Colloidal and biomolecular assemblies out of equilibrium

Colloids and polymers forming crystals, coordinated motion, and phase-separated condensates — Harnessing interactions and activity to shape assembly, motion, and phase behavior.

Colloidal assemblies offer a uniquely observable and tunable platform for discovering new material structures and properties, while biomolecular assemblies play central roles in cellular organization and function. Equilibrium descriptions emphasize free-energy landscapes, leaving unresolved the dynamical processes that determine how assemblies form and reorganize. We investigate how specific and nonspecific interactions, molecular shape, and many-body hydrodynamics influence binding, select assembly pathways, and alter structures and phase behavior. We also study how activity and nonreciprocal interactions produce cooperative motion, pattern formation, and nonequilibrium steady states. By learning, disentangling, and optimizing these interactions and forces, we seek principles for controlling self-assembly, engineering soft and biological materials with new structures and functions, and informing strategies to control protein aggregation in disease.

Selected work

Macromolecular interactions and geometrical confinement determine the 3D diffusion of ribosome-sized particles in live Escherichia coli cells

Diana Valverde-Mendez*, Alp M. Sunol*, Benjamin P. Bratton, Morgan Delarue, Jennifer L. Hofmann, Joseph P. Sheehan, Zemer Gitai, Liam J. Holt, Joshua W. Shaevitz, and Roseanna N. Zia. *Equal contribution.

Proceedings of the National Academy of Sciences · 2025

Direct 3D measurement of homogeneous nucleation of nearly hard-sphere colloids

Zizhao Wang*, Alp M. Sunol*, Alex Young, Debora Walker, Michael P. Brenner, David A. Weitz, and Frans Spaepen. *Equal contribution.

In preparation · 2026

Confined Brownian suspensions: Equilibrium diffusion, thermodynamics, and rheology

Alp M. Sunol and Roseanna N. Zia

Journal of Rheology · 2023

Colloidal physics modeling reveals how per-ribosome productivity increases with growth rate in Escherichia coli

Akshay J. Maheshwari, Alp M. Sunol, Emma Gonzalez, Drew Endy, and Roseanna N. Zia

mBio · 2023

Ribosomal L12 stalks recruit elongation factors to speed protein synthesis in Escherichia coli

Jennifer L. Hofmann, Theodore S. Yang, Alp M. Sunol, and Roseanna N. Zia

Communications Biology · 2025