**From left to right: Ahmad, Dan, Nivedina, Luke, Gautam, Eric, Yoshi, Oscar**

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# 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 ·

## · 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.

**From left to right: Ahmad, Dan, Nivedina, Luke, Gautam, Eric, Yoshi, Oscar ****From left to right: Ahmad, Dan, Luke, Gautam, Katherine, Yoshi, Adri, Nivedina (Photo Credit: Hyeongjoo Row)**
### Yu-Jen (Yoshi) Chiu

### Daniel Evans

### Jiechao (Oscar) Feng

### David King

### Luke Langford

### Nivedina Sarma

### Eric Weiner

## · Papers ·

## · Teaching ·

## · 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!

- Welcome to new postdoc, David King!!
- Recent works on the mechanics of nucleation, chiral active matter, role of inertia in active phase behavior, and nonequilibrium multicomponent coexistence now available on arXiv! See links in the Papers section!
- The group recently received an award from the Society of Hellman Fellows! Thanks for the support!
- Congratulations to Gautam, Yoshi, Luke, and Nivedina for passing their qualifying exams and Eric and Oscar for passing their preliminary exams!!
- Oscar has been awarded the Jane Lewis Fellowship by the College of Engineering. Way to go, Oscar!
- Gautam’s collaborative work with Xuefei Xu, Tom Russell and a great team is out in Advanced Materials!
- Luke and Dan’s first group papers are now available on arXiv! Luke develops a capillary wave theory for active interfaces while Dan generalizes the theory of symmetry-breaking coexistence to nonequilibrium systems.

Graduate Student (MSE)

B.S. MSE, Penn State

yoshi_chiu@berkeley.edu

Graduate Student (MSE)

B.S. MSE, Michigan

danevans@berkeley.edu

Graduate Student (AS&T)

B.S. Physics, Peking University

jiechao_feng@berkeley.edu

Postdoctoral Scholar

Ph.D., Cambridge University

daking2@lbl.gov

Graduate Student (MSE)

B.S. MSE, UC Berkeley

langford.luke@berkeley.edu

Graduate Student (MSE)

Co-advised w/ Phil Messersmith

B.S. Chemistry, U. Chicago

nivedina@berkeley.edu

Graduate Student (MSE)

B.S. CS and Math, Harvey Mudd

eric_weiner@berkeley.edu

**Theory of Nonequilibrium Multicomponent Coexistence.**Y.J. Chiu*, D. Evans*, A. K. Omar

arXiv:2409.07620**Phase Separation, Capillarity, and Odd Surface Flows in Chiral Active Matter.**L. Langford and A. K. Omar

arXiv:2408.14686 (In Review)**Theory for the Anomalous Phase Behavior of Inertial Active Matter.**

J. Feng and A. K. Omar

arXiv:2407.08676 (In Review)**The Mechanics of Nucleation and Growth and the Surface Tensions of Active Matter.**

L. Langford and A. K. Omar

arXiv:2407.06462 (In Review)**The Flux Hypothesis for Odd Transport Phenomena.**

C. Hargus, A. Deshpande, A. K. Omar, K. K. Mandadapu

arXiv:2405.08798 (In Review)**Theory of Nonequilibrium Coexistence with Coupled Conserved and Nonconserved Order Parameters.**D. Evans and A. K. Omar

arXiv:2309.10341 (In Review)**Theory of Capillary Tension and Interfacial Dynamics of Motility-Induced Phases.**

L. Langford and A. K. Omar

arXiv:2308.08531 (In Review)**Oversaturating Liquid Interfaces with Nanoparticle-Surfactants.**

X. Wu, H. Xue, Z. Fink, B. A. Helms, P. Ashby, A. K. Omar, T. P. Russell

Angew. Chem. Int. Ed.**2024**,*63*, e202403790**Self-Propulsion by Directed Explosive Emulsification.**

X. Wu, H. Xue, G. Bordia, Z. Fink, P. Y. Kim, R. Streubel, J. Han, B. A. Helms, P. Ashby, A. K. Omar, T. P. Russell

Adv. Mater.**2024**, 2310425**Phase Coexistence Implications of Violating Newton’s Third Law.**

Y.-J. Chiu and A. K. Omar

J. Chem. Phys.**2023**,*158*, 164903**Mechanical 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*, e2219900120**Remembering the Work of Phillip L. Geissler: A Coda to His Scientific Trajectory.**

Annu. Rev. Phys. Chem.**2023***, 74,*1**Ballistic 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**, 2213844**Tuning Nonequilibrium Phase Transitions with Inertia.**

A. K. Omar, K. Klymko, T. GrandPre, P. L. Geissler, J. F. Brady

J. Chem. Phys.**2023**,*158*, 074904**Topological Forces in a Model System for Reptation Dynamics.**

A. K. Omar, Y. Lu, L. An, Z.-G. Wang

arXiv:2207.05351**Boundary Design Regulates the Diffusion of Active Matter in Heterogeneous Environments.**

K. J. Modica, A. K. Omar, S. C. Takatori

Soft Matter**2023**,*19*, 1890**The 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*, e2208593119**Dynamic Concentration Scales of Active Colloids.**

S. A. Mallory, A. K. Omar, J. F. Brady

Phys. Rev. E**2021**,*104*, 044612**Phase 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*, 012604**Swimming to Stability: Structural and Dynamical Control***via*Active Doping.

A. K. Omar, Y. Wu, Z.-G. Wang, J. F. Brady

ACS Nano**2019**,*13*, 560**Mechanisms 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,*14185**Shear-Induced Heterogeneity in Associating Polymer Gels: Role of Network Structure and Dilatancy.**

A. K. Omar and Z.-G. Wang

Phys. Rev. Lett.**2017**,*119*, 117801**Analysis 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*, 3796**Aggregation 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*, 330**Complexation 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

**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.