Three-Dimensional Printing of Liquid Crystal Elastomers and Their Applications

Abstract

Liquid crystal elastomers (LCEs), which are composed of liquid crystal mesogens and polymer networks, exhibit excellent actuation performance and tailorable energy dissipation behavior. They have shown great potential in practical applications in artificial muscles, soft robotics, and wearable devices. However, it is challenging to fabricate LCE samples in arbitrary three-dimensional (3D) shapes and desired alignment patterns with traditional manufacturing methods. Recently, 3D printing techniques have been introduced in combination with alignment methods of LCEs to meet this challenge. In this Review, we highlight recent advances in the 3D printing techniques of LCEs. Two kinds of printing techniques, materials extrusion and vat photopolymerization, are discussed in detail. We compare the differences and key parameters in the printing techniques, such as director fields, resolutions, and printing speeds. The applications of the printed LCE structures in soft robots, reconfigurable surfaces, and haptic devices are also introduced.

Synthesis and Characterization of a Liquid Crystal-Modified Polydimethylsiloxane Rubber with Mechanical Adaptability Based on Chain Extension in the Process of Crosslinking

“…The mechanical adaptive material is a key material in connection devices, artificial muscles, and other areas, which can effectively dissipate energy and suppress the increase of stress under continuous strain in a large deformation area. − Several attempts have been made to broaden the platform of the material’s mechanical adaptability and improve its mechanical strength. , We expect to introduce a novel energy dissipation mechanism from the molecular chain scale to further improve mechanical adaptability. Among them, liquid crystal elastomers have become the forefront of recent research due to their characteristic energy dissipation mechanism, which can undergo internal phase transition under external stimulation. − Recently, Yu et al developed 3D-printing liquid crystal elastomer foams to enhance energy dissipation under mechanical insult . Frick’s group investigated the mechanical energy dissipation behavior in polydomain nematic liquid crystal elastomers in response to oscillating loading …”

“…Among them, liquid crystal elastomers have become the forefront of recent research due to their characteristic energy dissipation mechanism, which can undergo internal phase transition under external stimulation. 9 − 14 Recently, Yu et al developed 3D-printing liquid crystal elastomer foams to enhance energy dissipation under mechanical insult. 15 Frick’s group investigated the mechanical energy dissipation behavior in polydomain nematic liquid crystal elastomers in response to oscillating loading.…”

Direct Ink Writing of Recyclable Supramolecular Soft Actuators

“…Direct ink writing (DIW) of stimuli-responsive materials is a promising microextrusion technique to create complex shapes with high resolutions, 1 which is often applied in, e.g., soft robotics, 2 − 5 haptic devices, 6 , 7 and structurally colored designs. 8 − 11 Materials applicable as inks for DIW are hydrogels, 12 , 13 shape-memory polymers, 14 , 15 and liquid crystals (LCs). 16 − 19 Among them, liquid crystal elastomers (LCEs) are attractive inks due to their large, reversible deformations and viscoelastic, non-Newtonian flow behavior.…”

“…Direct ink writing (DIW) of stimuli-responsive materials is a promising microextrusion technique to create complex shapes with high resolutions, which is often applied in, e.g., soft robotics, − haptic devices, , and structurally colored designs. − Materials applicable as inks for DIW are hydrogels, , shape-memory polymers, , and liquid crystals (LCs). − Among them, liquid crystal elastomers (LCEs) are attractive inks due to their large, reversible deformations and viscoelastic, non-Newtonian flow behavior. − The extrusion-induced shear and elongational forces result in uniaxial molecular order along the printing path direction. Generally, photoinduced cross-linking of the printed LCEs is needed as these cross-linked polymers typically show reversible shape changes around the isotropization temperature ( T i ). − …”

2022 ACS Applied Polymer Materials Early Career Forum

“…Expanding the impact of polymers toward these global challenges requires the use of materials that are easy to source and reuse, can be processed at will or on site, and provide improved performance. To this end, many investigators merge the concepts of sustainability and advanced manufacturing , with their specific polymer application. It is exciting to watch these fields, led by many of our authors here, grow and adapt to our quickly changing times.…”