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

• Applicant: Professor Dr. Rudolf Zentel
• Subject Area: Polymer Materials
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 251402731

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.

• DFG Programme: Research Grants