Glass Scaffolds

Bioinspired Strong and Highly Porous Glass Scaffolds

Qiang Fu, Eduardo Saiz, and Antoni P. Tomsia

Oriented bioactive glass (13-93) scaffolds with controllable pore size by unidirectional freezing of camphene-based suspensions: Microstructure and mechanical response

Xin Liu, Mohamed N. Rahaman, Qiang Fu

Department of Materials Science and Engineering and Center for Bone and Tissue Repair and Regeneration, Missouri University of Science and Technology, Rolla, MO 65409, USA

Abstract

The quest for more effi cient energy-related technologies is driving the development of porous and high-performance structural materials with exceptional mechanical strength. Natural materials achieve their strength through complex hierarchical designs and anisotropic structures that are extremely difficult to replicate synthetically. We emulate nature’s design by direct-ink-write assembling of glass scaffolds with a periodic pattern, and controlled sintering of the fi laments into anisotropic constructs similar to biological materials. The final product is a porous glass scaffold with a compressive strength (136 MPa) comparable to that of cortical bone and a porosity (60%) comparable to that of trabecular bone. The strength of this porous glass scaffold is ∼ 100 times that of polymer scaffolds and 4–5 times that of ceramic and glass scaffolds with comparable porosities reported elsewhere. The ability to create both porous and strong structures opens a new avenue for fabricating scaffolds for a broad array of applications, including tissue engineering, filtration, lightweight composites, and catalyst support.

Abstract

Scaffolds of 13-93 bioactive glass (composition 6.0 Na2O, 7.9 K2O, 7.7 MgO, 22.1 CaO, 1.7 P2O5, 54.6 SiO2 (mol.%)) containing oriented pores of controllable diameter were prepared by unidirectional freezing of camphene-based suspensions (10 vol.% particles) on a cold substrate (196 C or 3 C). By varying the annealing time (0–72 h) to coarsen the camphene phase, constructs with the same porosity (86 ± 1%) but with controllable pore diameters (15–160 lm) were obtained after sublimation of the camphene. The pore diameters had a self-similar distribution that could be fitted by a diffusion-controlled coalescence model. Sintering (1 h at 690 C) was accompanied by a decrease in porosity and pore diameter, the magnitude of which depended on the pore size of the green constructs, giving scaffolds with a porosity of 20–60% and average pore diameter of 6–120 lm. The compressive stress vs. deformation response of the sintered scaffolds in the orientation directionwas linear, followed by failure. The compressive strength and elastic modulus in the orientation direction varied from 180 MPa and 25 GPa (porosity = 20%) to 16 MPa and 4 GPa (porosity = 60%), respectively, which were 2–3 times larger than the values in the direction perpendicular to the orientation. The potential use of these 13-93 bioactive glass scaffolds for the repair of large defects in load-bearing bones, such as segmental defects in long bones, is discussed. 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.