Related Experiment Video
Updated: Mar 3, 2026
09:56
Direct Force Measurements of Subcellular Mechanics in Confinement using Optical Tweezers
Published on: August 31, 2021
5.6K
Optical pressure and numerical simulation of optical forces.
Applied Optics
|April 22, 2017
Summary
Calculating optical forces on particles is improved by using local optical pressure instead of the Maxwell stress tensor. This method reduces numerical noise and mesh requirements, especially for particles near the surrounding medium’s refractive index.
Area of Science:
- Optics
- Computational Physics
- Nanotechnology
Background:
- Optical forces are crucial for manipulating particles.
- Numerical methods are commonly used for calculating these forces.
- The Maxwell stress tensor method can introduce significant numerical noise.
Purpose of the Study:
- To compare the effectiveness of different numerical methods for calculating optical forces.
- To identify a more efficient and accurate method for force calculation.
- To analyze the impact of particle refractive index on calculation accuracy.
Main Methods:
- Numerical integration of the Maxwell stress tensor.
- Calculation of optical force using local optical pressure.
- Comparison with an analytical Mie theory model.
- Analysis of numerical noise and mesh element requirements.
Main Results:
- The Maxwell stress tensor method yields considerable numerical noise for particles with refractive indices close to the surrounding medium.
- Calculating force from local optical pressure significantly reduces numerical noise.
- Fewer mesh elements are required when using the local optical pressure method.
- Results were validated against Mie theory.
Conclusions:
- Local optical pressure is a preferable method for calculating optical forces numerically.
- This method offers improved accuracy and computational efficiency.
- It is particularly advantageous for particles with refractive indices near that of the medium.
Related Concept Videos
01:14Pressure of Fluids
22.3K
There are many examples of pressure in fluids in everyday life, such as in relation to blood (high or low blood pressure) and in relation to weather (high- and low-pressure weather systems). A given force can have a significantly different effect, depending on the area over which the force is exerted. For instance, a force applied to an area of 1 mm2 has a pressure that is 100 times greater than the same force applied to an area of 1 cm2. That's why a sharp needle is able to poke through...
22.3K
01:11Pressure Variation in a Fluid at Rest
907
In a fluid at rest, the pressure at any point beneath the fluid surface depends solely on the depth, not on the container's shape or size. This principle, known as hydrostatic pressure, arises because, in stationary fluids, there is no acceleration, meaning the forces within the fluid balance out. Only vertical forces, caused by the weight of the fluid above, contribute to pressure changes with depth.
When measuring pressure at two different levels within the fluid, the difference in...
When measuring pressure at two different levels within the fluid, the difference in...
907
01:13Basic Equation for Pressure Field
640
The basic equation for a pressure field in fluid mechanics captures the balance of forces within any segment of fluid, providing a foundational understanding of how pressure changes within fluids under various forces. Generally, two main types of forces act on any part of a fluid: surface forces and body forces. Surface forces arise from pressure differences across points within the fluid, which result in net forces that can vary depending on the local pressure gradient. Body forces, on the...
640
01:04Hydrostatic Pressure Force on a Curved Surface
2.6K
Hydrostatic pressure on curved surfaces is a fundamental concept in fluid mechanics with broad applications in the civil engineering field. When fluid is in contact with a curved surface, as in a reservoir, dam, or storage tank, it exerts pressure that varies in magnitude and direction along the curved surface. To assess the total hydrostatic force exerted by the fluid on a curved structure, engineers typically isolate the fluid volume adjacent to the surface and analyze the forces acting on...
2.6K
01:15Concept of Pressure at a Point
857
The concept of pressure at a point in a fluid establishes that pressure within a fluid is uniform in all directions at a specific location. This uniformity occurs because fluid molecules exert force evenly across any point due to their random motion and continuous collisions within the fluid. Pressure at a point is determined by the surrounding fluid molecules and is influenced by factors like depth and density, rather than by shape or orientation.
In a fluid at rest, pressure acts equally in...
In a fluid at rest, pressure acts equally in...
857
01:04Hydrostatic Pressure Force on a Plane Surface
2.2K
When a plane surface is submerged in a fluid, hydrostatic forces develop on the surface due to the fluid's pressure. For horizontal surfaces, the pressure exerted by the fluid is uniform because the depth remains constant. The resultant force is determined by the pressure at the given depth multiplied by the area of the surface, and it acts through the centroid of the surface. For vertical surfaces, the pressure varies with depth, increasing as the distance from the fluid's free surface...
2.2K