Omar Group @ UC Berkeley
Computational and Theoretical Soft Matter
· Research ·
Our research aims to advance our theoretical understanding of both natural and synthetic soft condensed matter systems. We leverage the tools of statistical mechanics, continuum mechanics and computer simulation to bridge microscopic details with the emergent properties and phenomena displayed by these systems. Our current interests are diverse – ranging from the nonequilibrium phase behavior and dynamics of active colloids and driven polymers to understanding the self-assembly pathways of complex phases. The unifying theme in these seemingly disparate areas is the significance of both conservative and nonconservative (e.g., hydrodynamic, active) forces in shaping the underlying dynamic landscape and material properties. We endeavor to investigate this interplay of thermodynamic and dissipative forces by utilizing and devising simulation and analytical techniques at the coarse-grained length and time scales of interest. Moreover, we aim to study systems that have clear connections to experiments and venture to make meaningful and experimentally verifiable predictions.
Interfacial Phenomena
Active Matter and Nonequilibrium Systems
Self-assembly
· Recent News ·
- Congratulations to Hyunshik Choi for receiving the Jane Lewis Fellowship from the College of Engineering!
- Congratulations to Hyunshik Choi for passing the MSE preliminary exam!
- Our first two PhD students — Nivedina Sarma and Gautam Bordia — have graduated!
· People ·
We are a diverse group of scientists that value, respect and welcome people regardless of race, ethnicity, religion, culture, gender identity, sexuality, age and disability.
Yu-Jen (Yoshi) Chiu
Graduate Student (MSE)
B.S. MSE, Penn State
yoshi_chiu@berkeley.edu
Hyunshik Choi
Graduate Student (MSE)
B.S. MSE, Seoul National
hyunshik_choi@berkeley.edu
Daniel Evans
Graduate Student (MSE)
B.S. MSE, Michigan
danevans@berkeley.edu
David King
Postdoctoral Scholar
Ph.D., Cambridge University
daking2@lbl.gov
Luke Langford
Graduate Student (MSE)
B.S. MSE, UC Berkeley
langford.luke@berkeley.edu
Eric Weiner
Graduate Student (MSE)
B.S. CS and Math, Harvey Mudd
eric_weiner@berkeley.edu
Yilong Zhou
Postdoctoral Scholar
Ph.D., Duke University
yzhou5@lbl.gov
· Alumni ·
Graduate and postdoctoral alumni
Gautam Bordia
MSE Ph.D. Fall 2025
Next Stop: Research Associate
at LBNL
Jiechao (Oscar) Feng
AS&T M.S. Spring 2025
Next Stop: PhD at UC Berkeley
Nivedina Sarma
MSE Ph.D. Summer 2025
Next Stop: Technical Advisor at
Desmarais LLP
· Papers ·
Emergent nonreciprocity in open thermodynamically-consistent chemical reaction networks.
D. Evans, Y. Shen, A. K. Omar
arXiv:2604.18528 (In Review)Hexatic Order Coupled with Thermal Noise Produces Bubbles in Two-Dimensional Active Matter.
L. Langford and A. K. Omar
arXiv:2603.17320 (In Revision)Active Particles Destabilize Passive Membranes.
D. A. King, T. P. Russell, A. K. Omar
arXiv:2601.16430 (In Revision)Tunable Nanostructures from Inverse Surfactants.
N. A. Sarma, A. Grigoropoulos, M. Arslan, E. E. Salzman, P. Christakopoulos, H. Zhang, K. G. DeFrates, J. Engström, P. V. Bonnesen, S. V. Pingali, T. Xu, P. B. Messersmith, A. K. Omar
arXiv:2511.12407 (In Revision)Multicomponent Linear Transport in the Absence of Local Equilibrium.
Y.J. Chiu*, E. M. Weiner*, A. K. Omar
arXiv:2505.23906 (In Revision)Dynamic Permeability in Metastable Droplet Interfacial Bilayers.
N. A. Sarma*, D. A. King*, X. Wu, B. A. Helms, P. D. Ashby, T. P. Russell, A. K. Omar
Soft Matter 2026Theory of Nonequilibrium Crystallization and the Phase Diagram of Active Brownian Spheres.
D. Evans and A. K. Omar
Soft Matter 2026, 22, 1962Ion transport through reconfigurable nanoparticle-surfactant stabilized droplet interface bilayers.
X. Wu, H. Xue, Z. Fink, Z. Xia, N. Sarma, X. Gan, J. Katsaras, P. Ercius, B. Rad, B. A. Helms, P. Ashby, A. K. Omar, C. Collier, T. P. Russell
Proc. Natl. Acad. Sci. U. S. A. 2026, 8, e2522349123Theory of Nonequilibrium Coexistence with Coupled Conserved and Nonconserved Order Parameters.
D. Evans and A. K. Omar
Phys. Rev. Research 2025, 7, 043229Theory of Nonequilibrium Multicomponent Coexistence.
Y.J. Chiu*, D. Evans*, A. K. Omar
Phys. Rev. E 2025, 112, 055420Critical Motility-Induced Phase Separation in Three Dimensions is Consistent with Ising Universality.
J. Feng, D. Evans, A. K. Omar
Phys. Rev. E 2025, 112, 055413Self-assembly of anisotropic particles on curved surfaces.
G. Bordia, T. P. Russell, A. K. Omar
ACS Nano 2025, 19, 38803The Mechanics of Nucleation and Growth and the Surface Tensions of Active Matter.
L. Langford and A. K. Omar
J. Chem. Phys. 2025, 163, 064901Shape-Evolving Structured Liquids.
P. Y. Kim, S. Zhu, J. Forth, G. Xie, D. A. King, B. A. Helms, P. D. Ashby, A. K. Omar, T. P. Russell
Adv. Mater. 2025, 2500804Theory for the Anomalous Phase Behavior of Inertial Active Brownian Particles.
J. Feng and A. K. Omar
Phys. Rev. E 2025, 111, L043402Flux Hypothesis for Odd Transport Phenomena.
C. Hargus, A. Deshpande, A. K. Omar, K. K. Mandadapu
Phys. Rev. Lett. 2025, 134, 097105Phase Separation, Capillarity, and Odd-Surface Flows in Chiral Active Matter.
L. Langford and A. K. Omar
Phys. Rev. Lett. 2025, 134, 068301Theory of Capillary Tension and Interfacial Dynamics of Motility-Induced Phases.
L. Langford and A. K. Omar
Phys. Rev. E 2024, 110, 054604
[Editors’ Suggestion]Oversaturating Liquid Interfaces with Nanoparticle-Surfactants.
X. Wu, H. Xue, Z. Fink, B. A. Helms, P. D. Ashby, A. K. Omar, T. P. Russell
Angew. Chem. Int. Ed. 2024, 63, e202403790Self-Propulsion by Directed Explosive Emulsification.
X. Wu, H. Xue, G. Bordia, Z. Fink, P. Y. Kim, R. Streubel, J. Han, B. A. Helms, P. D. Ashby, A. K. Omar, T. P. Russell
Adv. Mater. 2024, 2310425Phase Coexistence Implications of Violating Newton’s Third Law.
Y.-J. Chiu and A. K. Omar
J. Chem. Phys. 2023, 158, 164903Mechanical Theory of Nonequilibrium Coexistence and Motility-Induced Phase Separation.
A. K. Omar*, H. Row*, S. A. Mallory*, J. F. Brady
Proc. Natl. Acad. Sci. U. S. A. 2023, 18, e2219900120Remembering the Work of Phillip L. Geissler: A Coda to His Scientific Trajectory.
Annu. Rev. Phys. Chem. 2023, 74, 1Ballistic Ejection of Microdroplets from Overpacked Interfacial Assemblies.
X. Wu, G. Bordia, R. Streubel, J. Hasnain, C. C. S. Pedroso, B. E. Cohen, B. Rad, P. Ashby, A. K. Omar, P. L. Geissler, D. Wang, H. Xue, J. Wang, T. P. Russell
Adv. Funct. Mater. 2023, 2213844Tuning Nonequilibrium Phase Transitions with Inertia.
A. K. Omar, K. Klymko, T. GrandPre, P. L. Geissler, J. F. Brady
J. Chem. Phys. 2023, 158, 074904Topological Forces in a Model System for Reptation Dynamics.
A. K. Omar, Y. Lu, L. An, Z.-G. Wang
arXiv:2207.05351Boundary Design Regulates the Diffusion of Active Matter in Heterogeneous Environments.
K. J. Modica, A. K. Omar, S. C. Takatori
Soft Matter 2023, 19, 1890The Influence of Molecular Design on Structure-property Relationships of a Supramolecular Prodrug.
K. G. DeFrates*, J. Engström*, N. A. Sarma, A. Umar, J. Shin, J. Cheng, W. Xie, D. Pochan, A. K. Omar, P. Messersmith
Proc. Natl. Acad. Sci. U. S. A. 2022, 44, e2208593119Dynamic Concentration Scales of Active Colloids.
S. A. Mallory, A. K. Omar, J. F. Brady
Phys. Rev. E 2021, 104, 044612Phase Diagram of Active Brownian Spheres: Crystallization and the Metastability of Motility-induced Phase Separation.
A. K. Omar, K. Klymko, T. GrandPre, P. L. Geissler
Phys. Rev. Lett. 2021, 126, 188002
[Cover Article; Editors’ Suggestion; and Featured in Physics Magazine]Microscopic Origins of the Swim Pressure and the Anomalous Surface Tension of Active Matter.
A. K. Omar, Z.-G. Wang, J. F. Brady
Phys. Rev. E 2020, 101, 012604Swimming to Stability: Structural and Dynamical Control via Active Doping.
A. K. Omar, Y. Wu, Z.-G. Wang, J. F. Brady
ACS Nano 2019, 13, 560Mechanisms of Diffusion in Associative Polymer Networks: Evidence for Chain Hopping.
P. B. Rapp*, A. K. Omar*, B. Silverman, Z.-G. Wang, D. A. Tirrell
J. Am. Chem. Soc. 2018, 140, 14185Shear-Induced Heterogeneity in Associating Polymer Gels: Role of Network Structure and Dilatancy.
A. K. Omar and Z.-G. Wang
Phys. Rev. Lett. 2017, 119, 117801Analysis and Control of Chain Mobility in Protein Hydrogels.
P. B. Rapp, A. K. Omar, J. J. Shen, M. E. Buck, Z.-G. Wang, D. A. Tirrell
J. Am. Chem. Soc. 2017, 139, 3796Aggregation Behavior of Rod-Coil-Rod Triblock Copolymers in a Coil-Selective Solvent.
A. K. Omar, B. Hanson, R. T. Haws, Z. Hu, D. A. Vanden Bout, P. J. Rossky, V. Ganesan
J. Phys. Chem. B 2015, 119, 330Complexation between Weakly Basic Dendrimers and Linear Polyelectrolytes: Effects of Grafts, Chain Length, and pOH.
T. Lewis, G. Pandav, A. Omar, V. Ganesan
Soft Matter 2013, 9, 6955
· Teaching ·
MSE 159: Introduction to Soft Matter Soft matter is ubiquitous in synthetic materials and plays a central role in living systems. This course aims to provide students with an introduction to the physics that govern the structure and dynamics of soft mater systems, including polymers, colloids, surfactants, membranes, and active matter. A particular emphasis will be placed on connecting a microscopic physical picture to the emergent phenomena and properties of interest using scaling theory and statistical mechanics. Specific topics will include Brownian motion and colloidal dynamics, the depletion force, polymer chain conformation, rubber elasticity; and surfactant and liquid crystal thermodynamics.
MSE 201B: Thermodynamics, Phase Behavior and Transport Phenomena in Materials This course covers the laws of classical thermodynamics, principles of statistical mechanics, and laws governing the transport of mass and momentum in materials. Applications include the construction of equilibrium and nonequilibrium phase diagrams and the kinetics of phase transformations in both soft and hard materials.
· Contact Us! ·
Our student/postdoc office is located at 248 Hearst Memorial Mining Building (HMMB). Ahmad’s office is located at 225 HMMB. Stop by and visit us!