Anchoring-mediated stick-slip winding of cholesteric liquid crystals

TL;DR

This study investigates how surface anchoring influences stick-slip behaviors during cholesteric liquid crystal unwinding, revealing three distinct regimes and providing insights into static rotational friction dynamics.

Contribution

It demonstrates the existence of constrained, stick-slip, and sliding-slip regimes in cholesteric liquid crystals under mechanical winding, highlighting the role of surface anchoring in these phenomena.

Findings

Identified three regimes: constrained, stick-slip, and sliding-slip.

Measured force responses using Surface Force Balance.

Linked behaviors to elastic and surface torques, informing friction dynamics.

Abstract

The stick-slip phenomenon widely exists in contact mechanics, from the macroscale to the nanoscale. During cholesteric-nematic unwinding by external fields, there is controversy regarding the role of planar surface anchoring, which may induce discontinuous stick-slip behaviors despite the well-known continuous transitions observed in past experiments. Here, we observe three regimes, namely constrained, stick-slip, and sliding-slip, under mechanical winding with different anchoring conditions, and measure the responded forces by the Surface Force Balance. These behaviors result from a balance of cholesteric elastic torque and surface torque, reminiscent of the slip morphology on frictional substrates [T. G. Sano et al., Phys. Rev. Lett. 118, 178001 (2017)], and provide evidence of dynamics in static rotational friction.