Self-Retracting Motion of Graphite Microflakes

TL;DR

This paper reports the discovery of a self-retracting motion in graphite microflakes, explains the critical size threshold for this phenomenon, and proposes a model involving shear strengths and van der Waals forces, opening avenues for nano-electromechanical systems.

Contribution

The study introduces the novel observation of self-retracting motion in graphite microflakes and provides a theoretical model explaining the phenomenon based on interfacial forces.

Findings

Self-retracting motion occurs in graphite flakes smaller than approximately 35 micrometers.

Larger flakes do not exhibit self-retraction, explaining its absence in natural graphite samples.

The proposed model accounts for static/dynamic shear strengths and van der Waals interactions.

Abstract

We report the observation of a novel phenomenon, the self-retracting motion of graphite, in which tiny flakes of graphite, after being displaced to various suspended positions from islands of highly orientated pyrolytic graphite, retract back onto the islands under no external influences. Our repeated probing and observing such flakes of various sizes indicate the existence of a critical size of flakes, approximately 35 micrometer, above which the self-retracting motion does not occur under the operation. This helps to explain the fact that the self-retracting motion of graphite has not been reported, because samples of natural graphite are typical larger than this critical size. In fact, reports of this phenomenon have not been found in the literature for single crystals of any kinds. A model that includes the static and dynamic shear strengths, the van der Waals interaction force, and the edge dangling bond interaction effect, was used to explain the observed phenomenon. These findings may conduce to create nano-electromechanical systems with a wide range of mechanical operating frequency from mega to giga hertzs.