4D打印液晶弹性体软体机器人及其热致运动行为

4D Printed Liquid Crystal Elastomer Soft Robot and Its Thermal Derived Motion Behavior

液晶弹性体是一种交联的聚合物网络,各向异性的刚性介晶单元连接在聚合物网络中,其特殊的结构将橡胶的弹性和液晶的各向异性有机结合起来,产生特殊的光学和物理特性。通过改造基于熔融沉积技术的3D打印机,实现了液晶弹性体的精准墨水直写打印技术。在此过程中,刚性介晶单元被直接写入具有可控分子序列的三维结构中。介晶排列顺序是通过打印路径设置的,不同的排列顺序可以实现不同的刺激响应性能。基于迈克尔加成反应生成液晶大分子前驱体墨水并调控其流变性能使之可以用直径0.25 mm的细小针头挤出,并与打印参数相配合,获得形貌规整,介晶高度取向的打印样品。取向的单根液晶弹性体纤维在加热时会沿着印刷方向实现40%以上的可逆收缩。具有受控几何形状和刺激响应的结构,可以实现热致变形和无限制热致运动。除了简单的热致变形行为如弯曲、凸起和螺旋等,通过调整打印参数可以实现仿跳蚤跳动和热压弹起,以及无限制的热致滚动。这一发现使得4D打印液晶弹性体样品不再局限于简单的驱动器,而是具备智能仿生行为的软体机器人。通过4D打印批量生产的软体机器人可以实现智能仿生、运输、探索未知环境等应用。

Liquid crystal elastomer is a kind of cross-linked polymer network in which anisotropic rigid mesogenic units are connected in the polymer network.Its special structure organically combines the elasticity of rubber with the anisotropy of liquid crystal,resulting in special optical and physical properties.Through the modification of 3D printer based on melting deposition technique the accurate ink direct writing technology of liquid crystal elastomer is realized.In this process,the rigid mesogenic units are directly written into the three-dimensional structure with controllable molecular sequence.The arrangement order of mesogens is set by printing path,and different arrangement order can achieve different stimulus response performance.Based on Michael addition reaction,liquid crystal macromolecular precursor ink was prepared and its rheological properties were adjusted so that it could be extruded with a fine needle with a diameter of 0.25 mm,and the printing samples with regular morphology and highly oriented mesogens were obtained by matching with printing parameters.When heated,the aligned single LCE fiber can achieve more than 40%reversible shrinkage along the printing direction.The structure with controlled geometry and stimulus response can achieve thermal deformation and unlimited thermal motion.In addition to the simple thermal deformation behaviors such as bending,bulge,helix,etc.,the printing parameters can be adjusted to achieve flea like jumping,thermal springing and unlimited thermal rolling.This discovery makes 4D printed liquid crystal elastomer samples no longer limited to a simple driver,but a soft robot with intelligent bionic behavior.Through 4D printing mass production software robot can realize intelligent bionics,transportation,exploring unknown environment and other applications.