Related Experiment Video
Updated: Jun 8, 2026
06:24
High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
Published on: October 31, 2019
Rotational solid friction of a nematic liquid crystal
Christophe Blanc1, Mathieu Nespoulous, Emmanuel Angot
1Laboratoire des Colloïdes, Verres et Nanomatériaux, UMR5587 CNRS and Université Montpellier II, Place Eugène Bataillon, 34095 Montpellier, France.
Physical Review Letters
|September 28, 2010
Summary
Defects in liquid crystals reveal unexpected solid friction forces during surface reorientation. This friction may stem from director pinning caused by surface disorder on alignment layers.
Area of Science:
- Materials Science
- Soft Matter Physics
- Surface Science
Background:
- Liquid crystals (LCs) exhibit unique director reorientation dynamics influenced by surface alignment layers.
- Understanding surface director behavior is crucial for LC display technologies and other applications.
- SiO(x) alignment layers are commonly used but their surface properties can introduce complex interactions.
Purpose of the Study:
- To investigate the local reorientation dynamics of the nematic surface director on SiO(x) alignment layers.
- To identify the origin of unexpected forces observed during director reorientation.
- To explore the role of surface disorder in influencing director dynamics.
Main Methods:
- Utilizing liquid crystal defects as probes to monitor director reorientation.
- Tracking the motion of these defects with high precision.
- Analyzing the forces acting on the defects based on their observed motion.
Main Results:
- Observed solid friction forces during the reorientation of the nematic surface director.
- These solid friction forces were unexpected in the context of a viscous fluid.
- Identified director pinning by surface quenched disorder as a potential cause for the observed friction.
Conclusions:
- Liquid crystal defect motion provides insights into surface director dynamics.
- Solid friction is a significant factor in nematic surface reorientation on SiO(x) layers.
- Surface quenched disorder plays a critical role in generating director pinning and solid friction.
Related Concept Videos
01:09Rolling Without Slipping
People have observed the rolling motion without slipping ever since the invention of the wheel. For example, one can look at the interaction between a car's tires and the surface of the road. If the driver presses the accelerator to the floor so that the tires spin without the car moving forward, there must be kinetic friction between the wheels and the road's surface. If the driver slowly presses the accelerator, causing the car to move forward, the tires roll without slipping. It is essential...
01:30Dry Friction
Dry friction occurs between two solid surfaces in contact as they attempt to move relative to one another. In daily life, dry friction is encountered in various forms, such as when walking on the ground, sliding an object across a table, or rubbing hands together. Despite its ubiquity, the underlying mechanisms behind dry friction are not readily visible.
To illustrate this concept, imagine a wooden crate resting on a rough, non-uniform horizontal surface. When an external force is applied to...
To illustrate this concept, imagine a wooden crate resting on a rough, non-uniform horizontal surface. When an external force is applied to...
01:34Fluid Mosaic Model
The fluid mosaic model was first proposed as a visual representation of research observations. The model comprises the composition and dynamics of membranes and serves as a foundation for future membrane-related studies. The model depicts the structure of the plasma membrane with a variety of components, which include phospholipids, proteins, and carbohydrates. These integral molecules are loosely bound, defining the cell’s border and providing fluidity for optimal function.LipidsThe most...
01:19Fluid Mosaic Model
Scientists identified the plasma membrane in the 1890s and its principal chemical components (lipids and proteins) by 1915. The model for plasma membrane structure, proposed in 1935 by Hugh Davson and James Danielli, was the first model to be widely accepted in the scientific community. The model was based on the plasma membrane's "railroad track" appearance in early electron micrographs. Davson and Danielli theorized that the plasma membrane's structure resembled a sandwich with the analogy of...
01:07Frictional Force
When a body is in motion, it encounters resistance because the body interacts with its surroundings. This resistance is known as friction, a common yet complex force whose behavior is still not completely understood. Friction opposes relative motion between systems in contact, but also allows us to move. Friction arises in part due to the roughness of surfaces in contact. For one object to move along a surface, it must rise to where the peaks of the surface can skip along the bottom of the...
01:13Contact Angle
When a solid is dipped inside a liquid, the liquid surface becomes curved near the contact. For some solid–liquid interfaces, the liquid is pulled up along the solid, while for others, the liquid surface is convex or depressed near the solid surface. This phenomenon can be explained using the concept of cohesive and adhesive forces.
The adhesive force is the molecular force between molecules of different materials, that is, between the molecules of the solid and the liquid. The cohesive force...
The adhesive force is the molecular force between molecules of different materials, that is, between the molecules of the solid and the liquid. The cohesive force...