Miniature Magnetic Rotating Swimmers (MMRSs) are untethered machines containing magnetic materials. An external rotating magnetic field produces a torque on the swimmers to make them rotate. MMRSs have propeller fins that convert the rotating motion into forward propulsion. This type of robot has been shown to have potential applications in the medical realm. This paper presents new MMRS designs with (1) an increased permanent magnet volume to increase the available torque and prevent the MMRS from becoming stuck inside a thrombus; (2) new helix designs that produce an increased force to compensate for the weight added by the larger permanent magnet volume; (3) different head drill shape designs that have different interactions with thrombi. The two best MMRS designs were tested experimentally by removing a partially dried 1-hour-old thrombus with flow in a bifurcating artery model. The first MMRS disrupted a large portion of the thrombus. The second MMRS retrieved a small remaining piece of the thrombus. In addition, a tool for inserting, retrieving, and switching MMRSs during an experiment is presented and demonstrated. Finally, this paper shows that the two selected MMRS designs can perform accurate 3D path-following.

Rotating miniature magnetic swimmers are de-vices that could navigate within the bloodstream to access remote locations of the body and perform minimally invasive procedures. The rotational movement could be used, for example, to abrade a pulmonary embolus. Some regions, such as the heart, are challenging to navigate. Cardiac and respiratory motions of the heart combined with a fast and variable blood flow necessitate a highly agile swimmer. This swimmer should minimize contact with the walls of the blood vessels and the cardiac structures to mitigate the risk of complications. This paper presents experimental tests of a millimeter-scale magnetic helical swimmer navigating in a blood-mimicking solution and describes its turning capabilities. The step-out frequency and the position error were measured for different values of turn radius. The paper also introduces rapid movements that increase the swimmer's agility and demonstrates these experimentally on a complex 3D trajectory.

There are many design trade-offs when building a magnetic manipulator to control millimeter-scale rotating magnetic swimmers for surgical applications.For example, increasing the magnitude of the flux density generated by the magnetic manipulator increases the torque applied to the swimmer, which could enable performing a wider variety of surgical tasks in the future. However, producing stronger magnetic fields has drawbacks, such as increased active power usage.To produce a quickly rotating field, EMs must be quickly charged and discharged. This results in a low power factor (high reactive power used in comparison with the active power). Adding capacitors in series with the electromagnets improves the power factor because the capacitors can provide reactive power. With this method, larger flux densities can be produced without necessitating an increase of the apparent power delivered by the power supplies.This paper highlights the benefits of using capacitors for the magnetic manipulation of rotating swimmers. Rotating swimmers can be used to remove blood clots. The clot removal rate of resonating magnetic manipulators is measured using a realistic blood clot model. This paper also presents a control method for the currents inside the electromagnets that enable 3D navigation without current sensing.