Continuous Acoustic Assembly of Metallic Nanoparticles in Microfluidic Systems

Duke University, Durham NC

Investigators

Abstract

This project will exploit the wealth of functional metallic nanoparticles developed over the last two decades by providing new continuous nanomanufacturing methods for directed assembly of nanoparticles into well-defined, multicomponent and multifunctional nanoclusters. The broad goal of this work is to develop a suite of new manufacturing tools for the scalable, continuous production of regular assemblies of metallic nanoparticles that are either spherical or polyhedral in shape. Directed assembly will be accomplished through the use of ultrasonic waves to pack nanoparticles together (acoustophoresis), after which the nanoparticles will organize into highly regular, packed structures to maximize the number of energy states available to individual nanoparticles (entropic assembly). An advantage of this method is reducing contamination. This work will develop the fundamental underpinnings of continuous nanoparticle assembly and translate them into prototype manufacturing processes. These processes will be capable of fabricating high-value products for a number of applications including medicine, biotechnology, photonics, catalysis, and security (anti-counterfeiting measures). To demonstrate the impact of this new technology, this project will create well-defined, multifunctional nanoclusters for high performance applications such as drug delivery and bioimaging. The fabrication of nanoparticle assemblies will be accomplished in microfluidic systems that include ultrasonic standing waves to achieve acousto-entropic assembly of the nanoparticles and photochemical crosslinking reactions to covalently stabilize the physically assembled clusters. To achieve these aims, several key tasks will be completed--(i) study of the fundamental processes leading to continuous acoustic and entropic assembly of nanoparticles, (ii) surface modification of the nanoparticles to allow multi-functionality, including colloidal stability, ligand and dye binding, and triggered crosslinking, (iii) development of new metrology tools that permit process optimization to maximize throughput, yield and purity, and (iv) study of model nanoparticle assemblies that have useful, multimodal functionalities in drug delivery and bioimaging to maximize the scientific and societal impact of acousto-entropic nanoparticle assembly. This research program will include basic studies to demonstrate new manufacturing principles that are unique to nanoscale phenomena, such as entropic assembly of particles in the absence of confining solid boundaries, while at the same time overcoming technical barriers, such as enhancement of the mass transfer limited kinetics typically associated with nanoparticle assembly. This project will also provide several innovations in manufacturing technology including continuous and scalable production of well defined nanoparticle assemblies in the form of heterogeneous particles, rods and filaments, as well as new nanomanufacturing process control methodologies based on acoustic impedance spectroscopy and laser light scattering.