Integrated Self & Directed Assembly of Multi-Component Colloidal Structures

Johns Hopkins University, Baltimore MD

Investigators

Abstract

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). 0932973 Bevan This proposal is concerned with developing integrated self and directed assembly mechanisms to robustly assemble multi component colloidal systems into more ordered and diverse structures. In prior research, we have demonstrated quantitative connections between interactions, dynamics, and microstructure in unassembled colloidal fluids and as part of independent self-assembly (i.e. colloids assembling themselves) and directed assembly (i.e. external fields assembling colloids). With this foundation, questions related to advancing colloidal assembly include: (1) how can processes be designed to minimize defects in ordered structures (2) how can greater structural diversity (and material properties) be accessed using colloidal components To address these questions, the proposed research aims to systematically extend our current understanding of colloidal assembly by integrating self and directed assembly mechanisms in single component colloidal systems, binary colloidal systems, and in the folding of chains of single and binary colloidal particles. For clarification, binary refers to species with different potentials, which includes different sized colloids, but is intended to refer more generally to any system where species A and B have different AA, BB, and AB interactions. Specific objectives and associated tasks in the proposed research include: (1) (objective1) achieve unprecedented, reliable production of ordered, defect free single component colloidal structures, by (task1) constructively integrating 2D and 3D self and directed assembly processes using kT-scale actuators based on tunable depletion potentials and electric field mediated dipolar interactions, (2) (objective) adapt these approaches to develop new capabilities to assemble binary particle systems into atomic analogues, by (task) identifying tunable AA, BB, AB potentials that allow for implementation of reversible self and directed assembly mechanisms in binary systems, and (3) (objective) extend these findings to colloidal chains that fold into 2D and 3D structures to produce a new class of materials and a new micro scale assembly mechanism, by (task) fabricating single component and binary colloidal chains that fold via condensation due to tunable intra chain attraction and/or compression in inhomogeneous electric fields. The significance of the proposed research is based on its effort to understand how to best control the thermodynamics and kinetics of colloidal assembly processes by exploiting the best aspects of self and directed assembly mechanisms. With a fundamental basis for manipulating colloidal assembly in single component systems, the proposed research also aims to extend the current state of the art for realizing more diverse microstructures and associated material properties. Because colloidal components are amenable to direct real space and real time measurements, the proposed research should also provide broader fundamental insights into the chemical physics of self and directed assembly processes that are not accessible to experiments at smaller length scales. The intellectual merit of the proposed research lies in the fundamental understanding that will be gained of multi component colloidal self and directed assembly through the ability to directly measure, model, and manipulate such systems using coupled microscopy measurements and rigorous models. Such understanding should enable quantitative design, control, and optimization (formal engineering) of colloidal assembly processes and provide new insights beyond what is already known from trial and error discovery. The proposed research can be characterized as transformative based on its anticipated identification of new ways to control defects and to expand the diversity of micro scale structures that can be used as periodic meta materials and manipulated via tunable interactions and sequenced connectivity. The broader impacts of the proposed research plan will result from employing rich visual data from experiments (e.g. images, videos), simulations (e.g. renderings, animations), and analyses (e.g. dynamic, multi-dimensional plots) in various classroom, laboratory, outreach, and dissemination activities.