Dataset: Laboratory Sulfate Polystyrene Disaggregation

Polystyrene aggregates were prepared using surfactant-free monodispersed white sulfate latex beads (Interfacial Dynamics Corp.) with a mean diameter of 3 microns. The microspheres were received in an 8% weight by volume solution. To prepare the experiments, 1 mL of the latex solution was diluted in 50 mL of deionized water. We then transferred these to the ~1L disaggregation tank and fully destabilized them by adding calcium chloride at a concentration of 0.5 M. 

Polystyrene experiments were conducted with a particle concentration of ~6700 cells/ml. Cells were aggregated into large aggregates through differential sedimentation by rolling them for 2 days at a rotation rate of 2 rpm prior to creating laminar shear. To create laminar shear and induce disaggregation, the flow motion inside the rotating/oscillating tank was a superposition of a solid body rotation and a harmonic oscillatory flow. We provided an analytical solution to this viscous oscillatory flow in the attached publication. Given proper boundary conditions, this roller tank created calibrated laminar shear that is similar in magnitude to that in the ocean.

With high-speed imaging techniques, we captured the fragmentation of laboratory-made diatom aggregates exposed to the calibrated oscillatory flow. We have also developed a unique image processing method that enabled continuous tracking of particle positions, sizes, and morphologies, as well as the determination of individual aggregate breakup events. The image processing consisted of background removal, particle identification, particle matching, and breakup detection. The analytical solution of fluid flow allowed us to couple the hydrodynamic conditions to the recorded time history. 

Instrument Summary: 

The experimental facility consisted of a transparent acrylic cylindrical tank supported by four identical casters. The tank had an inner diameter of 100 mm and a wall thickness of 5 mm, with a total length of 300 mm. The tank was long enough to have a two-dimensional flow along the central tank cross-section. We controlled the rotation of this tank using an electric servo-motor (Dynamixel MX-28T, Trossen Robotics), programmed with Python. A timing belt drive system that connected the motor to one end of the tank precisely synchronized the rotation with a gear ratio of one. The motor had a resolution of 0.012 rad/s in rotation speed and 0.088º in operating angle. The optical transparency of the tank permitted illumination through the cylinder wall and the imaging of suspended particles through one end of the tank. An LED light panel (StudioPRO S-1200D, Fovitec) shone through a slit aperture (10 mm wide) to illuminate suspended particles along the central tank cross-section. We mounted a high-speed camera (FASTCAM Mini AX200, Photron) with its viewing axis perpendicular to the resulting light sheet. It captured particle motion through a macro lens with a 105 mm focal length (Sigma 105mm f/2.8 EX DG).