Changes in the mechanical properties of bioactive borophosphate fiber when immersed in aqueous solutions

Abstract

<p>Bioactive fibers have become increasingly prevalent for applications in optical sensing and as reinforcement in fully biodegradable devices. However, the typical bioactive glass fibers drawn from silicate glasses have poor mechanical properties. Here, we present our latest study on the development of new bioactive single-core (SC) borophosphate fiber with the composition (in mol%) 47.5P<sub>2</sub>O<sub>5</sub>-20CaO-20SrO-10Na<sub>2</sub>O-2.5B<sub>2</sub>O<sub>3</sub> and of core-clad (CC) borophosphate fiber, the composition (in mol%) of the clad and the core being 47.5P<sub>2</sub>O<sub>5</sub>-20CaO-20SrO-10Na<sub>2</sub>O-2.5B<sub>2</sub>O<sub>3</sub> and 0.025CeO<sub>2</sub>-0.975(47.5P<sub>2</sub>O<sub>5</sub>-20CaO-20SrO-10Na<sub>2</sub>O-2.5B<sub>2</sub>O<sub>3</sub>), respectively. We show that the immersion in aqueous solutions such as Tris(hydroxymethyl)aminomethane (TRIS) increases first the mechanical properties of the fibers due to the early congruent glass dissolution and so due to the reduction in the density of surface flaws. However, for long immersion in TRIS or in Simulated Body Fluid (SBF), the mechanical properties decrease due to the precipitation of a reactive calcium-phosphate layer at the surface of the fibers. Especially when immersed for a long time in SBF, the fibers become too fragile to allow one to measure their mechanical properties. Nonetheless, we clearly show in this study that the newly developed fibers are promising materials for reinforcing composite and/or as biosensors as these fibers still possess sufficiently high mechanical properties after immersion for significant time in SBF and/or TRIS.</p>