Abstract
In our work we present the complete development process of geometrically complex micro-vascular shape-memory polymer actuators. The complex geometries and three-dimensional networks are designed by means of computer aided design resources. Manufacture is accomplished, in a single step, by means of laser stereolithography, directly from the computer-aided design files with the three dimensional geometries of the different actuators under development. To our knowledge, laser stereolithography is applied here for the first time to the development of shape memory polymer devices with complex geometries and inner micro-vasculatures for their activation using a thermal fluid. Final testing of the developed actuators helps to validate the approach and to put forward some present challenges.
Highlights
Shape-memory polymers (SMPs) are active or ‘smart’ materials that present a mechanical response to external stimuli, normally changes in surrounding temperatures
For assessing the manufacturability of the inner vasculatures, and final application prototypes for testing their shape-memory properties, are obtained via additive laser stereolithography using a shape memory epoxy sold under the trade name of Accura® 60(3D Systems, 333 Three D Systems Circle, Rock Hill, SC 29730 USA) the properties of which are listed in table 1
Some studies have shown the utility of carrying out dynamic mechanical analysis for obtaining full knowledge about the properties of parts manufactured by laser stereolithography
Summary
Shape-memory polymers (SMPs) are active or ‘smart’ materials that present a mechanical response to external stimuli, normally changes in surrounding temperatures. Other types of stimuli such as light, water or chemicals, can promote shape-memory effects in polymers, we focus here on thermally activated SMPs, as they are the most common ones. When these materials are heated above their ‘activation’ temperature (Tact), typically corresponding to glass (Tg) or melting transitions (Tm), a radical stiffness change takes and the SMPs change from a rigid to an elastic state, which in some cases allows deformations of up to 400%. When the material is once again heated above its ‘activation temperature’ (normally corresponding to glass transitions temperatures) it returns to its initial non-deformed state. Among the polymers developed with remarkable shape-memory properties, the most important are epoxy resins, polyurethane resins, cross-linked polyethylene, diverse styrene-butadiene copolymers, and other formulations described in previous reports [1,2,3,4]
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