Synthetic Antiferromagnetic Designer Nanodisks for High-Performance Magnetic Separation

Magnetic separation of magnetic particles offers an appealing route to rapid and selective target capturing and isolation. However, to leverage such an approach to its full potential, high colloidal stability of the nanoparticles in the absence of a magnetic field for optimal binding, and rapid and quantitative recovery upon magnetic gradient field application are imperative. While these properties are mutually exclusive for conventional nanoparticles synthesized by wet-chemistry approaches, sputter deposition gives access to layered architectures featuring the properties of a synthetic antiferromagnet (SAF, no magnetization in zero field, high magnetization upon field application). Here, micromagnetic-modelling based design optimization and scalable manufacturing of metallic CoSm-based, metal oxide-capped SAF magnetic disk particles (SAF MDPs) with high chemical and colloidal stability and cytocompatibility are presented. It is demonstrated that the SAF MDPs can be rapidly and much more efficiently separated ( $>99\%$ ) from flowing fluids (approx. 1 mL/min) compared to corresponding gold standard iron oxide beads ( $60\%$ recovery), paving the way to quantitative capturing and enrichment of target compounds in high-throughput conditions compliant with clinical and industrial applications.