Tuesday, August 30, 2016

Symmetry breaking as a general design principle of oscillation-based methods for fixation and manipulation of nano-objects

V.L. Popov, R. Wetter

We present various examples of man-made and biological nanoscale actuators based on oscillations. In most cases it is the interplay of oscillation and friction which produces the driving effect. The basic idea of all such actuators is the same: an asymmetry in the oscillation causes a net directed motion. Introducing asymmetry in different components of the system (internal force, substrate, form of periodic actuation, etc.) leads to different types of drives. This symmetry concept is used to categorize and discuss the basic principles of nanoscale actuation and for formulating general principles of design guidelines that can be used to develop new concepts of nanoscale actuators.
Taking into account the general principle of symmetry breaking, a new concept for a high precision actuator suggested recently by the authors is discussed and its practical realization is outlined. This novel drive type consists of a sphere that is rolling back- and forth while being pushed on a movable substrate. The sphere acts as the drive and the substrate acts as the runner. A varying normal force leads to varying indentation depth and contact area during rolling. Together with the inertia of the runner, this asymmetry enables accurate control of the runner displacement. In theory, the actuator works with less wear because slip is completely omitted.

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