Characterizing Field-Dependent Strength and Orientation of Superparamagnetic Bead Magnetization Via DNA Origami Microlevers

Many advancements in biomedical and nanotechnologies have been realized through the ability to precisely control the spatial and temporal movement of micro- and nano-actuators using superparamagnetic beads. Despite the range of applications, the nature of the magnetization of the MyOne Dynabeads has not been fully investigated. To quantify the torque on superparamagnetic beads in precessing external magnetic fields, it is important to understand how the individual magnetic dipoles within a bead respond to the changing magnetic fields. This research establishes a novel approach to investigate the field-dependent magnetization of individual MyOne Dynabeads for external fields between 10 Oe to 100 Oe. To overcome the challenges of tracking the movement of single beads, the bead is tethered to the surface through attachment to a stiff DNA microrod which is assembled using the DNA origami technique. By applying in-plane external fields to the DNA-rod tethered beads, the strength and orientation of the magnetization can be determined from the response and thermal fluctuations of the bead. Preliminary results show that there are two contributing factors to the net magnetic moment: the permanent moment which dominates at lower fields, and the induced anisotropic component which dominates at higher fields.