Shape Memory Materials for Biomedical Applications

Abstract

Shape memory properties provide a very attractive insight into materials science, opening unexplored horizons and giving access to unconventional functions in every material class (metals, polymers, and ceramics). In this regard, the biomedical field, forever in search of materials that display unconventional properties able to satisfy the severe specifications required by their implantation, is now showing great interest in shape memory materials, whose mechanical properties make them extremely attractive for many biomedical applications. However, their biocompatibility, particularly for long‐term and permanent applications, has not yet been fully established and is therefore the object of controversy. On the other hand, shape memory polymers (SMPs) show promise, although thus far, their biomedical applications have been limited to the exploration. This paper will first review the most common biomedical applications of shape memory alloys and SMPs and address their critical biocompatibility concerns. Finally, some engineering implications of their use as biomaterials will be examined.

Mechanisms of the Shape Memory Effect in Polymeric Materials

“…On the other hand, a few new shape memory phenomena have been discovered [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47], which not only enhance the flexibility of the current shape memory technology, but also add in new dimensions for extended versatility and adoptability. Consequently, a number of novel concepts have been proposed for a range of engineering applications [45,[48][49][50][51][52][53][54], in particular in the field of biomedical engineering as of the last couple of years [24,43,[55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70].…”

Ternary β and γ phases in the Al–Au–Cu system at 750°C

“…This trend suggests a formula Al 4 Au x Cu 9-x for the γ-phase in this system, with a lattice parameter of 0.8704 nm for Al 4 Au 0 Cu 9 , increasing to 0.9175 for Al 4 Au 5.3 Cu 3.7 . Samples 1, 2 and 5 also shared very similar characteristics, being extremely brittle and silver-white in colour.…”

“…This has enabled a wide range of uses for these materials, with applications ranging from under-wires of bras to arterial stents and intricate jewellery [2][3][4][5][6]. However, there are some limitations due to the fact that many SMAs suffer from aging and martensite stabilization [7][8][9].…”

Three-dimensional constitutive model for shape memory polymers using multiplicative decomposition of the deformation gradient and shape memory strains

“…Two-way shape memory, i.e., reversible deformation behavior in response to an on-off stimulus, has also been demonstrated using one-way SMPs and bias loads (Chung et al, 2007;Hong et al, 2010;Pandini et al, 2012). Due to these fascinating properties, SMPs are promising for use in many applications, including aerospace devices , self-healing medical materials (Li and Shojaei, 2012;Xu and Li, 2010), smart biomedical stents (El Feninat et al, 2002;Kim et al, 2010a;Reese et al, 2010), fiber-reinforced SMP composites (Lan et al, 2014;Tan et al, 2014;Zhang et al, 2015), particle-reinforced SMP composites (Hong et al, 2008), metal-SMP composites (Wang and Li, 2011), Alloy-SMP composite (Qiao et al, 2013), and 4D printings (Ge et al, 2014;Ge et al, 2013;Yu et al, 2015).…”