Paper Number
PO78 

Session
Poster Session

Title
Dynamics of anisotropic Brownian particles by simultaneous control of position and orientation

Presentation Date and Time
October 23, 2019 (Wednesday) 6:30

Track / Room
Poster Session / Ballroom C on 4th floor

Authors (Click on name to view author profile)

  1. Kumar, Dinesh (University of Illinois at Urbana-Champaign, Chemical and Biomolecular Engineering)
  2. Shenoy, Anish (University of Illinois at Urbana-Champaign, Mechanical Science and Engineering)
  3. Richter, Channing (University of Illinois at Urbana-Champaign, Chemical and Biomolecular Engineering)
  4. Schroeder, Charles M (University of Illinois at Urbana-Champaign, Chemical and Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Dinesh Kumar1, Anish Shenoy2, Channing Richter1, and Charles M Schroeder1
1Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801; 2Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Champaign, IL 61820

Speaker / Presenter 
Kumar, Dinesh

Text of Abstract
In this work, we demonstrate simultaneous control over the 2D center-of-mass position and orientation of anisotropic Brownian particles using only fluid flow. In particular, we use a 4-channel microfluidic device with a model-predictive control scheme to generate a flow pattern that translates and rotates rod-like particles from their initial state to a final desired position and orientation. By quantitative experiments and modeling, we show how the rotational Peclet number (Pe) affects the orientation distribution dynamics of anisotropic particles in a steady extensional flow. Next, we investigate the orientation dynamics of anisotropic particles in time-dependent oscillatory extensional flow over a wide range of Peclet number (Pe) and Deborah number (De). Specifically, we measure the orientation distribution function of rod-like particles as a function of time. In this way, we present the dynamic shapes of Lissajous curves for anisotropic particles as a function of Pe and De using precise microfluidic techniques and fluorescence microscopy. These results are compared with theory by solving the Fokker-Planck equation for orientation distribution function in oscillatory extensional flow. We also describe the non-equilibrium phase diagram of rods, describing the transition from isotropic (disordered) state to the aligned (ordered) state as a function of ow strength and cycle period of oscillatory extensional flow. Overall, the technique of controlling the 2D center-of-mass and orientation of anisotropic particles allows for the direct observation of single rod-like particle dynamics in well-defined time-dependent flows.