Roll-Imprint Manufacturing of Three-Dimensional Nanomagnetic Arrays

This grant promotes the progress of science by exploring the fundamental design principles behind the roll-imprint process for manufacturing nanomagnetic arrays for a wide range of applications, including individualized nanomedicine and radar thus advancing national health, prosperity and security. Current nanomedicine uses magnetic iron oxide nanoparticles in bio-labels for cancer diagnosis and therapy and for magnetic resonance imaging (MRI). Magnetic thin films are promising in circulators that block reflections from re-entering radar sources, hence eliminating noise and enhancing performance. This project disrupts both of these diverse technologies using three dimensional (3D) nanomagnetic arrays. The arrays are essentially groupings of barcoded nanowires that can be visualized as the pelt of a porcupine - shrunk to fit on the tip of a pen. Individually, the 'quills' are so small that they are internalized by cells, leading to effective cellular barcoding. As an array, or 'pelt', the quill or nanowire assembly acts like a one-way mirror for radar signals. The manufacturing process developed here enables rolls of 3D nanomagnetic arrays to be produced with a yield of one billion nanowires per minute. Undergraduate and graduate student training by two female electrical engineers supports education and diversity and enables students to conduct research in medical diagnosis and radar for self-driving cars for the benefit of society.

Fundamental design principles are established for roll-imprint manufacturing of three dimensional (3D) nanomagnetic arrays, including nanostructure design, process design, and quality control design. Two underlying testbeds, radio-frequency identification (RFID) bio-labels and high frequency circulators for self-driving cars, are used to verify the designs. For nanostructure design, hierarchical nanostructures are composed of zero dimensional (0D) nanodisks stacked into one-dimensional (1D) nanowires that are inside two-dimensional (2D) arrays of columnar nanopores to make three-dimensional (3D) structures. The magnetic spin structures are simulated to facilitate design with experimental verification. The process design involves roll-imprinting of aluminum before anodization to produce aluminum oxide templates containing columnar nanopores with long range order. Electrodeposition is then used to fill these nanopores with single component ferromagnetic metals and multilayers according to the desired nanostructure designs. Quality control design involves high frequency circuits, including coplanar waveguides to measure ferromagnetic resonance and custom designed circulators to measure composite properties. Importantly, the quality control design is directly applicable for testbed success. Previous work has successfully demonstrated 3D nanomagnetic arrays that were synthesized using planar components with areas of square-centimeter. This work scales up manufacturing to square-meter per hour rates in a step-continuous roll-to-roll process.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.