Molecularly Directed, Geometrically Latched, Impulsive Actuation Powers Sub‐Gram Scale Motility

Jun-feng, Gao; Clement, Arul; Tabrizi, Mohsen; Shankar, M. Ravi

doi:10.1002/admt.202100979

Cited by 7 publications

(4 citation statements)

References 29 publications

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“…Curiously, as the rotation occurs along a degenerate valley, no energy is released, although the configuration of the shell does change in a sub-critical way. This instability does not seem to have previously been discussed theoretically, but it was recently observed experimentally (using a bilyaer structure composed of a passive and singly-curved PET shell and a contractile nematic elastomer layer) and deployed for robotic locomotion [50].…”

Section: Phase Diagram and Instabilitiesmentioning

confidence: 80%

Curvature-driven instabilities in thin active shells

Giudici¹,

Biggins²

2022

Preprint

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Spontaneous material shape changes, such as swelling, growth or thermal expansion, can be used to trigger dramatic elastic instabilities in thin shells. These instabilities originate in geometric incompatibility between the preferred extrinsic and intrinsic curvature of the shell, which may be modified by active deformations through the thickness and in plane respectively. Here, we solve the simplest possible model of such instabilities, which assumes the shells are shallow, thin enough to bend but not stretch, and subject to homogeneous preferred curvatures. We consider separately the cases of zero, positive and negative Gaussian curvature. We identify two types of super-critical symmetry breaking instability, in which the shell's principal curvature spontaneously breaks discrete up-down symmetry and continuous planar isotropy respectively. These are then augmented by inversion instabilities, in which the shell jumps sub-critically between up/down broken symmetry states, and rotation instabilities, in which the curvatures rotate by 90 degrees between states of broken isotropy without release of energy. Each instability has a thickness independent threshold value for the preferred extrinsic curvature proportional to the square-root of Gauss curvature. Finally, we show that the threshold for the isotropy-breaking instability is the same for deep spherical caps, in good agreement with recently published data.

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Section: Phase Diagram and Instabilitiesmentioning

confidence: 80%

Curvature-driven instabilities in thin active shells

Giudici¹,

Biggins²

2022

Preprint

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“…(Scale bars, 3 mm.) ( E ) Comparison of the bending angle versus the size of voltage-driven soft actuators with 3D-to-3D shape morphing capability, for various actuation mechanisms (i.e., LCE-based actuation ( 36 – 38 ), thermal expansion ( 18 , 31 , 39 – 42 ), ionic polymer-metal composites (IPMC)-based actuation ( 43 – 45 ), electrostatic actuation ( 46 – 48 ), piezoelectric actuation ( 49 ), dielectric elastomer-based actuation ( 6 , 50 – 52 ), SMA-based actuation ( 53 – 55 ), and shape-memory-polymer (SMP)-based actuation ( 56 , 57 )), excluding those that can work only in liquid media. The dots marked with large gray circles highlight the voltage-driven actuators that can achieve complex 3D-to-3D shape morphing.…”

Section: Resultsmentioning

confidence: 99%

A soft microrobot with highly deformable 3D actuators for climbing and transitioning complex surfaces

Pang

et al. 2022

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

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The climbing microrobots have attracted growing attention due to their promising applications in exploration and monitoring of complex, unstructured environments. Soft climbing microrobots based on muscle-like actuators could offer excellent flexibility, adaptability, and mechanical robustness. Despite the remarkable progress in this area, the development of soft microrobots capable of climbing on flat/curved surfaces and transitioning between two different surfaces remains elusive, especially in open spaces. In this study, we address these challenges by developing voltage-driven soft small-scale actuators with customized 3D configurations and active stiffness adjusting. Combination of programmed strain distributions in liquid crystal elastomers (LCEs) and buckling-driven 3D assembly, guided by mechanics modeling, allows for voltage-driven, complex 3D-to-3D shape morphing (bending angle > 200°) at millimeter scales (from 1 to 10 mm), which is unachievable previously. These soft actuators enable development of morphable electroadhesive footpads that can conform to different curved surfaces and stiffness-variable smart joints that allow different locomotion gaits in a single microrobot. By integrating such morphable footpads and smart joints with a deformable body, we report a multigait, soft microrobot (length from 6 to 90 mm, and mass from 0.2 to 3 g) capable of climbing on surfaces with diverse shapes (e.g., flat plane, cylinder, wavy surface, wedge-shaped groove, and sphere) and transitioning between two distinct surfaces. We demonstrate that the microrobot could navigate from one surface to another, recording two corresponding ceilings when carrying an integrated microcamera. The developed soft microrobot can also flip over a barrier, survive extreme compression, and climb bamboo and leaf.

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“…Boston Dynamics, Agility Robotics) are becoming increasingly common but their large, heavy power units still limit them. Insect-inspired electrostatic [145] or polymer [146] based actuators offer promise for lighter, lower-power propulsion systems for insect scale robots. And while research into gut-inspired power generation is ongoing, it is tantalising to consider the possibilities of solar-driven robots inspired by photosynthesising aphids [147].…”

Section: Discussionmentioning

confidence: 99%

A virtuous cycle between invertebrate and robotics research: perspective on a decade of Living Machines research

et al. 2023

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Many invertebrates are ideal model systems on which to base robot design principles due to their success in solving seemingly complex tasks across domains while possessing smaller nervous systems than vertebrates. Three areas are particularly relevant for robot designers: Research on flying and crawling invertebrates has inspired new materials and geometries from which robot bodies (their morphologies) can be constructed, enabling a new generation of softer, smaller, and lighter robots. Research on walking insects has informed the design of new systems for controlling robot bodies (their motion control) and adapting their motion to their environment without costly computational methods. And research combining wet and computational neuroscience with robotic validation methods has revealed the structure and function of core circuits in the insect brain responsible for the navigation and swarming capabilities (their mental faculties) displayed by foraging insects. The last decade has seen significant progress in the application of principles extracted from invertebrates, as well as the application of biomimetic robots to model and better understand how animals function. This Perspectives paper on the past 10 years of the Living Machines conference outlines some of the most exciting recent advances in each of these fields before outlining lessons gleaned and the outlook for the next decade of invertebrate robotic research.

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Molecularly Directed, Geometrically Latched, Impulsive Actuation Powers Sub‐Gram Scale Motility

Cited by 7 publications

References 29 publications

Curvature-driven instabilities in thin active shells

Curvature-driven instabilities in thin active shells

A soft microrobot with highly deformable 3D actuators for climbing and transitioning complex surfaces

A virtuous cycle between invertebrate and robotics research: perspective on a decade of Living Machines research

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