Discrete-state photomechanical actuators

Skandani, A. Alipour; Chatterjee, Sourav; Smith, Matthew L.; Baranski, John; Wang, David H.; Tan, Loon‐Seng; White, Timothy J.; Shankar, M. Ravi

doi:10.1016/j.eml.2016.05.002

Cited by 14 publications

(8 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Intersnap times range from 1.2 to 11.8 seconds, with an average time of 3.8 seconds. While oscillation due to self‐shadowing effects [ 37,42,57–59 ] and snapping between two bistable shapes [ 60,61 ] has been reported previously in nematic beams, cyclic oscillation via photoinduced snapping has only been reported in one other case, [ 62 ] to our knowledge. We hypothesize that this phenomenon is driven by self‐shadowing, where slight changes in the incident light intensity due to deformation toggles the equilibrium between buckling modes.…”

Section: Figurementioning

confidence: 93%

Blueprinting Photothermal Shape‐Morphing of Liquid Crystal Elastomers

et al. 2020

View full text Add to dashboard Cite

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...

show abstract

Section: Figurementioning

confidence: 93%

Blueprinting Photothermal Shape‐Morphing of Liquid Crystal Elastomers

et al. 2020

View full text Add to dashboard Cite

show abstract

“…We remark that, in deriving the equations, we assumed that the material response-the relation between curvature and moment [6], and the relation between illumination and spontaneous curvature [7]-are linear. Yet, the final equations are nonlinear, as evidenced by the presence of the trigonometric terms in [12] and f in [13] due to the presence of finite rotations.…”

Section: Photodeformable Elasticamentioning

confidence: 99%

“…The critical event in the emergence of wavelike cyclic behavior is the snap-through instability. We study this instability more closely in our final example, by analyzing the experiments first conducted by Shankar and coworkers (12,13).…”

Section: Snap-through Instability Of Doubly Clamped Beamsmentioning

confidence: 99%

A nonlinear beam model of photomotile structures

Korner

Kuenstler

Hayward

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Actuation remains a significant challenge in soft robotics. Actuation by light has important advantages: Objects can be actuated from a distance, distinct frequencies can be used to actuate and control distinct modes with minimal interference, and significant power can be transmitted over long distances through corrosion-free, lightweight fiber optic cables. Photochemical processes that directly convert photons to configurational changes are particularly attractive for actuation. Various works have reported light-induced actuation with liquid crystal elastomers combined with azobenzene photochromes. We present a simple modeling framework and a series of examples that study actuation by light. Of particular interest is the generation of cyclic or periodic motion under steady illumination. We show that this emerges as a result of a coupling between light absorption and deformation. As the structure absorbs light and deforms, the conditions of illumination change, and this, in turn, changes the nature of further deformation. This coupling can be exploited in either closed structures or with structural instabilities to generate cyclic motion.

show abstract

“…The performances of these stations and of the microfactory are strongly dependent on the characteristics of these micro-positioning devices such as the production rate, flexibility, precision, and energy consumption. Different architectures of micro-positioning devices can be found in the literature and can be classified according to their architecture, either long-range actuators [1][2][3][4][5] or on an array of shortrange actuators [6][7][8][9][10]. Positioning with the help of long-range actuators is mostly carried out using the analogical principle due to their high precision and good position repeatability.…”

Section: Introductionmentioning

confidence: 99%

Planar Micro-Positioning Device Based on a 3D Digital Electromagnetic Actuator

et al. 2021

View full text Add to dashboard Cite

In this paper, a novel micro-positioning device based on a 3D digital actuator is presented. The proposed system allows realizing planar motions of micro-objects, which could be implemented in several applications where micro-positioning tasks are needed such as micro-component manufacturing/assembly, biomedicine, scanning microscopy, etc. The device has three degrees of freedom, and it is able to achieve planar motions of a mobile plate in the xy-plane at two different levels along the z-axis. It consists of a hexagonal mobile part composed of a permanent magnet that can reach twelve discrete positions distributed between two z-axis levels (six at each level). Two different approaches are presented to perform positioning tasks of the plate using the digital actuator: the stick-slip and the lift-mode approaches. A comparison between these two approaches is provided on the basis of the plate displacement with respect to different current values and conveyed mass. It was observed that for a current of 2 A, the actuator is able to displace a mass of 1.15 g over a distance of 0.08 mm. The optimal positioning range of the planar device was found to be ±5.40 mm and ±7.05 mm along the x- and y-axis, respectively.

show abstract

Discrete-state photomechanical actuators

Cited by 14 publications

References 22 publications

Blueprinting Photothermal Shape‐Morphing of Liquid Crystal Elastomers

Blueprinting Photothermal Shape‐Morphing of Liquid Crystal Elastomers

A nonlinear beam model of photomotile structures

Planar Micro-Positioning Device Based on a 3D Digital Electromagnetic Actuator

Contact Info

Product

Resources

About