Preparation of Janus-type actuators based on liquid crystalline elastomers in a mircrofluidic device

本项目基于近期的工作，得到了DFG （Ze 230/19）的部分支持。在此过程中，我们成功地在微流控装置中从液晶弹性体（LCEs）中制造出微米大小的颗粒，这些颗粒在温度变化（加热到相变以上）期间可逆地改变其形状。通过改变微流控装置中的参数，可以制备球形、旋转椭球或纤维形状的致动粒子，并将该制备工艺应用于不同的液晶材料。因此，驱动的类型取决于粒子内部的指向场。因此，通过改变工艺参数，从而改变引导场，可以用相同的lce材料制成膨胀或收缩的粒子。最近也出现了核-壳系统，它在驱动过程中可逆地将液体岩心泵入（或泵出）毛细管。从这一经验出发，我们打算增加lce驱动粒子的复杂性。为此，我们希望通过在微流控装置中产生致动janus型粒子来降低对称性。到目前为止，驱动粒子以对称的方式（向两边）变形。固定第二个非致动粒子（即制备janus型结构）将打破对称性并导致定向致动。这样，在一个方向上的定向运动（游泳者的准备）可能成为可能。第二步的目标是将两部分组合在一起，使其在两种不同的刺激（温度或光）下相互独立。为了实现这一目标，必须解决3个任务：首先，必须构建一个合适的微流体装置。然后(2)有必要建立两种合适的不相混的液晶聚合物体系，因为两面结构的两个部分首先都是液体状的（在交联之前），必须禁止混合。最后(3)需要开发可在微流控过程边界条件下处理的光寻址lce组件。

This project is based on recent work, which was partly supported by DFG (Ze 230/19). During it we succeeded in making micrometer sized particles from liquid crystalline elastomers (LCEs) in a microfluidic device, which change their shape reversibly during temperature variation (heating above a phase transition). It is possible to prepare the actuating particles in the shape of spheres, rotational ellipsoids or fibers by variation of the parameters in the microfluidic device and to apply the preparation process to different liquid crystalline materials. The type of actuation depends thereby on the director field inside the particle. Thus particles, which either expand or contract, can be made from the same LCE-material by varying the process parameters and thereby the director field. Very recently also core-shell systems became available, which reversibly pump the liquid core into (or out off) a capillary during the actuation process.Starting from this experience we intend to increase the complexity of the actuating particles from LCEs. For this purpose we want to reduce the symmetry by producing actuating janus-type particles in a microfluidic device. The actuating particles, made so far, deform in a symmetric way (to both sides). The fixation of a second, non actuating particle (i.e. the preparation of a janus-type structure) will break the symmetry and lead to a directed actuation. In this way a directed motion in one direction (the preparation of a swimmer) might get possible. In a second step it will be the goal to combine two parts in the janus-like structure, which actuate independent of each other as a result of two different stimuli (temperature or light). To achieve this goal 3 tasks have to be resolved: At first it will be necessary to construct a suitable microfluidic device. Then (2) it will be necessary to establish two suitable not-miscible liquid crystalline polymer systems, because both parts of the janus structure are, at first, liquid like (prior to cross linking) and a mixing must be prohibited. Finally (3) it is necessary to develop a photo-addressable LCE-component, which can be handled under the boundary conditions of the microfluidic process.