Nature is replete with examples of biological structures that exhibit unusual mechanical properties. The high mechanical strength of mollusk shells, abrasion resistance of human teeth and toughness of bones are examples of mechanical properties that remain unrivalled by most engineered materials made so far. Interestingly, these mechanical properties in the natural materials arise from their internal structures comprising periodically arranged complex mineral-organic structures. For instance, mollusk shells have a “brick-mortar” like arrangement of hard CaCO3 platelets within a relatively softer organic matrix.
These distinctive bio-inspired designs can serve as an inspiration for the development of advanced light-weight composites. Moreover, if these composites could be made using biocompatible materials, they could find applications in biomedical implants and several other biomedical applications. The challenge, though, is to develop such composites with complex (hierarchical) mineral-organic interfaces.
Herein, we report the development of a bio-inspired composite with a distinctive “interlocked” mineral-organic interface across each layer of the composite. This is achieved through a unique biomineralization strategy involving growth of aragonite crystals with repeating micro-textures on their surface. The mineralization process is optimized to induce growth of such micro-textured aragonite mineral platelets with greater uniformity over arbitrarily large-area. Subsequently, an approach to bond these mineralized platelets layer-by-layer, to develop the bio-inspired composite (with interlocked interfaces) is discussed. It is found that the bio-inspired composite with the “interlocked” mineral-organic interfaces exhibits nearly twice the tensile strength as that of the composite without the interlocking. Moreover, the former exhibits a stiffness of 15-20 GPa which is comparable to the stiffness of the natural bone. Owing to the analogous composition of the composites as that of the biological nacre, the former exhibits biocompatibility as evidenced by in-vitro cell viability tests.