论文标题

活性泡沫:在环状通货膨胀下2D空气泡沫的自适应力学

Active Foam: The Adaptive Mechanics of 2D Air-Liquid Foam under Cyclic Inflation

论文作者

Kroo, Laurel A., Bull, Matthew Storm, Prakash, Manu

论文摘要

泡沫是无序软质的典型例子,在该局部力量平衡导致许多亚稳态构型的竞争。在这里,我们提出了一个“主动泡沫”的实验和理论框架,其中单个体素会定期膨胀和放气。我们探讨了这种无序材料相对于增加活性的结构适应。周期性注入局部活动会导致整个泡沫中少量的不可逆和可逆T1转变。无论T1过渡的存在如何,单个顶点都会向外移位,然后返回其近似的原始径向位置。这种径向位移遵循逆法。令人惊讶的是,每个返回轨迹都不会追溯其出站路径,而是用CW或CCW方向包围有限区域 - 我们将其定义为本地漩涡。这些漩涡形成了跨越材料整个比例的连贯图案。使用降低的阶动力模型,我们证明漩涡是局部微结构中空间疾病的直接结果。建立第一原理模型,我们证明了障碍和应变率控制相邻顶点中漩涡之间的合作与竞争之间的交叉。在较长的时间尺度上,活动体素周围的区域在结构上从高能亚稳态调整到较低的能量状态,这表明局部退火过程。最后,我们开发了一种统计玩具模型,该统计玩具模型根据一组简单的规则来演变边缘长度,以探讨该类别的材料如何随着时间的推移而适应初始结构的函数。在泡沫夫妇结构障碍和自适应动力学中增加活性,以鼓励开发新的非生物,细胞化活性物质。

Foam is a canonical example of disordered soft matter where local force balance leads to the competition of many metastable configurations. Here we present an experimental and theoretical framework for "active foam" where an individual voxel inflates and deflates periodically. We explore structural adaptations of this disordered material with respect to added activity. Periodic injection of local activity leads to a small number of irreversible and reversible T1 transitions throughout the foam. Regardless of the presence of T1 transitions, individual vertices will displace outwards and subsequently return back to their approximate original radial position; this radial displacement follows an inverse law. Surprisingly, each return trajectory does not retrace its outbound path but rather encloses a finite area, with either a CW or CCW direction - which we define as a local swirl. These swirls form coherent patterns spanning the entire scale of the material. Using a reduced order dynamical model, we demonstrate that swirl arises as a direct consequence of spatial disorder in the local micro-structure. Building a first principles model, we demonstrate that disorder and strain rate control a crossover between cooperation and competition between swirls in adjacent vertices. Over longer timescales, the region around the active voxel structurally adapts from a higher-energy metastable state to a lower energy state, indicative of a localized annealing process. Finally, we develop a statistical toy-model that evolves edge lengths based on a set of simple rules to explore how this class of materials adapts over time as a function of initial structure. Adding activity to foam couples structural disorder and adaptive dynamics to encourage the development of a new class of abiotic, cellularized active matter.

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