Robot's seamless multi-material 3D liquid crystal elastomer actuator


Entirely soft robots, which are completely made of soft […]

Entirely soft robots, which are completely made of soft components, are cone winding machine of particular interests in the nascent area of soft robotics since they can provide safer human interaction, adapt to unpredictable environments, produce high specific power when actuated, and eliminate possible recurring failure compared to hybrid soft-rigid systems, presenting exceptional opportunities for various disciplines such as biomedicine, tissue engineering, and aeronautics . Stimuli-responsive materials are promising candidates for entirely soft robots because they have the potential to integrate sensors, actuators, and their control systems in the three-dimensional  soft supportive bodies .

Among all stimuli-responsive materials, liquid-crystalline elastomers  are particularly attractive owing to their extraordinary reversible shape-changing properties when exposed to various stimuli For future fabrications and applications of  robots, one critical but unaddressed issue is to integrate several components, especially multiple materials with distinctive functions, and coordinate inside the entirely soft robot body so as to carry out sophisticated operations. For instance, in robotic systems with other types of soft actuators, some require both high stiffness and low stiffness to undertake different roles . Upon integration, the soft low-stiffness parts can perform large actuation strain to change the 3D shapes on demand to passively adapt to variable environments, while the relatively rigid parts can provide high precision and generate or sustain high force to actively produce external work and complete complicated tasks.

Thus, it is substantially important to create multicomponent and multimaterial entirely soft LCE robots to improve their dexterity and flexibility and enlarge their functionalities and applications. Unfortunately, the existing  reversible  structures are almost all composed of single material due to the inherent restriction of the materials or the limitations of fabrication techniques. We emphasize that the “multicomponent” and “multimaterial” in our study refer to macroscopic heterogeneous multicomponent and multimaterial structures but not the composites that contain homogeneous or microscopically heterogeneous structures  Strictly speaking, we note that previously sporadic cases have used LCE bilayers to create heterogeneous structure .

However, for all those bilayer structures, there is a fatal problem, which is that they can only combine two different materials to make the whole structure to perform simple bending-related actuations. It is intrinsically difficult for them to realize complex multimaterial structures in which different parts can perform different actuation behaviors and exhibit different functions. Besides, the actuation type of the bilayer structures is limited to bending-related movements, which restrict their motions and prevent them from fulfilling the urgent needs of designing complex LCE robots and enlarging their future applications.

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