Driven Assembly at the Nanoscale
Rationale: Strategies to date for nanoscale assembly have largely revolved around searches for thermodynamic equilibrium to attain desirable end states. Supplementing traditional assembly techniques with the rational use of internal and external fields, and removing the constraints imposed by equilibrium conditions, offers substantial opportunities to expand the phase-space and options available for directed assembly. Little is currently known about beyond-equilibrium assembly at the nanoscale.
Mission: Thrust 3 explores and aims to harness non-equilibrium processes, such as the use of flow and electric fields, for controlled assembly and manipulation of nanoscale objects, including particles and macromolecules. Thrust 3 adopts a truly concerted experimental cycle of prediction, validation and exploration to develop a fundamental understanding of driven assembly, beyond equilibrium, at the nanoscale. Consistent with the diagram of Figure 1, Thrust 3 seeks to develop a general and comprehensive understanding of driven assembly across multiple platforms. These include driven assembly of simple particles in highly structured media, such as nematic liquid crystals, and driven assembly of highly structured, patterned nanoscale entities such as DNA macromolecules in simple, isotropic solvents.
Long-Term Goals: The phenomena that Thrust 3 seeks to discover and exploit rely on the coupling between various elements of a system’s internal structure and the applied field. This coupling varies considerably across platforms, depending on whether external forces act directly on the object being assembled, or indirectly, through the medium where the assembly occurs, or both. Thrust 3’s proposed activities have been carefully conceived to address distinct and complementary elements of that coupling. The goals of Thrust 3 are to learn how to trigger well-defined responses in distinct elements of a nanoscale system, in a rational and predictable manner, and to demonstrate the corresponding principles in the creation of technologically relevant devices.
Context within the Center: The entire NSEC will benefit from supplementing directed assembly through application of external fields. The knowledge required to do so in a rational manner is developed under Thrust 3, and it is rapidly transferred to Thrusts 1 and 2 through targeted cross-Thrust projects, including theoretically-conceived strategies that seek to position nanoparticles and nanowires in structured copolymer melts (with Thrust 1) and that seek to interpret β-peptide assembly data at interfaces and through judicious application of electric fields (with Thrust 2), or that aim to create fully 3-dimensional structures by assembling complex DNA constructs on surfaces (with Thrust 2). Toxicity and environmental fate of synthesized nanoparticles is evaluated in Thrust 4.