Doctor of Philosophy

dissertationThis dissertation explores the design and use of an electromagnetic manipulation system that has been optimized for the dipole-eld model. This system can be used for noncontact manipulation of adjacent magnetic tools and combines the eld strength control of current electromagnetic systems with the analytical modeling of permanent-magnet systems. To design such a system, it is rst necessary to characterize how the shape of the eld source aects the shape of the magnetic eld. The magnetic eld generated by permanent magnets and electromagnets can be modeled, far from the source, using a multipole expansion. The error associated with the multipole expansion is quantied, and it is shown that, as long as the point of interest is 1.5 radii of the smallest sphere that can fully contain the magnetic source, the full expansion will have less than 1% error. If only the dipole term, the rst term in the expansion, is used, then the error is minimized for cylindrical shapes with a diameter-to-length ratio of 4=3 and for rectangular-bars with a cube. Applying the multipole expansion to electromagnets, an omnidirectional electromagnet, comprising three orthogonal solenoids and a spherical core, is designed that has minimal dipole-eld error and equal strength in all directions. Although this magnet can be constructed with any size core, the optimal design contains a spherical core with a diameter that is 60% of the outer dimension of the magnet. The resulting magnet's ability to dextrously control the eld at a point is demonstrated by rotating an endoscopic-pill mockup to drive it though a lumen and roll a permanent-magnet ball though several trajectories. Dipole elds also apply forces on adjacent magnetized objects. The ability to control these forces is demonstrated by performing position control on an orientation-constrained magnetic oat and nally by steering a permanent magnet, which is aligned with the applied dipole eld, around a rose curve

Capsule endoscopy of the future: What's on the horizon?

Capsule endoscopes have evolved from passively moving diagnostic devices to actively moving systems with potential therapeutic capability. In this review, we will discuss the state of the art, define the current shortcomings of capsule endoscopy, and address research areas that aim to overcome said shortcomings. Developments in capsule mobility schemes are emphasized in this text, with magnetic actuation being the most promising endeavor. Research groups are working to integrate sensor data and fuse it with robotic control to outperform today's standard invasive procedures, but in a less intrusive manner. With recent advances in areas such as mobility, drug delivery, and therapeutics, we foresee a translation of interventional capsule technology from the bench-top to the clinical setting within the next 10 years

Doctor of Philosophy

dissertationThis dissertation presents results documenting advancements on the control of untethered magnetic devices, such as magnetic \microrobots" and magnetically actuated capsuleendoscopes, motivated by problems in minimally invasive medicine. This dissertationfocuses on applying rotating magnetic elds for magnetic manipulation. The contributions include advancements in the way that helical microswimmers (devices that mimicthe propulsion of bacterial agella) are controlled in the presence of gravitational forces, advancements in ways that groups of untethered magnetic devices can be dierentiated and semi-independently controlled, advancements in the way that untethered magnetic device can be controlled with a single rotating permanent magnet, and an improved understanding in the nature of the magnetic force applied to an untethered device by a rotating magnet