Controllable curvature from planar polymer sheets in response to light

Hubbard, Amber M.; Mailen, Russell W.; Zikry, M. A.; Dickey, Michael D.; Genzer, Jan

doi:10.1039/c7sm00088j

Cited by 46 publications

(42 citation statements)

References 60 publications

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“…When developing stimuli‐responsive polymers and gels, researchers often demonstrate soft grippers as a potential application. Such materials have shown grasping in response to the application of various external stimuli including chemical (pH change, salt concentration, and solvent exposure), dissolution, humidity change, electrical, thermal, optical, and magnetic . Those stimuli triggered actuators exploit swelling, ion migration, oxidation, thermal expansion, phase transition, and field deformations.…”

Section: Gripping By Actuationmentioning

confidence: 99%

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Soft Robotic Grippers

et al. 2018

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Advances in soft robotics, materials science, and stretchable electronics have enabled rapid progress in soft grippers. Here, a critical overview of soft robotic grippers is presented, covering different material sets, physical principles, and device architectures. Soft gripping can be categorized into three technologies, enabling grasping by: a) actuation, b) controlled stiffness, and c) controlled adhesion. A comprehensive review of each type is presented. Compared to rigid grippers, end-effectors fabricated from flexible and soft components can often grasp or manipulate a larger variety of objects. Such grippers are an example of morphological computation, where control complexity is greatly reduced by material softness and mechanical compliance. Advanced materials and soft components, in particular silicone elastomers, shape memory materials, and active polymers and gels, are increasingly investigated for the design of lighter, simpler, and more universal grippers, using the inherent functionality of the materials. Embedding stretchable distributed sensors in or on soft grippers greatly enhances the ways in which the grippers interact with objects. Challenges for soft grippers include miniaturization, robustness, speed, integration of sensing, and control. Improved materials, processing methods, and sensing play an important role in future research.

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Section: Gripping By Actuationmentioning

confidence: 99%

“…With this operation, manipulation of 200 µm microspheres and of a several mm diameter rod were demonstrated. An interesting microgripper is shown in Figure c, which works by stimulation with infrared (IR) light . The grippers' fingers (≈10 mm length) are made of a polystyrene sheet patterned with a black ink.…”

Section: Gripping By Actuationmentioning

confidence: 99%

Soft Robotic Grippers

et al. 2018

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“…[ 8 ] Programmed buckling in response to both patterned and flood illumination has been widely exploited in gel [ 30–32 ] and shape‐memory polymer systems. [ 33–36 ] In contrast, work on liquid crystalline materials has focused primarily on the use of spatially patterned light [ 37–40 ] with a few exceptions including azobenzene‐containing LCEs with shapes blueprinted by director orientation [ 41 ] and glassy LC polymer cantilevers with coarsely patterned photothermal hinges. [ 42 ]…”

Section: Figurementioning

confidence: 99%

Blueprinting Photothermal Shape‐Morphing of Liquid Crystal Elastomers

et al. 2020

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studies have focused on programming desired 3D structures of soft materials such as shape-memory polymers [2,3] and gels [4][5][6][7] by introducing spatial variations in thermal expansion/contraction, swelling, or molecular order. [8] A particularly useful class of materials to achieve dynamic 2D to 3D shape transformations are liquid crystal elastomers (LCEs), where the coupling between the orientational ordering of polymerized mesogens and the conformation of a polymer backbone can be leveraged for large, anisotropic deformations that are dictated by the director field. [9,10] Using oriented surface alignment layers [11] or microchannels, [12] director orientation can be patterned with a resolution approaching 10 µm. [13] A subsequent reduction of nematic ordering, usually driven by heating, leads to local contraction along the director and expansion along the transverse directions, driving out-of-plane buckling into 3D shapes that are "blueprinted" by the pattern of director orientation. However, while geometric methods allow for the deduction of the necessary inplane director orientation field to generate a desired profile of Gaussian curvature, [14][15][16][17] there are a number of practical drawbacks to this approach. First, prescription of complex director fields requires significant processing, making high-throughput fabrication, and evaluation of designs challenging. Additionally, the surface alignment methods needed to specify director orientation with high spatial resolution are only amenable to certain chemistries due to the need for high mesogen content, and thus cannot be widely generalized to all LCE systems. For example, while classical LCE systems based on siloxanes, [18,19] as well as recently developed systems that rely on simple and efficient "click" chemistries, [20] offer attractive thermal and mechanical properties for shape-morphing systems, they typically only allow for alignment of the director field with coarse spatial resolution such as through application of shear stress [21][22][23] or magnetic fields. [24] To circumvent the need for a spatially varying director orientation, where the direction of deformation varies but the magnitude is constant, a potential alternative method to drive shape changes is to instead locally prescribe the magnitude of deformation within an otherwise homogeneous director field. While spatial variations in the extent of deformation have been widely employed for shape Liquid crystal elastomers (LCEs) are an attractive platform for dynamic shape-morphing due to their ability to rapidly undergo large deformations. While recent work has focused on patterning the director orientation field to achieve desired target shapes, this strategy cannot be generalized to material systems where high-resolution surface alignment is impractical. Instead of programming the local orientation of anisotropic deformation, an alternative strategy for prescribed shape-morphing by programming the magnitude of stretch ratio in a thin LCE sheet with constant director orientation is...

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“…We sought to understand why the inked regions suppress buckling since previous work suggests that light absorption by the black ink in these regions should promote localized heating. [27,28,33,34] We studied the surface morphologies of the Al/PS bilayer coated with films of inks with different mechanical and optical properties. As shown in Figure 5a, disordered island-like patterns occur beneath the black toner after IR exposure for 10 s at 90 °C.…”

Section: Resultsmentioning

confidence: 99%

Light‐Induced Buckles Localized by Polymeric Inks Printed on Bilayer Films

Park

Nallainathan

Mondal

et al. 2018

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Buckling instabilities generate microscale features in thin films in a facile manner. Buckles can form, for example, by heating a metal/polymer film stack on a rigid substrate. Thermal expansion differences of the individual layers generate compressive stress that causes the metal to buckle over the entire surface. The ability to dictate and confine the location of buckle formation can enable patterns with more than one length scale, including hierarchical patterns. Here, sacrificial "ink" patterned on top of the film stack localizes the buckles via two mechanisms. First, stiff inks suppress buckles such that only the non-inked regions buckle in response to infrared light. The metal in the non-inked regions absorbs the infrared light and thus gets sufficiently hot to induce buckles. Second, soft inks that absorb light get hot faster than the non-inked regions and promote buckling when exposed to visible light. The exposed metal in the non-inked regions reflects the light and thus never get sufficiently hot to induce buckles. This second method works on glass substrates, but not silicon substrates, due to the superior thermal insulation of glass. The patterned ink can be removed, leaving behind hierarchical patterns consisting of regions of buckles among non-buckled regions.

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Controllable curvature from planar polymer sheets in response to light

Cited by 46 publications

References 60 publications

Soft Robotic Grippers

Soft Robotic Grippers

Blueprinting Photothermal Shape‐Morphing of Liquid Crystal Elastomers

Light‐Induced Buckles Localized by Polymeric Inks Printed on Bilayer Films

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