compact MIR fibreoptic systems will be enabled by using MIR broad- and narrow-band fibre lasers; for these, small-core MIR fibre is essential and this Project will enable the new extrusion technology to make this possible. 3. Biocompatible, therapeutic fibreThe human body does not reject biocompatible fibre. We will extrude new types of multi-layered and holey biocompatible glass preforms for bioimplant fibre of finely controlled dissolution rate in the body. This is for therapeutic drug and ion release from fibre at the site of body infection and for controlled dissolution fibre-biocomposites to implant in the body to support bone-healing. 4. Project synergyThis Project will encourage cross-fertilisation of ideas, for instance a bio-compatible glass cladding for MIR glass fibres may be beneficial and using biocompatible glass fibres for NIR (near-infrared) light transmission has the potential to allow in situ monitoring of tissue health in vivo.