Group 1 2014
Sedimentation of Chiral Particles in a Shear Flow
Group members: Johannes Jansson, Brian McMahon, Christian Reitz and Will Savoie
This is the website for the Chiral group. As a project for our Nonlinear Dynamics and Chaos class at Georgia Tech, we are investigating a method for the mechanical separation of chiral particles. As the project progresses, this wiki page will be updated with more material. At the moment you can view our presentation material, whitepaper, data and pictures of our setup at this website.
Abstract
This experiment will attempt to separate particles, which differ in their chirality, via shear flow. We will place 3-D printed twisted ribbon helix particles, with either left and right-handed chirality, in a high viscosity fluid. We will then use a Taylor-Couette apparatus to generate a shear flow which is necessary for the separation of the particles. The shear flow creates a torque on the ribbon particle, the sign of the torque vector depends on the chirality. The results of this experiment should help to further support and verify previous research done by M. Makino and M. Doi. Additionally, our observations should give us a degree of insight into naturally occurring chiral behavior.
Motivation
The behavior of chiral particles is interesting due to their prevalence in biology. Chirality can also be important in the development of drugs, as enantiomers often have differing chemical properties. Shear flow may provide a mechanical separation method whereas most current methods are chemical. Such a method would be of interest to pharmaceutical companies because a mechanical method can prove to be cheaper and easier to perform. Our experiment will grant us a greater understanding of the physics that would be involved in such separation.
Methods
To reach our goals for this experiment, we need a highly viscous fluid in shear flow and, contained in the fluid, particles with of opposing chirality.
The centerpiece of the experiment was a Taylor-Couette device (figure 1). This device creates a reliable shear flow that should be optimal to see the separation effect. The velocity profile of the fluid is a direct result of the inner cylinder's spinning. There velocity will be maximum at the inner wall and drop off as a function of r. The boundary condition on the outer wall requires the velocity to go to zero.
The effect we are demonstrating has only been experimentally examined using rotating parallel plates before, this should be the first time the effect is demonstrated in Taylor-Couette flow. Since the separation effect depends on a high Peclet number, we will be using a highly viscous fluid. Our fluid of choice will be corn syrup. Finally, for chiral particles we went with a ribbon shape.
Throughout this experiment we have chosen to use simple, easily accessible equipment. The Taylor-Couette device was rotated using a cordless drill, the video recording made using a smartphone. All other equipment was either 3-D printed or available at Publix or Home Depot.
