Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136, USA.
Soft Matter. 2017 Sep 27;13(37):6332-6339. doi: 10.1039/c7sm00888k.
We investigate emergent behavior in binary mixtures comprised of passive particles and contact-triggered active particles (CAPs), where a propulsion force is applied on CAPs towards passive particles when the two are in contact. We show that such mixtures phase separate into distinct dense and dilute phases with as few as 10% CAPs. Furthermore, the structure of the dense phase can be tuned by varying the fraction of CAPs and the strength of their propulsion force. The dense phase is classified into seven structure types, which includes both 6-fold and 4-fold ordered crystals, and kinetically arrested gels and clusters. Mixtures with fewer than 35% CAPs exhibit traveling density waves such that one end of the dense phase recedes while the other propagates. This phenomenon results from the spontaneous symmetry breaking of particle flux at the dense-dilute interface. We show that contact-triggered activity can be employed to develop materials with a wide range of structures and dynamics.
我们研究了由被动粒子和接触触发的主动粒子 (CAPs) 组成的二元混合物中的突现行为，当两者接触时，会向 CAPs 施加一个推动被动粒子的力。我们发现，这样的混合物可以分成明显的密集相和稀疏相，其中 CAPs 的比例低至 10%。此外，通过改变 CAPs 的比例和推进力的强度，可以调节密集相的结构。密集相分为七种结构类型，包括六重和四重有序晶体，以及动力学停滞的凝胶和团簇。CAPs 比例低于 35%的混合物表现出移动的密度波，使得密集相的一端后退而另一端传播。这种现象源于密集-稀疏界面处粒子流的自发对称破缺。我们表明，接触触发的活性可以用于开发具有广泛结构和动力学的材料。
