Liquid‐Crystalline Elastomer Fibers Prepared in a Microfluidic Device

Fleischmann, Eva‐Kristina; Forst, F. Romina; Zentel, Rudolf

doi:10.1002/macp.201400008

Cited by 34 publications

(28 citation statements)

References 40 publications

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“…Since they can be fabricated at small length scales 35,36 and powered remotely, they are ideally suited for building mobile active robots with body sizes on the scale of hundreds of microns 32 . Instead of uniformly illuminating a complex, carefullyengineered device 13 or focusing the light onto a single spot [37][38][39] , our approach is to use structured dynamic light fields to excite sophisticated intra-body deformations within LCE microrobots with very simple and agnostic designs.…”

Section: System Conceptmentioning

confidence: 99%

Structured light enables biomimetic swimming and versatile locomotion of photoresponsive soft microrobots

et al. 2016

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Microorganisms move in challenging environments by periodic changes in body shape. By contrast, current artificial microrobots cannot actively deform, exhibiting at best passive bending under external fields. Here, by taking advantage of the wireless, scalable and spatiotemporally selective capabilities that light allows, we show that soft microrobots consisting of photoactive liquid-crystal elastomers can be driven by structured monochromatic light to perform sophisticated biomimetic motions. We realized continuum yet selectively addressable artificial microswimmers that generate travelling-wave motions to self-propel without external forces or torques, as well as microrobots capable of versatile locomotion behaviours on demand. Both theoretical predictions and experimental results confirm that multiple gaits, mimicking either symplectic or antiplectic metachrony of ciliate protozoa, can be achieved with single microrobots. The principle of using structured light can be extended to other applications that require microscale actuation with sophisticated spatiotemporal coordination for advanced microrobotic technologies. 3Mobile micro-scale robots are envisioned to navigate within the human body to perform minimally invasive diagnostic or therapeutic tasks 1,2 . Biological microorganisms represent the natural inspiration for this vision. For instance, microorganisms successfully swim and move through a variety of fluids and tissues.Locomotion in this regime, where viscous forces dominate over inertia (low Reynolds number), is only possible through non-reciprocal motions demanding spatiotemporal coordination of multiple actuators 3 . A variety of biological propulsion mechanisms at different scales, from the peristalsis of annelids (Fig. 1a) to the metachrony of ciliates (Fig. 1b), are based on the common principle of travelling waves (Fig. 1c). These emerge from the distributed and self-coordinated action of many independent molecular motors 4,5 .Implementing travelling wave propulsion in an artificial device would require many discrete actuators, each individually addressed and powered in a coordinated fashion (Fig. 1d). The integration of actuators into microrobots that are mobile poses additional hurdles, since power and control need to be distributed without affecting the microrobots' mobility. Existing microscale actuators generally rely on applying external magnetic 6-10 , electric 11 , or optical 12,13 fields globally over the entire workspace. However, these approaches do not permit the spatial selectivity required to independently address individual actuators within a micro-device. Nevertheless, complex non-reciprocal motion patterns have been achieved by carefully engineering the response of different regions in a device to a spatially uniform external field 13,14 .The drawback is that this complicates the fabrication process, inhibits down-scaling and constrains the device to a single predefined behaviour. These challenges mean that most artificial microrobots actually have no actuators. Rather...

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Section: System Conceptmentioning

confidence: 99%

Structured light enables biomimetic swimming and versatile locomotion of photoresponsive soft microrobots

et al. 2016

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“…The availability of nematic monodomain μLCEs is mandatory for the design of PDLCEs. In view of the target application domain of PDLCEs, that is, moulding of macroscopically sized, thermomechanically functionalized soft objects that require abundant quantities of microparticles, recent breakthroughs in the synthesis of anisotropic colloidal μLCEs using templating 18 or microfluidics 31 32 approach offer a straightforward choice of particle production, but are technologically rather demanding as far as rapid, high-volume production is concerned. We propose a much simpler approach of low-temperature milling to freeze-fracture bulk LCE samples into micropowder with particle sizes in the 1–150 μm range (step 1 of Fig.…”

Section: Resultsmentioning

confidence: 99%

Polymer-dispersed liquid crystal elastomers

et al. 2016

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The need for mechanical manipulation during the curing of conventional liquid crystal elastomers diminishes their applicability in the field of shape-programmable soft materials and future applications in additive manufacturing. Here we report on polymer-dispersed liquid crystal elastomers, novel composite materials that eliminate this difficulty. Their thermal shape memory anisotropy is imprinted by curing in external magnetic field, providing for conventional moulding of macroscopically sized soft, thermomechanically active elastic objects of general shapes. The binary soft-soft composition of isotropic elastomer matrix, filled with freeze-fracture-fabricated, oriented liquid crystal elastomer microparticles as colloidal inclusions, allows for fine-tuning of thermal morphing behaviour. This is accomplished by adjusting the concentration, spatial distribution and orientation of microparticles or using blends of microparticles with different thermomechanical characteristics. We demonstrate that any Gaussian thermomechanical deformation mode (bend, cup, saddle, left and right twist) of a planar sample, as well as beat-like actuation, is attainable with bilayer microparticle configurations.

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“…In addition to traditional spinning processes, fibers and other structures can be generated using microfluidics. Ohm et al explored this microfluidic approach to obtain highly oriented fibers as well as microscopic beads . In the microfluidic device, the liquid crystalline, photo‐crosslinkable polyester in dichloromethane was allowed to flow through a thin capillary dispersed in a carrier fluid such as silicone oil .…”

Section: Synthesis and Alignment Of Lcesmentioning

confidence: 99%

“…Ohm et al explored this microfluidic approach to obtain highly oriented fibers as well as microscopic beads. [60][61][62] In the microfluidic device, the liquid crystalline, photo-crosslinkable polyester in dichloromethane was allowed to flow through a thin capillary dispersed in a carrier fluid such as silicone oil. 62 Due to the miscibility of the dichloromethane with silicone oil, a continuous polymer filament was formed.…”

Section: Lces Synthesized From Lc Polymersmentioning

confidence: 99%

Liquid crystal elastomer actuators: Synthesis, alignment, and applications

Kularatne

Kim

Boothby

et al. 2017

J Polym Sci B Polym Phys

273

224

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Liquid crystal elastomers (LCEs) are a unique class of materials which combine rubber elasticity with the orientational order of liquid crystals. This combination can lead to materials with unique properties such as thermal actuation, anisotropic swelling, and soft elasticity. As such, LCEs are a promising class of materials for applications requiring stimulus response. These unique features and the recent developments of the LCE chemistry and processing will be discussed in this review. First, we emphasize several different synthetic pathways in conjunction with the alignment techniques utilized to obtain monodomain LCEs. We then identify the synthesis and alignment techniques used to synthesis LCE-based composites. Finally, we discuss how these materials are used as actuators and sensors.

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Liquid‐Crystalline Elastomer Fibers Prepared in a Microfluidic Device

Cited by 34 publications

References 40 publications

Structured light enables biomimetic swimming and versatile locomotion of photoresponsive soft microrobots

Structured light enables biomimetic swimming and versatile locomotion of photoresponsive soft microrobots

Polymer-dispersed liquid crystal elastomers

Liquid crystal elastomer actuators: Synthesis, alignment, and applications

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