<P> Shape - memory polymers differ from shape memory alloys (SMAs) by their glass transition or melting transition from a hard to a soft phase which is responsible for the shape - memory effect . In shape - memory alloys martensitic / austenitic transitions are responsible for the shape - memory effect . There are numerous advantages that make SMPs more attractive than shape memory alloys . They have a high capacity for elastic deformation (up to 200% in most cases), much lower cost, lower density, a broad range of application temperatures which can be tailored, easy processing, potential biocompatibility and biodegradability, and probably exhibit superior mechanical properties than SMAs . </P> <P> One of the first conceived industrial applications was in robotics where shape - memory (SM) foams were used to provide initial soft pretension in gripping . These SM foams could be subsequently hardened by cooling making a shape adaptive grip . Since this time the materials have seen widespread usage in e.g. the building industry (foam which expands with warmth to seal window frames), sports wear (helmets, judo and karate suits) and in some cases with thermochromic additives for ease of thermal profile observation . Polyurethane SMPs are also applied as an autochoke element for engines . </P> <P> One fascinating field in which SMPs are impacting quite significantly nowadays is photonics . Due to the shape changing capability, SMPs enable the production of functional and responsive photonic gratings . In fact, by using modern soft lithography techniques such as replica molding, it is possible to imprint periodic nanostructures, with sizes of the order of magnitude of visible light, onto the surface of shape memory polymeric blocks . As a result of the refractive index periodicity, these systems diffract light . Interestingly, by taking advantage of the polymer's shape memory effect, it is possible to reprogram the lattice parameter of the structure and consequently tune its diffractive behavior . Another application example of SMPs in photonics is in shape changing random lasers . By doping SMPs with highly scattering particles such as titania ones it is possible to tune the light transport properties of the composite . Additionally, optical gain may be introduced by adding a molecular dye to the material . By configuring both the amount of scatters and of the organic dye, a light amplification regime may be observed when the composites are optically pumped . </P> <P> Most medical applications of SMP have yet to be developed, but devices with SMP are now beginning to hit the market . Recently, this technology has expanded to applications in orthopedic surgery . Additionally, SMPs are now being used in various ophthalmic devices including punctal plugs, glaucoma shunts and introacular lenses . </P>

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