Development of Magnetic Nanoparticles for Lateral Flow Assays using Atom Beam Lithography

We are developing a top-down method for forming magnetic nanoparticles from thin magnetic films, which allows us to tune the composition and the properties of the magnetic material using well-established physical vapor deposition techniques. The optimized particles are an important component of a larger project to develop an ultra-sensitive, quantifiable, low-cost diagnostic tool based on lateral flow technology, similar to home COVID tests. The use of a low-cost magnetometer for measuring the accumulated particle concentration will allow for rapid, point-of-care disease detection, and the technology serves as a platform for measuring the concentration of a variety of different markers. For this poster, we describe our manufacturing approach, which uses atom beam lithography to define the particle shape in a thin, polymer photoresist. After a development step, the particles remain as a relief in the polymer, and the shapes can be transferred to the magnetic film that is deposited below the polymer in advance. We have upgraded the lithography tool and have identified an epoxy-based photoresist that offers short exposure time, excellent fidelity, and high durability in the subsequent transfer steps. We demonstrate the formation of 300nm diameter disk-shaped structures in polymer that will serve as a high-quality masking layer for the particle patterning.