Reduced Pressure Drop in Viscoelastic Polydimethylsiloxane Wall Channels

Area of Science:

• Fluid Dynamics
• Materials Science
• Microfluidics

Background:

• Polydimethylsiloxane (PDMS) is a viscoelastic material crucial for microfluidic devices.
• PDMS channel walls can influence fluid dynamics due to their viscoelastic properties.
• Understanding pressure drop in PDMS channels is vital for optimizing microfluidic applications.

Purpose of the Study:

• Investigate pressure drop in PDMS channels bounded by rigid cellulose tubes.
• Analyze the effect of PDMS viscoelasticity on hydrodynamic behavior.
• Determine the relationship between PDMS properties and pressure drop.

Main Methods:

• Fabricated PDMS channels with varying base-to-cross-linker ratios (10:1 to 35:1).
• Measured pressure drop for water and glycerol solutions under laminar flow conditions.
• Quantified PDMS viscoelasticity using loss tangent and correlated with pressure drop.

Main Results:

• Pressure drop decreased as PDMS loss tangent increased, contrary to energy dissipation predictions.
• PDMS channels with lower cross-linker concentrations showed reduced pressure drops.
• A friction factor correlation, f = 47/Re, was approximated for PDMS channels.
• A lubricating effect of PDMS walls was identified as the cause for reduced pressure drop.

Conclusions:

• PDMS viscoelasticity significantly impacts pressure drop in microfluidic channels.
• Increased PDMS loss tangent leads to a lubricating effect, reducing pressure drop.
• Diffusion of oligomers and water at the wall-fluid interface plays a key role in pressure drop reduction.