Microfabricated Particles Useful as MRI Contrast Agents

MRI contrast agents are versatile yet lack the sensitivity and multiplexing capabilities of optical agents. Available for licensing is an invention pertaining to microfabricated structures that can be used as MRI contrast agents with enhanced functionality or as micro-RFID (radio-frequency identification) tags. The microstructures can be engineered to appear as different effective colors when resolved using MRI as opposed to strictly grey-scale contrast of existing MRI agents. In this way they can be thought as radio-frequency analogs to quantum dots. A set of agents could be produced that would enable in vivo labeling and tracking of multiple different types of cells simultaneously. The agents can also act as radio-frequency probes of various physiological conditions. The invention can include a plurality of microstructures dispersed a liquid. The structures can have magnetic portions that vary in size, thickness and shape that are arranged to provide a substantially uniform Larmor precession frequency or a characteristic substantially uniform shift in Larmor precession frequency experienced by nuclear magnetic moments of a material when it is located in the substantially uniform field region created by the magnetic portions. In some embodiments, each of the nuclear magnetic resonance microstructures has a maximum dimension less than about 1 mm. The magnetic portions of the microstructure can be arranged proximate to each other, in contact with each other or be partially, substantially or totally coincident.