Date of Award
1-1-2025
Document Type
Thesis
Degree Name
M.S. in Physics
First Advisor
Joel Mobley
Second Advisor
Cecille Labuda
Third Advisor
Likun Zhang
School
University of Mississippi
Relational Format
dissertation/thesis
Abstract
The acoustic radiation force provides the physical mechanism for the non-contact levitation and manipulation of particles in ultrasonic standing wave fields. This thesis presents a study on the measurement, simulation, and validation of acoustic radiation forces acting on spherical particles levitated in air. The motivation for this work is to provide high-precision measurements of acoustic radiation forces in trapping systems, which are of particular interest in biomedical manipulation, materials science, and contactless assembly.
The study employs a three-part methodology: theoretical analysis, experimental observation, and numerical simulation. Theoretically, the acoustic radiation force was derived from Gor’kov’s potential (valid for ka « 1), accounting for both monopole and dipole contributions. The pressure and velocity fields were modeled for a one-dimensional standing wave between an ultrasonic transducer and a rigid reflector operating at 28.66 kHz. The analytical solution revealed a sinusoidal spatial variation in force and pressure nodes suitable for particle trapping.
Experimentally, spherical polystyrene particles with a radius of 2.4 mm and a mass of 26 mg were levitated at the pressure node of the standing wave. The maximum acoustic radiation force was determined by balancing it with the gravitational force, giving a value of 2:55 X 10-4 N. Additionally, pressure measurements were performed, and the resulting data yielded a force estimate of 2:92 X 10-4 N for the first set of data values, 2:78 X 10-4 N for second set, and 2:85 X 10-4 N for the third set of measurements, resulting in a mean force estimate of 2:85 X 10-4 N.
To complement the experiments, a finite element simulation was conducted using COMSOL Multiphysics to solve the Helmholtz equation and compute the acoustic pressure field. From this, the Gor’kov potential was calculated, resulting in a force estimate of 2:51 X 10-4 N.
The close agreement of all three methods, with deviations below 13%, demonstrates the consistency of the approach. This study validates acoustic levitation as a precise tool for measuring micronewton-level forces and establishes a framework with potential applications in force metrology, contactless manipulation, and acoustic particle sorting systems.
Recommended Citation
Rai, Milan, "Measurement of Forces in Standing Wave Ultrasonic Fields" (2025). Electronic Theses and Dissertations. 3366.
https://egrove.olemiss.edu/etd/3366
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