Smart stent

In the endovascular aneurism repair, a stent is placed, via percutaneous pathways, inside the aneurism sac in order to exclude it fiom the systemic pressure that can lead to burst of the sac (Fig. 11.19B). Although this may be the preferred approach (when possible) and proven to be successful, it is not free from postoperative issues, namely stent displacement or endoleaks (Katzen and MacLean, 2006). It is the latter that served as a pranise for the design of a smart stent graft (Sepulveda, 2013). 

See also Smart polymers applications of, 22 355 biodegradable networks of, 22 364 cyclic and thermomechanical characterization of, 22 358—362 defined, 22 355-356 examples of, 22 362-364 molecular mechanism underlying, 22 356-358, 359t Shape-memory rings, 22 351 Shape-memory springs, in virtual two-way SMA devices, 22 346-347 Shape-memory stents, 22 352 Shape, of fiber polymers, 77 174-175. 

Fig. 7.12. a A 9.6-year-old boy with a split liver transplantation (segments II and III). The patient was admitted to the paediatric intensive care because of severe haematemesis. The fluoroscopy image shows the TIPS catheter (arrow) placed within the portal vein. Multiple collateral vessels are shown (curved arrow), b After dilation of the puncture tract, two self-expandable stents (Smart diameter 9 mm.. Cordis, Johnson Johnson Medical N.V., Belgium) were placed. Angiography shows that the collaterals have collapsed and that the primary flow direction is through the TIPS, c Measurements of intravascular pressures shows the gradient to be 8 mm Hg, well below the threshold level of 15 mm Hg... 

Need of multifunctionality and to minimise invasive surgery should contribute to the development of intelligent or smart biomaterials in future which are able to respond to light, temperature, pH, etc. In this regard, PTMC-based terpolymers with shape memory properties present great interest for potential apphcations. Moreover, the development of new processing techniques, in particular computer-assisted 3D printing, makes it possible to achieve devices or scaffolds with complex architectures such as coronary stents or atrial septal defect occluders. 

The past 10 years have been characterized by an explosion in the field of materials science. It cannot be denied that scientists all over the world exdted by the development of smart polymers, composites, and systems invest effort in studying them in potential biomedical appUcations. The term Smart defines a material or system having the ability of adapting itself to external stimulus by a number of ways, for example, shape shifting. The most known nonpolymer biomaterial is the shape memory alloys, such as NiTinol, with many dental applications [111]. Smart polymers are still under development [112, 113], some are already commercially available as in the case of smart polyurethanes (DiAPLEX ) by Mitsui Polymers. Recently, a cardiology product has been released in the market featuring smart characteristics. The discussion is about a cardiology stent dilated with the help of a balloon made from smart shape memory polyurethane as described in a 2002 US patent, and placed inside the blocked arteries of a patient [114]. 

Shape memory polymers can be laminated, coated, foamed, and even straight converted to fibers. There are many possible end uses of these smart textiles. The smart fiber made from the shape memory pol5mier can be applied as stents, and screws for holding bones together. 

There is a host of other applications for alloys displaying this effect—for example, eyeglass frames, tooth-straightening braces, collapsible antennas, greenhouse window openers, antiscald control valves on showers, women s foundation-garments, fire sprinkler valves, and biomedical applications (such as blood-clot filters, self-extending coronary stents, and bone anchors). Shape-memory alloys also fall into the classification of smart materials (Section 1.5) because they sense and respond to environmental (i.e., temperature) changes. 

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