Engineering Self-Organization in Active Colloidal Mixtures Using Particle Shape
Abstract
We propose a program of research and education focused on self-organization in heterogeneous mixtures of active colloids. As a model system, we will use metallo-dielectric particles that selfpropel in the presence of AC electric fields. Through experiments and multiscale modeling, we will investigate how the microscopic properties of a particle, e.g., shape and surface chemistry, can be engineered to induce hierarchical self-organization of two-, few-, and many-body structures via hydrodynamic and other interactions. In the process, we will develop coarse-grained theoretical frameworks and codes that simplify the design of heterogeneous systems, allow for in silico prediction of phase behavior, and expose universal mechanisms implicated in our findings. As part of this project, we will proactively recruit and provide mentorship for multiple Hawaiian/Pacific Islander (NHPI) undergraduate and graduate students. These students will take creative roles in the direction of the project and have the opportunity to present at leading scientific conferences. Heterogeneity Ð diversity in the number of distinct interacting components -- is a hallmark of cellular biology. As such, it may hold the key to achieving biomimetic systems of synthetic active colloids that self-organize into hierarchically structured materials with life-like functionalities. However, owing to the Òcurse of dimensionality,Ó studies of heterogeneity in synthetic active matter have largely been limited to binary mixtures. This situation calls for the development of new theoretical and computational frameworks that can guide selection of governing parameters for experiments. In recent work, we demonstrated that metallo-dielectric Janus particles with discoidal shape will form bound pairs with low motility. The presence of a bound pair induces additional pair binding events, ultimately leading to separation of an arrested motility phase. Our modeling and analysis revealed that the inter-particle interactions were dominated by hydrodynamics. Moreover, pair formation was driven by an effective aligning interaction that emerges from a coupling between particle-generated flows and particle shape. Our analysis immediately raises the question: what happens in systems of particles with dissimilar shape? Our studies are designed to address this question. We hypothesize that a hierarchical selforganization process can be initiated by engineered anisotropic interactions between particles, using shape, composition, and other microscopic properties as parameters. We anticipate that this hierarchical self-organization -- from pairing at small scales, to clustering and coarsening at larger scales Ð will be an effective route to unlocking new collective behaviors. Our modeling will link three different levels of description: a high-resolution model of induced charge electrophoresis (ICEP); the hydrodynamics-only squirmer model; and a coarse-grained Òpoint-particleÓ description given in terms of prescribed governing equations. This multiscale approach is designed to effectively handle the high-dimensional parameter space of a heterogeneous mixture. Our program will pave the way towards in silico design of heterogeneous active mixtures that can self-organize into functional materials. Moreover, the mapping we will develop between the ICEP system and the generic, widely-used squirmer model will lead to insights that broadly concern many active matter systems, including biological swimmers. Moreover, by proactive recruiting and mentorship, we will tap into and foster latent scientific talent in the Hawaiian/Pacific Islander (NHPI) community.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 24, 2023
- Source ID
- W911NF2310190
Entities
People
- William Uspal
Organizations
- Army Contracting Command
- Office of the Secretary of Defense
- University of Hawaiʻi System