Directional Rotation Induced By Spontaneous Symmetry Breaking

Active matter is a self-propelling material which converts chemical energy into mechanical energy.It is of great significance to design nano or micro devices to obtain energy from these substances.In this thesis,we used molecular dynamics simulation to study the behavior of passive flexible ratchet in non-equilibrium active particle bath.We designed two geometric shapes of Brown particles: spherical and rod-shaped.The result indicated that the flexible ratchet was able to rotate directionally in the spherical Brown particle bath.The density and pressure distribution of the active particles near the ratchet are not uniform,resulting in a certain asymmetry in the morphology of the ratchet,which induces the directional rotation of the ratchet.In addition,we studied the effects of the number of ratchet brackets,the size of propelling force and the shape of the particles on the rotation efficiency.The simulation implied that the number of low stents,large propelling force means high rotation speed.The efficiency of the rod-like particle system was significantly lower than that of the spherical particle system.A detailed observation of particle behavior revealed that rod-like particles were easily deposited to the ratchet boundary,weakening the generation of asymmetry.The results of this thesis can provide some theoretical reference for designing new flexible nano devices.