Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom.
Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA.
Phys Rev Lett. 2018 Oct 26;121(17):178001. doi: 10.1103/PhysRevLett.121.178001.
A zero mode, or floppy mode, is a nontrivial coupling of mechanical components yielding a degree of freedom with no resistance to deformation. Engineered zero modes have the potential to act as microscopic motors or memory devices, but this requires an internal actuation mechanism that can overcome unwanted fluctuations in other modes and the dissipation inherent in real systems. In this Letter, we show theoretically and experimentally that complex zero modes in mechanical networks can be selectively mobilized by nonequilibrium activity. We find that a correlated active bath actuates an infinitesimal zero mode while simultaneously suppressing fluctuations in higher modes compared to thermal fluctuations, which we experimentally mimic by high frequency shaking of a physical network. Furthermore, self-propulsive dynamics spontaneously mobilize finite mechanisms as exemplified by a self-propelled topological soliton. Nonequilibrium activity thus enables autonomous actuation of coordinated mechanisms engineered through network topology.
零模式或软模式是机械部件之间非平凡的耦合，产生了一种对变形没有抵抗力的自由度。工程零模式具有作为微观马达或存储设备的潜力，但这需要一个内部致动机制，该机制可以克服其他模式中的不希望的波动和实际系统中固有的耗散。在这封信中，我们从理论和实验上表明，机械网络中的复杂零模式可以通过非平衡活性来选择性地调动。我们发现，相关的活性浴会驱动一个无穷小的零模式，同时与热波动相比抑制了更高模式的波动，我们通过物理网络的高频振动来实验模拟这种情况。此外，自推进动力学自发地调动有限的机制，例如自推进的拓扑孤子。因此，非平衡活性使得通过网络拓扑设计的协调机制的自主致动成为可能。
