School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
Nat Mater. 2016 Jan;15(1):54-9. doi: 10.1038/nmat4450. Epub 2015 Oct 26.
Fire ants link their bodies to form aggregations; these can adopt a variety of structures, they can drip and spread, or withstand applied loads. Here, by using oscillatory rheology, we show that fire ant aggregations are viscoelastic. We find that, at the lowest ant densities probed and in the linear regime, the elastic and viscous moduli are essentially identical over the spanned frequency range, which highlights the absence of a dominant mode of structural relaxation. As ant density increases, the elastic modulus rises, which we interpret by alluding to ant crowding and subsequent jamming. When deformed beyond the linear regime, the aggregation flows, exhibiting shear-thinning behaviour with a stress load that is comparable to the maximum load the aggregation can withstand before individual ants are torn apart. Our findings illustrate the rich, collective mechanical behaviour that can arise in aggregations of active, interacting building blocks.
红火蚁通过身体接触形成聚集；这些聚集可以采取多种结构，它们可以滴落和扩散，或者承受施加的负载。在这里，我们通过使用振荡流变学，表明红火蚁聚集是粘弹性的。我们发现，在探测到的最低蚁密度和线性范围内，弹性和粘性模量在跨越的频率范围内基本相同，这突出了没有主导的结构松弛模式。随着蚁密度的增加，弹性模量增加，我们通过暗示蚁群拥挤和随后的堵塞来解释这一点。当变形超出线性范围时，聚集物流动，表现出剪切稀化行为，施加的应力与聚集物在单个蚂蚁被撕裂之前可以承受的最大负载相当。我们的发现说明了在活跃、相互作用的构建块聚集中可能出现的丰富的集体力学行为。
