Thermo-responsive SMPs

Although SMPs show promising shape-memory effects, there are several limitations affecting their performance and desirability as follows. 1) Slow recovery speed. The rate of shape recovery process is mostly determined by the thermal conductivity of a thermo-responsive SMP. Typical SMPs have very poor thermal conductivity ( 0.3 W m 2) Low recovery stress. The... 

Shape-memory cycle of a thermo-responsive SMP. The typical shape-memory cycle of a thermo-responsive SMP consists of the following steps 1) start with a SMP in its original shape (permanent shape) 2) heat the SMP above its thermal transition temperature (Ttrans) and deform the SMP by applying an external force, cool well below 3 rans and remove the constraint to obtain the temporary shape with energy stored and 3) heat the pre-deformed SMP above Ttrans at which point the SMP releases the stored energy and recovers the permanent shape (shape recovery). Reprinted and adapted by permission from Cambridge University Press." ... 

The ability to control mechanical devices remotely by IR light with high speed and spatial precision offers many intriguing possibilities.The low recovery speed (up to several minutes) of thermo-responsive SMPs originates from their intrinsically low thermal conductivity (<0.3 W m ... 

The low recovery stress (<10 MPa) of thermo-responsive SMPs originates from their intrinsically low modulus, in the order of 0.1-1 GPa below the thermal transition temperature. CNTs have proven to enhance the mechanical properties, particularly modulus, of various polymers. ... 

Gall et al. (2005) also demonstrated the shape recovery of stent prototypes made of thermo-responsive acrylate-based SMPs at physiological temperature. And Wache et aL (2003) proposed a drug-eluting stent based on thermoplastic shape memory polyurethane showing steady drug release characteristics. 

Shape recovery in a particular SMP may be triggered by a few different stimuli. For instance, heat, water, and ethanol are all possible stimuli for polyurethanes and their composites. Additional advantages of SMPs over their metallic counterparts include high recoverable strain and easily tunable properties (http //www.azom.com/article. aspx ArticleID=6038, 13—15). Furthermore, scientific studies have also revealed that almost all polymers intrinsically have shape memory effect (SME) properties, which are also thermo- and chemo-responsive, i.e., the SME in most polymers can be either thermally activated or chemically triggered. 

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