Research

From the earth beneath our feet, to the tissue that protects our bodies, to the vast supplies of grain stored in silos for distribution around the world— we are surrounded by disordered, particulate materials. Under pressure, these materials jam, forming solids with an amorphous structure. Like all solids, jammed amorphous materials elastically deform under external loading until a threshold stress is reached, at which point they catastrophically yield and flow. Understanding where and how jammed and disordered systems yield is crucial for designing failure-resistant materials, and has additional profound consequences for phenomena ranging from landscape evolution to cellular unjamming during tumor metastasis.

In our lab, we tackle this problem via two distinct projects:

1. Using the framework of linear control theory to predict how disordered systems respond to external input, and ultimately to design the mechanical response of these systems under stress.

2. Investigating how systems of deformable particles respond to stress. We are currently examining the relationship between networks of forces in these systems, their structure, and their rearrangement dynamics. 

The mechanical, optical, and chemical properties of a wide variety of soft materials are enabled and constrained by their bulk structure. How this structure emerges at small system sizes during self-assembly has been the subject of decades of research, with the aim of designing and controlling material functionality. 

We investigate the emergence of bulk structure in a simple model for complex crystallization. This model uses multi-well isotropic pair potentials to encode multiple preferred length scales into the system, allowing us to understand how anisotropic structural motifs---as opposed to close-packing---emerge as cluster size increases. Our findings demonstrate that tuning particle-particle interactions can enable the engineering of nano- or mesoscale soft matter clusters, in applications as diverse as drug delivery and hierarchical materials design. 

The diffusion of guest particles through porous media can be found in a variety of systems, including metal-organic frameworks used for filtration or gas capture, and designer DNA origami structures with programmable shapes. We model diffusion in simple lattices made from self-assembling cage-like elements in order to understand the relationship between guest particle geometry, lattice geometry and structure, and diffusion dynamics. The ultimate aim of this project is to provide a roadmap for the control of structure and dynamics of a diffusing species through a self-assembled porous material.

Collective behavior is a key component of humanity’s success story. Through interaction and collaboration, groups of humans have built edifices and bridges, discovered vaccines, developed complex languages, and accumulated over generations a collective knowledge stored in the structure of society. 

To investigate fundamental principles leading to the emergence of collective human behavior, we examine collaboration in groups of humans as they play a well-controlled and tunable online game. We examine collaboration through the lens of statistical physics (in particular network theory and information theory), and find that collaboration among humans reliably emerges and can be enhanced or suppressed through the introduction of constraints. Our results contribute to a broader understanding of emergent collective intelligence during active team collaboration, and point toward causal mechanisms for that emergence in a model environment.