Liquid Crystal Templates Combined with Photolithography Enable Synthesis of Chiral Twisted Polymeric Microparticles

Akdeniz, Burak; Büküşoğlu, Emre

doi:10.1002/marc.201970035

Cited by 5 publications

(11 citation statements)

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“…Anisotropic shrinkage is one of the parameters to determine the final shape of the microparticles. Previously, we have shown that the shrinkage changes almost linearly from 65.6 ± 2.7% to 45.7 ± 3.5% perpendicular to the LC director when the monomer content of the mixture was changed from 10 to 30 wt % and remains almost constant at around 10.5 ± 2.4% parallel to the nematic director . We show here how predictive the shrinkage extends was in determining the final shapes of the microparticles.…”

Section: Resultssupporting

confidence: 52%

“…The alignments of the LCs, which were indicated on the left side of the figure, were maintained by either rubbed-PVA-coated surfaces for uniform planar or DMOAP-functionalized surfaces for uniform homeotropic anchoring inside the film. After extraction of the unreacted part, the microparticles maintained their final shapes due to the anisotropic shrinkage, which we had shown to be more substantial in a direction perpendicular to the LC director . In the end, considering the shape symmetry of the microparticles and the anisotropy of the shrinkage, we were able to synthesize microparticles with 22 different shapes using 6 different masks and uniform LC alignment with four different directions within the films as shown in Figure .…”

Section: Resultsmentioning

confidence: 93%

“…We have shown a potential for a control over the chirality and the pitch size of the chiral twisted microparticles with our synthesis method . Herein, we show how precisely this could be achieved by performing measurements on the chiral twisted microparticles.…”

Section: Resultsmentioning

confidence: 94%

“…This is a relatively small thickness of a film such that the LC anchoring at the two sides of the films may deviate from the rubbing direction of the surfaces. To check this, we made measurements of the LC twist angles within the film and found that they were indeed the angles set by the contacting surfaces (Figure S3 and ref ). Next, we questioned whether the chiral twist in the molecular alignment within the film after polymerization was different than the twist initially set by the LC director profile.…”

Section: Resultsmentioning

confidence: 98%

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Design Parameters and Principles of Liquid-Crystal-Templated Synthesis of Polymeric Materials via Photolithography

Akdeniz

Büküşoğlu

2019

Langmuir

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The design parameters and principles for the synthesis of polymeric microscopic objects using a method that combines photolithography and liquid crystal (LC) molecular templates have been demonstrated. Specifically, mixtures of a reactive mesogen (RM257) and nonreactive LC (E7) were polymerized using UV light and a photomask. We used photomasks with circular, triangular, rectangular, square, star-shaped, and heart-shaped features to provide initial shapes to the objects. Then, the unreacted parts were extracted and the polymeric objects were allowed to shrink anisotropically as defined by the ordering symmetry of the LC mixture. The initial configuration of the LC mixtures played a critical role in determining the final shapes of the polymeric objects formed after shrinking, which resulted in chiral twisting and bending, leading to more than 20 different shapes. We found that the pitch size of the bulk chiral twisted objects depends linearly on the angle of chiral twist of the LCs, whereas it was independent of their thickness and length ranging from 1.5 to 160 μm and 100 μm to 2.45 cm, respectively. The shapes of the polymeric objects synthesized from LC films with bent LC ordering, however, were critically dependent on the thickness of the objects due to the interplay between the elastic energy and surface anchoring of the LCs. The critical role of LC elasticity was observed for thicknesses below 20 μm, above which surface anchoring was dominant in determining the shapes. Overall, the proposed method was shown to provide a precise control over the three-dimensional architectures of the objects with size range that covers the micro and macro scales, which would find use in fields ranging from emulsion stabilization and catalysis to micromachines and artificial muscles.

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Section: Resultssupporting

confidence: 52%

Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 98%

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Design Parameters and Principles of Liquid-Crystal-Templated Synthesis of Polymeric Materials via Photolithography

Akdeniz

Büküşoğlu

2019

Langmuir

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“…Furthermore, a complicated pattern of molecular distribution is needed for the 3D complex deformation. 3D printing [72,73,74] and lithography [75,76] are examples of technologies developed to create 3D polymer structures with sophisticated control over deformation. Moving beyond simple, light-driven motion of soft robots, the main difficulty is how to generate and regulate multiple shapes in a single robot.…”

Section: Liquid Crystalline Polymersmentioning

confidence: 99%

Contactless Manipulation of Soft Robots

et al. 2019

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In recent years, jointless soft robots have demonstrated various curvilinear motions unlike conventional robotic systems requiring complex mechanical joints and electrical design principles. The materials employed to construct soft robots are mainly programmable anisotropic polymeric materials to achieve contactless manipulation of miniaturized and lightweight soft robots through their anisotropic strain responsivity to external stimuli. Although reviews on soft actuators are extensive, those on untethered soft robots are scant. In this study, we focus on the recent progress in the manipulation of untethered soft robots upon receiving external stimuli such as magnetic fields, light, humidity, and organic solvents. For each external stimulus, we provide an overview of the working principles along with the characteristics of programmable anisotropic materials and polymeric composites used in soft robotic systems. In addition, potential applications for untethered soft robots are discussed based on the physicochemical properties of programmable anisotropic materials for the given external stimuli.

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Shape Morphing Directed by Spatially Encoded, Dually Responsive Liquid Crystalline Elastomer Micro‐Actuators

et al. 2022

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have been developed to control the inplane director field, including mechanically stretching/shearing, [23][24][25] guiding by surface patterns, [16,[26][27][28] and use of electric or magnetic field. [29] Out-of-plane bending of a flat LCE film can be realized when there is a gradient in the director field induced by different surface anchoring on top and bottom of the film [30,31] or in mechanical properties along the film thickness. [32][33][34] So far few have shown control of both in-plane and out-of-plane orientations of LC mesogens with complex director fields in the 3D space, locally and globally. Using a top and bottom substrate with planar microchannels oriented in different directions has shown such potentials. [28] However, the thickness of films (up to 100 µm) is limited by the decreasing molecular interactions away from the surface, causing deviation of the mesogens from the aligned direction along film depth. 3D printing allows for arbitrary arrangement of mesogens in 3D space, however, the printing resolution is typically on the order of hundreds of micrometers to millimeters. Thus, only simple geometries are printed, and it is time consuming to build layer-by-layer. While the intrinsic anisotropy of LC mesogens enables reversible actuation, it also constrains the choice of materials, fabrication, and spatial control of the shape morphing, due to the coupling between these aspects.Incorporating LCEs with other materials provides a feasible pathway to expand the materials library for shape morphing. A bilayer-structure of LCE and hydrogel with different elasticity has been demonstrated. [35,36] However, a strong bonding between the two layers is essential, otherwise, it will lead to a small strain [35] and poor reversibility. [36] Microparticles made by freeze-milling the bulk LCE film have been embedded in a conventional elastomer, polydimethylsiloxane (PDMS), followed by alignment under an external magnetic field to create macroscopic "monodomains" for actuation. [37] The use of discrete microparticles allows for decoupling of the enabling components [38] from the matrix itself. Nevertheless, those microparticles are not uniform in size nor anisotropic in shape. They are only aligned along an in-plane direction and a bilayer structure is still needed to achieve out-of-plane bending. Furthermore, the magnetic field-induced mesogen alignment is mostly limited to side-chain LC monomers due to high viscosity of mainchain system. Main-chain LCE microparticles [39][40][41][42][43][44] (Young's modulus E, ≈ 10's MPa) or side-chain LCE micro-actuators [45,46] Liquid crystalline elastomers (LCEs) with intrinsic molecular anisotropy can be programmed to morph shapes under external stimuli. However, it is difficult to program the position and orientation of individual mesogenic units separately and locally, whether in-plane or out-of-plane, since each mesogen is linked to adjacent ones through the covalently bonded polymer chains. Here, dually responsive, spindle-shaped micro-actuators are synthesized from ...

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Liquid Crystal Templates Combined with Photolithography Enable Synthesis of Chiral Twisted Polymeric Microparticles

Cited by 5 publications

References 0 publications

Design Parameters and Principles of Liquid-Crystal-Templated Synthesis of Polymeric Materials via Photolithography

Design Parameters and Principles of Liquid-Crystal-Templated Synthesis of Polymeric Materials via Photolithography

Contactless Manipulation of Soft Robots

Shape Morphing Directed by Spatially Encoded, Dually Responsive Liquid Crystalline Elastomer Micro‐Actuators

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