Paper Number
RS13 

Session
Techniques and Methods: Rheometry & Spectroscopy/Microscopy

Title
3-Dimensional manipulation of colloidal particles and liquid droplets using automated flow control

Presentation Date and Time
October 11, 2022 (Tuesday) 4:05

Track / Room
Track 6 / Mayfair

Authors (Click on name to view author profile)

  1. Tu, Michael Q. (University of Illinois at Urbana-Champaign, Chemical and Biomolecular Engineering)
  2. Nguyen, Hung V. (University of Illinois at Urbana-Champaign, Materials and Science Engineering)
  3. Jacobs, Michael I. (University of Illinois at Urbana-Champaign, Beckman Institute for Advanced Science and Technology)
  4. Schroeder, Charles M. (University of Illinois at Urbana-Champaign, Chemical and Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Michael Q. Tu1, Hung V. Nguyen2, Michael I. Jacobs3 and Charles M. Schroeder1
1Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801; 2Materials and Science Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801; 3Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801

Speaker / Presenter 
Nguyen, Hung V.

Keywords
experimental methods; additive manufacturing; colloids; interfacial rheology; microscopy; rheometry techniques; surfactants; suspensions

Text of Abstract
Flow-based manipulation of small particles is an essential tool for studying the dynamics and properties of soft materials. However, prior work on fluidic trapping has extensively relied on using two-dimensional (2D) flows generated in microfluidic devices fabricated by soft lithography. Here, we demonstrate trapping and manipulation of freely suspended particles and droplets using three-dimensional (3D) flow fields including uniaxial extensional flow and biaxial extensional flow. To our knowledge, the 3D Stokes trap is the first reported method for trapping single particles in biaxial extensional flow, which is not commonly studied in microfluidic systems. Flow fields are characterized using particle tracking velocimetry complemented by finite-element simulations for all flow geometries. Single colloidal particles are confined near the stagnation points of uniaxial and biaxial extensional flow using active feedback control for long times (= 10 minutes). In addition, trap stiffness is experimentally determined by analyzing the power spectral density of particle position fluctuations. We further demonstrate the 3D manipulation of particles along user-defined trajectories using automated flow control. In addition, we demonstrate a new capability enabled by the 3D Stokes trap by deforming liquid droplets in both uniaxial and biaxial extensional flows. Overall, this work extends the Stokes trap to three dimensions, thereby enabling quantitative analysis of colloids and soft materials in non-equilibrium flows. This technique opens new avenues for studying deformation in flows with more than one extensional axis and can be used to study the dynamics of soft materials such as lipid vesicles, non-Newtonian droplets, active particles, and linear and ring polymers.