The ultimate goal of this collaborative research project is to test the hypothesis that magnetic recording can be used to direct the assembly of nanomaterials into complex 2D and 3D structures, and offers a promising route towards rapid and low-cost nanomanufacturing. The approach is to use magnetic recording media (i.e. platters found in modern hard drives) to direct the assembly of magnetic nanoparticles. A thin polymeric film is then coated onto the surface, and the deposited particles are lifted off while maintaining this written pattern. This transformative approach to nanomanufacturing employs nanoscale forces from magnetically-recorded patterns to assemble nanoparticles from a carrier fluid into de-signed nanostructures on the surface of a disk drive platter. The nanoparticle assembly is then spin-coated with a polymer and the matrix is peeled from the disk surface, transferring the nanoscale patterns to a flexible, transparent film. While this concept has been demonstrated, key challenges to commercializing it remain. Control of this concept will be extended by understanding how the assembly depends on the raw nanomaterials: nanoparticle shape, size, magnetic moment, and surface functionalization, in addition to the kinetics of the fluidic assembly process, variances in nanoscale positioning, and the fundamental limits of the recording process. This collaborative project is structured to allow continuous feedback between process and raw materials to build stability needed for commercial launch. In addition, novel extensions will be explored that add functionality, including assembly of different nanoparticle species within a single layer, and combining multiple layers and films into more complex, nanostructured materials. To accomplish these goals the project is divided into three main task groups: 1. Nanoparticle synthesis and assembly interaction control, 2. Assembly and metrology below 100 nm size scales, and 3. Directed assembly of complex systems, plus an additional group focused on collaborative education and outreach. These components focus on overcoming key roadblocks to the technology's scalability, developing the tools for processing and process metrology, and creating novel, complex systems to increase commercial relevance.
This project will build understanding of this undeveloped technology to assess and overcome the major hurdles to implementation in a manufacturing environment. By optimizing commercial magnetic recording for bottom-up nanostructure assembly, an innovative class of inexpensive techniques will be available to the wider nanotechnology community for manufacturing new devices, including optoelectronic components, novel biomaterials, and materials for future energy technologies. Given the scale and cost at which magnetic recording components are presently manufactured, the leverage to succeed in scaling this approach to commercial nanomanufacturing is tremendous. The opportunity to apply current technology to enable future manufacturing, combined with understanding the community structures which inhibit nano-commercialization, offers a unique and broad educational experience for the project researchers. Students at both USC and Clemson, the primary research universities in South Carolina, will participate through a recently piloted course that develops a technical and historical perspective on manufactured technologies, to foster innovation and create new ones.
Supported by CMMI 1130636/1130819, Crawford and Mefford focused on the fundamentals of tailored iron oxide nanoparticle synthesis, formation of linear structures for diraction,and real-time monitoring of the assembly process. In other words, the collaborative team created unique building block materials and developed new techniques to assemble and monitor the assembly of the particles on a nanometer scale. This project has resulted in: 7 peer reviewed articles. 1 invention disclosure 3 contributed oral talks and a poster. 2 Ph.D. students in Materials Science defended their dissertations 2 REU undergraduate summer researchers were supported 2 additional undergraduate researchers. Production of novel multifunctional nanoparticles through investigation of reaction conditions Demonstration the nanomanufacturing of a concave polymer diffraction grating using PTNM. ``Real-time" observation of nanomanufacturing, by monitoring the formation of a nanoparticle diffraction grating, was developed. Development of new techniques for accelerating or slowing the assembly process were discovered, where assembly can be turned on or off by altering the nanoparticle suspension properties, providing a novel window for modifying nanoparticle stability to optimize magnetic-field directed self assembly. Crawford and Mefford together assembled a briefcase demonstration kit for showing lay audiences the nanomanufacturing technology that included the ability to view optical diraction from a diraction grating built with PTNM. Crawford and one of Mefford's Ph.D. students performed these demonstrations over 2 days at a booth at a local innovation conference, Innoventure, held in Greenville, SC in May 2013. In addition, this briefcase was used as part of PI Mefford's honors introduction to nanotechnology class, where students magnetically assembled particles they synthesized in class. Also, 7 undergraduates and four graduate students, two of them women, learned how to perform the PTNM process. The work has lead to a novel way to make a concave all-nanoparticle diraction grating as well as a new real-time in-situ process metrology for manufacturing verication that is based on the strong sensitivity of optical diraction. The diraction measurement could be a complement to conventionally used dynamic light scattering for nanoparticle studies.
