Coarse-grained depletion potentials for anisotropic colloids: Application to lock-and-key systems

Area of Science:

• Colloid and interface science
• Soft matter physics
• Computational chemistry

Background:

• Mixing colloids with depletants (e.g., polymers) induces attractive effective interactions.
• Analyzing these interactions is complex for anisotropic colloidal particles.
• Existing models struggle to accurately capture depletion effects for non-spherical colloids.

Purpose of the Study:

• To present a novel method for inferring approximate effective interaction potentials between anisotropic colloidal particles in the presence of depletants.
• To demonstrate the method's applicability using indented (lock-and-key) colloids as a model system.
• To provide a framework for coarse-graining depletant effects in complex colloidal systems.

Main Methods:

• Numerical integration to "integrate out" the depletant degrees of freedom.
• Matching contributions to the second virial coefficient for accurate potential characterization.
• Developing a coarse-grained depletion potential for anisotropic particles.

Main Results:

• The proposed method accurately characterizes effective interactions between indented colloids.
• Numerical solutions effectively model the depletion potential arising from hard-sphere depletants.
• The simplest implementation yields a piecewise-constant effective potential, with extensions possible.

Conclusions:

• The developed method provides an accurate and efficient way to determine effective interactions for anisotropic colloids with depletants.
• This coarse-graining approach simplifies the analysis of complex colloidal systems.
• The technique is adaptable for various functional forms of effective potentials.