Shape memory polymers in medical textiles

University of Bolton, Institute for Materials Research and Innovation, Bolton, UK 

The idea of teaching materials to remember their past or their modified physical state so that they can get back to it when an external stimuli is applied is fascinating and one that has manifested itself in shape memory materials. 

The history of these intriguing materials goes back to 1938, when A. Oleander observed the shape memory ability of An—Cd and Cu—Zn alloys (Wayman and Harrison, 1989). Later on other materials such as indium-, nickel-, titanium-, and iron-based alloys were shown to have similar behaviour (Reardon, 2011). Unlike other shape memory alloys, Ni—Ti in particular was found to be very resistant to corrosion and/or degradation and hence ideally suited to implantation in a range of applications, including the human body, albeit more expensive than its other counterparts. Hence the very first temperature-dependent shape memory alloys to be commercialised were nickel—titanium (Bogue, 2009). 

Upon application of heat, the crystal structures of such alloys begin to change from the martensitic phase into the austenite phase (Ab) until transformation is complete at Ac. Similarly, during the cooling process, the austenite phase reverts back to the 

Advances in Smart Medical Tesiiles. htlp //dx.doi.oi 0.1016/B978 l 78242-379-9.00001 3 

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