# Shape Memory Polyurethane and its Composites for Various Applications
## 2 Shape Memory Polyurethane in Different Applications
### Cardiovascular Implants
Figure 15: (**a**) Representative 4 mm tubular stent, (**b**) laser etched high flexible stent and details of the pattern [90]. The development of implants and its design using three-dimensional (3D) printing technique can be ground-breaking. A key advantage of 3D printing technique is that one can customize the design of object based on patient requirement. [PERSON] and [PERSON] [93] presented a novel design of bifurcated stent through the use of kirigami structures fabricated using 3D printing of SMP. The design of bifurcated stent on the basis of kirigami structure supports to produce transformable 'Y' shape from compactly folded initial shape and helps in smooth travel inside branched vein [94; 95; 96]. The shape memory was demonstrated by fixing its shape to the compact structure via shortening at above glass transition followed by cooling. The memorized structure was regained upon heating again above the glass transition temperature. They also demonstrated the bifurcated stent (Figure 17) and found increased usefulness in case of irregular forms of blood vessels. Figure 16: (**a**) Representative performance of screw (PU/PCL), (**b**) in femoral vein segment from leg of patient, (**c**) stent in stretched shape over a delivery instrument, (**d1–d2**) shape recovery step of the stent delivered in femoral vein in water at 37 \({}^{\circ}\)C [92]. Figure 17: Development of bifurcated design of tubular stent and its deployment [93]. It is known that smart devices, used for biomedical application, can be prepared using shape memory polyurethane and its composites. However, with expanding knowledge, there is a growing need for advanced technologies such as additive manufacturing or 3D printing techniques for the development of smart devices and information carriers [97; 98; 99; 100]. Several applications in the biomedical field require complex and personalized dimensions and shapes for smart devices which are difficult to produce using conventional manufacturing techniques. The combination of shape memory and 3D printing can be a solution which has enormous potential for the development of complex smart devices [98; 101; 102]. 3D printing is a low cost rapid fabrication technique with layer-by-layer additive manufacturing for the production of complex and personalized structures and devices. 3D printing of shape memory polyurethanes may need optimization of several parameters such as bulk density, dimensional accuracy, print orientation, infill percentage, surface roughness, etc., in order to produce the desired objects [103; 104]. Several researchers worldwide are trying to use additive manufacturing technique for smart device development using shape memory polyurethane and its composites. In line with this, [PERSON] et. al. [105] have developed printable PCL based photothermal shape memory polyurethane and used it as an ink for 3D printing of different shapes and structures. They demonstrated the shape memory ability of 3D printed device along with its self-healing capability. Light beam was used as an external trigger to stimulate the shape memory and self-healing. They found more than 90% shape fixing ratio and shape recovery ratio along with 70% self-healing ability. PCL and PLA based polyurethane inks are also developed by other groups who demonstrated the shape memory ability of 3D printed objects [46; 101].