Entangled Granular Media

Gravish, Nick; Franklin, Scott; Hu, David L.; Goldman, Daniel I.

doi:10.1103/physrevlett.108.208001

Cited by 119 publications

(132 citation statements)

References 26 publications

(34 reference statements)

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“…The Journal of Experimental Biology (2014) Shown are mean and 95% confidence intervals of ϕ for live and dead ants (present study), staples (Gravish et al, 2012) and spherocylinders (Wouterse et al, 2007). All values are for body aspect ratios of α=4.…”

Section: Research Articlementioning

confidence: 99%

“…Entanglement is the ability of convex particles to interpenetrate one another and act cohesively. Gravish et al studied the packing of staples, or U-shaped particles (Gravish et al, 2012). Using a plug of entangled staples, they elicited a phase transition from solid to liquid to gas by vibrating the plug, demonstrating that staple barb length is a key parameter for determining activation energy for this transition.…”

Section: Research Articlementioning

confidence: 99%

“…Studies of entangled staples also provide insight into the mechanism underlying the decreased packing fraction of live ants. Gravish et al studied the geometrically induced cohesion of granular U-shaped particles, or staples (Gravish et al, 2012). They consider a dimensionless number Ω staples to describe the barbs, the ratio of barb length l to spine length w (shown in Fig.…”

Section: Research Articlementioning

confidence: 99%

“…To test this we averaged the data in 1 mm 2 bins and found the resulting R Both live and dead ants are provided for comparison. Results from studies of cylinders (Wouterse et al, 2007) and staples (Gravish et al, 2012) are provided to give perspective. Packing fraction ϕ is averaged from four live samples and from two dead samples.…”

Section: Nearest Neighbor Distance and Packing Fractionmentioning

confidence: 99%

“…To gain insight into whether leg geometry influenced the packing fraction of ants, we looked at the studies of Gravish et al (Gravish et al, 2012) on staple-shaped particles of analogous dimensions. We compared the effect of barbs on the packing of staples with the effect of legs on the packing of ants.…”

Section: Comparison With Simulationsmentioning

confidence: 99%

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Fire ants actively control spacing and orientation within self-assemblages

Foster

Mlot

Lin

et al. 2014

Journal of Experimental Biology

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To overcome obstacles and survive harsh environments, fire ants link their bodies together to form self-assemblages such as rafts, bridges and bivouacs. Such structures are examples of self-assembling and self-healing materials, as ants can quickly create and break links with one another in response to changes in their environment. Because ants are opaque, the arrangement of the ants within these threedimensional networks was previously unknown. In this experimental study, we applied micro-scale computed tomography, or micro-CT, to visualize the connectivity, arrangement and orientation of ants within an assemblage. We identified active and geometric mechanisms that ants use to obtain favorable packing properties with respect to wellstudied packing of inert objects such as cylinders. Ants use their legs to push against their neighbors, doubling their spacing relative to random packing of cylinders. These legs also permit active control of their orientation, an ability ants use to arrange themselves perpendicularly rather than in parallel. Lastly, we found an important role of ant polymorphism in promoting self-aggregation: a large distribution of ant sizes permits small ants to fit between the legs of larger ants, a phenomenon that increases the number of average connections per ant. These combined mechanisms lead to low packing fraction and high connectivity, which increase raft buoyancy and strength during flash floods.

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Section: Research Articlementioning

confidence: 99%

Section: Research Articlementioning

confidence: 99%

Section: Research Articlementioning

confidence: 99%

Section: Nearest Neighbor Distance and Packing Fractionmentioning

confidence: 99%

Section: Comparison With Simulationsmentioning

confidence: 99%

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Fire ants actively control spacing and orientation within self-assemblages

Foster

Mlot

Lin

et al. 2014

Journal of Experimental Biology

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Entangled Granular Media

Gravish

Goldman

2016

Fluids, Colloids and Soft Materials: An Introduction to Soft Matter Physics

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We study the geometrically induced cohesion of ensembles of granular ''u particles'' that mechanically entangle through particle interpenetration. We vary the length-to-width ratio l=w of the u particles and form them into freestanding vertical columns. In a laboratory experiment, we monitor the response of the columns to sinusoidal vibration (with peak acceleration À). Column collapse occurs in a characteristic time which follows the relation / expðÀ=ÁÞ. Á resembles an activation energy and is maximal at intermediate l=w. A simulation reveals that optimal strength results from competition between packing and entanglement.

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A Unified View on Nanoscale Packing, Connectivity, and Conductivity of CNT Networks

Gnanasekaran

Grimaldi

With

et al. 2019

Adv Funct Materials

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The design of functional structures from primary building blocks requires a thorough understanding of how size, shape, and particle-particle interactions steer the assembly process. Specifically, for electrically conductive networks build from carbon nanotubes (CNTs) combining macroscopic characterization and simulations shows that the achievable conductivity is mainly governed by CNT aspect ratio, length dispersity and attractive interactions. However, a direct link between the actual 3D network topology that leads to the observed electrical conductivity has not been established yet due to a lack in nanoscale experimental approaches. Here it is shown experimentally for randomly packed (jammed) CNT networks that the CNT aspect ratio determines, as theoretically predicted, the contact number per CNT which in turn scales linearly with the resulting electrical conductivity of the CNT network. Furthermore, nanoscale packing density, contact areas, contact distribution in random and nonrandom configurations, and least resistance pathways are quantified. The results illustrate how complex nanoscale networks can be imaged and quantified in 3D to understand and model their functional properties in a bottom-up fashion.

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Entangled Granular Media

Cited by 119 publications

References 26 publications

Fire ants actively control spacing and orientation within self-assemblages

Fire ants actively control spacing and orientation within self-assemblages

Entangled Granular Media

A Unified View on Nanoscale Packing, Connectivity, and Conductivity of CNT Networks

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