Sublinear drag regime at mesoscopic scales in viscoelastic materials

Area of Science:

• Soft Matter Physics
• Rheology
• Bioengineering

Background:

• Stressed soft materials commonly display viscoelastic behaviors like power-law or exponential decay.
• Power-law dependencies are particularly observed in complex materials such as living cells.
• Understanding microscale mechanisms is crucial for macroscale rheologic behaviors in material design and bioengineering.

Purpose of the Study:

• To numerically reproduce viscoelastic relaxations using an elastic network model.
• To investigate how microscopic interactions influence macroscopic rheologic responses.
• To determine the conditions under which power-law versus exponential decays arise.

Main Methods:

• Utilized an elastic network model of macromolecules in a viscous fluid.
• Simulated particle interactions with spring constants (k) and non-linear drag (γvα).
• Analyzed the effect of mesoscopic parameters (k, γ, α) on viscoelastic responses.

Main Results:

• Successfully reproduced both exponential and power-law viscoelastic relaxations.
• Found that power-law responses emerge specifically under sublinear drag force regimes (0.3 ⪅ α ⪅ 0.45).
• Identified exponential decays as the more common behavior, occurring at different α ranges (0.0 ⪅ α ⪅ 0.2 and 0.55 ⪅ α ⪅ 1.0).

Conclusions:

• Microscopic interactions, particularly the drag parameter α, control rheological responses in intermediate soft materials.
• Sublinear drag forces are the key to observing power-law viscoelasticity in these systems.
• The study provides a mechanistic link between molecular-level interactions and bulk material properties.