Liu, B. (2022). Chiral Particle Motion Extracted Using Videogrammetry. Retrieved from https://doi.org/10.14418/wes01.2.361
In 1871, Lord Kelvin proposed an interesting isotropic helicoid model in his paper Hydrokinetic solutions and observations (Thomson, 1871). This model was proposed as an isotropic particle yet has the potential to couple its translational motion to rotational motion, making it one of the simplest chiral particles. However, previous experiments were not able to detect the predicted translation-rotation coupling while a recent theory has shown that the hydrodynamic interactions between the vanes on the particle model allow a tiny but nonzero chiral coupling. In this thesis, we develop a novel videogrammetry method to extract the motion of Lord Kelvin's isotropic helicoid and an anisotropic helicoid model. Additionally, we fabricate two versions of Lord Kelvin's isotropic helicoid by changing the handedness of all the vanes on the particle, which should change the rotation direction resulting from the expected nonzero translation-rotation coupling. Using sedimentation experiments and the videogrammetry method, we successfully observe and quantify an opposite rotation direction of the two types of chiral particles as a result of switching handedness. This opposite rotation direction strongly indicates that the observed rotation is due to the chiral coupling of the isotropic chiral particle. We also measure the translation-rotation coupling of the anisotropic helicoid model. Our measurements indicate that the ratio of the translation-rotation coupling between the isotropic helicoid and the anisotropic helicoid with maximum coupling is about 2.27% ± 0.78%. Our results also confirm that isotropic chiral coupling is much weaker than the possible coupling for anisotropic particles. Nevertheless, a particle with isotropic and chiral coupling is possible.