Article in Nature Communications

The current development of soft shape-memory materials is typically restricted to the synthesis of thin-walled samples, which greatly limits their practical application. Three-dimensional specimens can be produced using complex manufacturing methods, e.g. with additive manufacturing, but these require specialized equipment, while the production output is usually very low. M. Bobnar, N. Derets, S. Umerova, N. Novak, M. Lavrič, G. Cordoyiannis, B. Zalar and A. Rešetič, together with V. Domenici from Italy developed a new composite shape-memory material made from main-chain liquid crystal elastomer microparticles (LCEs) dispersed in a silicone polymer matrix. The composite dispersions can be effortlessly molded into arbitrary shapes or sizes, most significantly, into bulk-sized solids, which is challenging to achieve using conventional synthesis methods. Shape-memory capabilities result from temperature depended mechanical properties of the LCE inclusions. These become significantly softer at higher temperatures, when the particles reach the isotropic phase, and harden while cooled back into the glassy phase. The composite material can thus be shape-programmed by deforming the material at higher temperature and cooling it into the new stable shape, fixed by the stiffened LCE inclusions. The new shape can then be reset by heating above the isotropic phase temperature. LCE particles can be additionally magnetically ordered, providing for an additional thermomechanical reversible response. Therefore, the composite material enables efficient morphing among the virgin, thermally-programmed, and thermomechanically-controlled shapes. Together with the overall facile handling, machining and low-demanding molding production process, the newly developed composite material serves as a practical shape-morphing material for straightforward implementation into future applications, such as active elements in soft-robotics.

The results of this study were published in a paper Polymer-dispersed liquid crystal elastomers as moldable shape-programmable material in the journal Nature Communications.