Fluid rheological effects on streaming dielectrophoresis in a post-array microchannel

Area of Science:

• Microfluidics
• Dielectrophoresis
• Non-Newtonian fluid dynamics

Background:

• Insulator-based dielectrophoresis (iDEP) is sensitive to fluid rheology in simple microchannel constrictions.
• The influence of non-Newtonian fluid properties on iDEP in complex geometries remains largely unexplored.
• Understanding these effects is crucial for advanced particle manipulation in microfluidic devices.

Purpose of the Study:

• To experimentally investigate the impact of fluid rheology on streaming dielectrophoresis (sDEP) in a post-array microchannel.
• To compare iDEP behavior in viscoelastic and shear-thinning fluids within a multi-constriction geometry.
• To elucidate the role of microchannel geometry in modulating iDEP phenomena with varying fluid properties.

Main Methods:

• Utilized a post-array microchannel featuring multiple contractions and expansions.
• Employed viscoelastic polyethylene oxide, shear-thinning xanthan gum, and polyacrylamide solutions.
• Observed iDEP focusing and trapping of particles under direct current (DC) electric fields.

Main Results:

• iDEP focusing in polyethylene oxide was comparable to Newtonian fluids, consistent with single-constriction studies.
• Xanthan gum showed insignificant iDEP effects, but unique gel-like structures formed in the post-array under high DC fields.
• Polyacrylamide solutions exhibited significantly weaker iDEP effects compared to single-constriction channels, with observed electroosmotic flow instabilities.

Conclusions:

• The geometry of insulating structures significantly influences the manifestation of iDEP in non-Newtonian fluids.
• Polymer dynamics, particularly in polyacrylamide solutions, appear to be a key factor in the observed weaker iDEP and flow instabilities.
• These findings highlight the complex interplay between fluid rheology, iDEP, and microchannel architecture for particle manipulation.