Light-programmed body temperature responsive glassy polymer actuators

Abstract

Temperature is a typical stimulus for polymer actuators. The use of body temperature to trigger active deformations in polymers is desirable for a vast majorities of applications. While numerous attempts have succeeded in gels and low glass transition temperatures polymers, the realization of body temperature responsive actuation in inert and rigid glassy polymers with high glass transition temperature still remains challenging.<br/> In this thesis, a novel strategy that realizes body-temperature-triggered deformations in a glassy liquid-crystalline polymer (LCP) is developed. The photo-encoded LCP exhibits fast and programmable dynamic shape morphing (in less than 1 min) upon activation. The photo-encoded deformations are not only storable for over 2 h at room temperature prior to activation, but are also erasable and rewritable without any noticeable degradation in performance. <br/> The fundamental working principles of the body temperature activation of LCP were further investigated and found closely related to the azobenzene isomerization induced thermo-mechanical property variation, evidenced by the polarized spectrometer measurements. A viscoelastic model is proposed to provide quantitatively understanding and prediction on the deformation behaviors.<br/> Based on this strategy, various self-deployed 3D structures, including tube structures, self-folded structures, inch worm structures and helical winding structures could be implemented in the LCP motifs. The deformed structures were further used to form a temperature sensitive self-formed constant force spring, a temperature selective liquid container and a time-delayed autonomous endovascular, which actively winds into a helical shape when inserted into a blood vessel.<br/>