Responding to external stimuli is a trait observed in all living organisms. Modern artificial materials have adopted this profound characteristic, thereby commencing the field of stimuli-responsive systems. Liquid crystal polymers are attractive members of this family of systems owing to the available control on their anisotropic properties capable of generating complex morphologies under external stimuli. Liquid crystal polymer systems have been designed to respond to various stimuli such as heat, light, pH, humidity, and electric and magnetic fields. The attainable shapes and topographies open exciting possibilities for novel applications in a wide range of different fields such as microfluidics, artificial muscles, haptics, and optical functions. The microstructural design of liquid crystal polymers leading to diverse applications is the focus of this review. We conclude by presenting the future prospects and developments in these promising material systems.

Tight bending bio-inspired soft actuators were fashioned in liquid crystalline networks by using a novel tapered film geometry.

Soft actuators allowing multifunctional, multishape deformations based on single polymer films or bilayers remain challenging to produce. In this contribution, direct ink writing is used for generating patterned actuators, which are in between single- and bilayer films, with multifunctionality and a plurality of possible shape changes in a single object. The key is to use the controlled deposition of a light-responsive liquid crystal ink with direct ink writing to partially cover a foil at strategic locations. We found patterned films with 40% coverage of the passive substrate by an active material outperformed “standard” fully covered bilayers. By patterning the film as two stripes, a range of motions, including left- and right-handed twisting and bending in orthogonal directions, could be controllably induced in the same actuator. The partial coverage also left space for applying liquid crystal inks with other functionalities, exemplified by fabricating a light-responsive green reflective actuator whose reflection can be switched “on” and “off”. The results presented here serve as a toolbox for the design and fabrication of patterned actuators with dramatically expanded shape deformation and functionality capabilities.

Liquid crystalline networks of specific geometry are observed to undergo thermally triggered chaotic continual rocking motion and light triggered rolling.

Achieving oscillatory motion in polymers without requiring on/off switching of stimuli is a current challenge. Hereby, a free‐standing liquid crystal polymer (LCP) is demonstrated to undergo a sustained oscillatory motion when triggered by light, moving back and forth, resembling the motion of a rocking‐chair. Two polymer films having different azobenzene photo‐switches have been studied, revealing photoswitch requirements as well as illumination conditions necessary to sustain oscillations. The motion presented here shows how feedback loops involving light‐triggered actuation, self‐shadowing and a shifting center of gravity can be utilized to achieve self‐sustained motion in free‐standing polymers.