Moisture-sensitive mechanical metamaterials with unusual and re-programmable hygroscopic deformation modes

Yisong, Bai; Liu, Chuanbao; Li, Yang; Li, Jinxu; Qiao, Lijie; Zhou, Ji; Bai, Yang

doi:10.1039/d2mh00670g

Cited by 6 publications

(2 citation statements)

References 56 publications

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“…This counter-intuitive behavior has found applications in various fields, including the development of temperature-stable components for aerospace and electronics applications [22][23][24][25][26]. Similarly, metamaterials have been designed to obtain negative swelling behavior [27][28][29][30][31][32] and negative hygroscopic expansion [33][34][35][36][37], which have applications in the development of humidity-sensitive devices and materials.…”

Section: Introductionmentioning

confidence: 99%

Design of auxetic cellular structures for in-plane response through out-of-plane actuation of stimuli-responsive bridge films

Chandramouli,

Rapaka,

Annabattula

2024

Smart Mater. Struct.

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In this work, we propose novel designs of cellular structures exhibiting unconventional in-plane actuation responses to external stimuli. We strategically introduce stimuli-responsive bilayer bridge films within conventional honeycombs to achieve the desired actuation. The films are incorporated such that, in response to an external field (thermal, electric, chemical, etc.), the bridge film bends out-of-plane, activating the honeycomb in the plane. The conventional out-of-plane deformation of the bridge film can lead to interesting and unconventional actuation in the plane. An analytical model of this coupled unit cell behaviour is developed using curved beam theory, and the model is validated against finite element simulations. Several applications of such designs are presented. Unit cell architectures exhibiting both positive and negative macroscopic actuation are proposed, and the criterion for achieving such actuation is derived analytically. Furthermore, we demonstrate that by altering the topology, unidirectional and bidirectional negative actuation can be achieved. We also propose designs that result in the negative actuation of the structure with both monotonically increasing and monotonically decreasing stimuli. Finally, by combining two macroscopic structures with positive and negative actuation, we design actuators/sensors that bend in the plane in response to a stimulus.

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Section: Introductionmentioning

confidence: 99%

Design of auxetic cellular structures for in-plane response through out-of-plane actuation of stimuli-responsive bridge films

Chandramouli,

Rapaka,

Annabattula

2024

Smart Mater. Struct.

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“…Stimulus-responsive hydrogels represent an interesting candidate for engineering the active components in metamaterial architectures due to their high programmability with multiple stimulus responses. The active hydrogels act as muscles triggering the deformation of the passive frame by pushing, pulling, or bending. − Simple swelling of hydrogel metamaterials can influence the stress–strain behavior due to global swelling or shrinkage of the entire architecture . However, swelling of hydrogel-based metamaterials is almost inevitably accompanied by a change in size, which does not allow their application when the total dimensions have to be kept constant.…”

Section: Introductionmentioning

confidence: 99%

Hard- and Soft-Coded Strain Stiffening in Metamaterials via Out-of-Plane Buckling Using Highly Entangled Active Hydrogel Elements

Skarsetz,

Mathes,

Schmidt

et al. 2024

ACS Appl. Mater. Interfaces

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Metamaterials show elaborate mechanical behavior such as strain stiffening, which stems from their unit cell design. However, the stiffening response is typically programmed in the design step and cannot be adapted postmanufacturing. Here, we show hydrogel metamaterials with highly programmable strainstiffening responses by exploiting the out-of-plane buckling of integrated pH-switchable hydrogel actuators. The stiffening upon reaching a certain extension stems from the initially buckled active hydrogel beams. At low strain, the beams do not contribute to the mechanical response under tension until they straighten with a resulting step-function increase in stiffness. In the hydrogel actuator design, the acrylic acid concentration hard-codes the configuration of the metamaterial and range of possible stiffening onsets, while the pH soft-codes the exact stiffening onset point after fabrication. The utilization of out-of-plane buckling to realize subsequent stiffening without the need to deform the passive structure extends the application of hydrogel actuators in mechanical metamaterials. Our concept of out-of-plane buckled active elements that stiffen only under tension enables strain-stiffening metamaterials with high programmability before and after fabrication.

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Programmable Liquid Metal

Yuan

2024

Handbook of Liquid Metals

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Moisture-sensitive mechanical metamaterials with unusual and re-programmable hygroscopic deformation modes

Abstract: Mechanical metamaterials are of great interest due to their counterintuitive deformation under various fields. However, the research on metamaterials responding to moisture is still rare and the controllable hygroscopic deformation...

Cited by 6 publications

References 56 publications

Design of auxetic cellular structures for in-plane response through out-of-plane actuation of stimuli-responsive bridge films

Design of auxetic cellular structures for in-plane response through out-of-plane actuation of stimuli-responsive bridge films

Hard- and Soft-Coded Strain Stiffening in Metamaterials via Out-of-Plane Buckling Using Highly Entangled Active Hydrogel Elements

Programmable Liquid Metal

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