Hygrobot: A self-locomotive ratcheted actuator powered by environmental humidity

Shin, Beomjune; Ha, Jun Seok; Lee, Minhee; Park, Keunhwan; Park, Gee Ho; Choi, Tae Hyun; Cho, Kyu-Jin; Kim, Ho Young

doi:10.1126/scirobotics.aar2629

Cited by 328 publications

(163 citation statements)

References 74 publications

(41 reference statements)

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“…However, these robots are made of rigid or partially rigid parts, resulting in poor robustness and low adaptability to shape changes and/or external perturbations. On the other hand, soft robots actuated by humidity (19)(20)(21), light (22)(23)(24), heat (25), and magnetic force (26)(27)(28) have been demonstrated but have slow responses, whereas others require bulky setups to generate the external power sources such as magnetic fields. Robots using thin film-based actuators based on lead zirconate titanate (PZT) have been successfully developed (17,18,(29)(30)(31), but PZT is a brittle material containing poisonous lead.…”

Section: Introductionmentioning

confidence: 99%

Insect-scale fast moving and ultrarobust soft robot

et al. 2019

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Mobility and robustness are two important features for practical applications of robots. Soft robots made of polymeric materials have the potential to achieve both attributes simultaneously. Inspired by nature, this research presents soft robots based on a curved unimorph piezoelectric structure whose relative speed of 20 body lengths per second is the fastest measured among published artificial insect-scale robots. The soft robot uses several principles of animal locomotion, can carry loads, climb slopes, and has the sturdiness of cockroaches. After withstanding the weight of an adult footstep, which is about 1 million times heavier than that of the robot, the system survived and continued to move afterward. The relatively fast locomotion and robustness are attributed to the curved unimorph piezoelectric structure with large amplitude vibration, which advances beyond other methods. The design principle, driving mechanism, and operating characteristics can be further optimized and extended for improved performances, as well as used for other flexible devices.

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Section: Introductionmentioning

confidence: 99%

Insect-scale fast moving and ultrarobust soft robot

et al. 2019

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“…Inspired by plants with shape‐changing structures caused by anisotropic swelling of fibers, bending of bilayers using anisotropic swelling has been demonstrated with hydrogels of different stiffness . The bending deformation of a bilayer composed of two metals with different coefficients of thermal expansion has most frequently been used to measure temperature, and bilayers consisting of one passive layer and one layer that responds to a stimulus have been used for actuators and robots . Bilayers may also form 3D structures when materials with “mismatching” strain or internal stress are bonded to one another.…”

mentioning

confidence: 99%

Fabricating 3D Structures by Combining 2D Printing and Relaxation of Strain

Cafferty

Campbell

Rothemund

et al. 2018

Adv Materials Technologies

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materials to achieve extreme overhangs, and are limited by trade-offs between the speed of printing and the minimum feature sizes and surface roughness. [8,9] In contrast, "2D printing" techniques (such as digital printing and screen printing) are rapid, relatively inexpensive, and routinely achieve sub-millimeter feature sizes.Nature has also evolved the ability to form complex 3D structures (e.g., leaves, flowers, and tendrils) from initially quasiplanar structures. [10][11][12][13][14][15] These 2D to 3D transformations have inspired the design of synthetic structures that display complex changes in shape when subjected to appropriate stimuli (surface or interfacial stress, edge stress, misfit strain, residual stress, differential growth, swelling, and mechanical instabilities). [16,17] These processes also suggest possible routes to micro-and nanoelectromechanical systems (MEMS and NEMS), [18,19] and to systems for drug delivery, [20] actuation, [19,21] microrobotics, [22,23] and new materials. [23,24] In this paper, we describe a technique to fabricate 3D structures from planar elastomeric bilayers with mismatched strain that is compatible with digital printing. We determine that a relatively simple set of primitive structures printed on a prestretched 2D sheet can result in a variety of complex 3D objects by producing both positive and negative curvature of whole parts, as well as "pop-up" structures on 2D or 3D sheets. This paper describes the fabrication of elastomeric three-dimensional (3D) structures starting from two-dimensional (2D) sheets using a combination of direct-ink printing and relaxation of strain. These structures are fabricated in a two-step process: first, elastomeric inks are deposited as 2D structures on a stretched elastomeric sheet, and second, after curing of the elastomeric inks, relaxation of strain in the 2D sheet causes it to deform into a 3D shape. To predict bending of elastomeric objects fabricated with this technique, a simple mechanical model is developed. The strategy of using initially 2D materials to fabricate 3D structures offers four new features that complement digital fabrication techniques. (i) It provides a simple route to create shapes with complex curves, suspended features, and internal cavities. (ii) It is a faster method of fabricating some types of shapes than "conventional" 3D printing, because the features are printed in 2D. (iii) It forms surfaces that can be both smoother, and structured in a way that is not compatible with layer-by-layer processing. (iv) It forms structures that can be deformed reversibly after fabrication by reapplying strain. This paper demonstrates these features by fabrication of helices, structures inspired by cubes and tables, "pop-up" structures, and soft grippers. 3D PrintingThe term "3D printing" encompasses additive manufacturing techniques that use one or more translational elements (stage and/or printing heads) that are controlled by a computer to move an ink deposition nozzle, or laser-writing optics, to fabricate a digitally ...

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“…Material is crucial for the design of microrobots, which regulates their mechanical properties and further determines their functions. Smart materials, which can sense and react to external stimuli, such as temperature, pH, light, humidity, magnetism, and electric fields, are indispensable for fabricating untethered soft microrobots. However, almost all stimuli–response materials reported exclusively exhibit a monotonic dependence of swelling deformation with some specific stimulus.…”

Section: Introductionmentioning

confidence: 99%

Encoding Smart Microjoints for Microcrawlers with Enhanced Locomotion

Chen

Huang

et al. 2020

Advanced Intelligent Systems

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Usually, it is indispensable for traditional functional robots to use flexible joints that integrate sophisticated machinery and control systems to achieve precise operability and efficient mobility. At the microscale, however, the conventional design of functional joints is generally not suitable due to the limitation of the manufacturing process on such a tiny size. Herein, a strategy for the design of smart microjoints (SMJs) that undergo controllable active deformation by triggering a size‐dependent layer‐by‐layer sequential swelling effect on SMJs in response to external stimuli is developed. The optimal encoding of SMJs that enables microcrawlers to achieve superior crawling speed (0.15 body length s−1) and efficiency (1.1 body length per step), as well as controllable locomotion, is demonstrated, e.g., migration along/against the stimuli source or along a preplanned path. A path toward constructing soft actuators/robots at the microscale with high adaptability and controllability for broad engineering applications is offered.

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Hygrobot: A self-locomotive ratcheted actuator powered by environmental humidity

Cited by 328 publications

References 74 publications

Insect-scale fast moving and ultrarobust soft robot

Insect-scale fast moving and ultrarobust soft robot

Fabricating 3D Structures by Combining 2D Printing and Relaxation of Strain

Encoding Smart Microjoints for Microcrawlers with Enhanced Locomotion

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