An official website of the United States government
Millimeter-scale magnetic rotating swimmers have multiple potential medical applications. They could, for example, navigate inside the bloodstream of a patient toward an occlusion and remove it. Magnetic rotating swimmers have internal magnets and propeller fins with a helical shape. A rotating magnetic field applies torque on the swimmer and makes it rotate. The shape of the swimmer, combined with the rotational movement, generates a propulsive force. Visual feedback is suitable for in-vitro closed-loop control. However, in-vivo procedures will require different feedback modalities due to the opacity of the human body. In this paper, we provide new methods and tools that enable the 3D control of a magnetic swimmer using a 2D ultrasonography device attached to a robotic arm to sense the swimmer’s position. We also provide an algorithm that computes the placement of the robotic arm and a controller that keeps the swimmer within the ultrasound imaging slice. The position measurement and closed-loop control were tested experimentally.
more »
« less
Open-Source CFD Simulation of Magnetic Rotating Swimmers with Experimental Validation
Many potential medical applications for magnetically controlled tetherless devices inside the human body have been proposed, including procedures such as biopsies, blood clot removal, and targeted drug delivery. These devices are capable of wirelessly navigating through fluid-filled cavities in the body, such as the vascular system, eyes, urinary tract, and ventricular system, to reach areas difficult to access via conventional methods. Once at their target location, these devices could perform various medical interventions. This paper focuses on a special type of magnetic tetherless device called a magnetic rotating swimmer, which has internal magnets and propeller fins with a helical shape. To facilitate the design process, an automated geometry generation program using OpenSCAD was developed to create the swimmer design, while computational fluid dynamics simulations using OpenFOAM were employed to calculate the propulsive force produced by the swimmer. Furthermore, an experimental approach is proposed and demonstrated to validate the model. The results show good agreement between simulations and experiments, indicating that the model could be used to develop an automatic geometry optimization pipeline for rotating swimmers.
more »
« less
- PAR ID:
- 10552105
- Publisher / Repository:
- IEEE
- Date Published:
- ISBN:
- 979-8-3503-5851-3
- Page Range / eLocation ID:
- 3779 to 3784
- Subject(s) / Keyword(s):
- Robotics magnetic CFD
- Format(s):
- Medium: X
- Location:
- Bari, Italy
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
null (Ed.)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.more » « less
-
Microorganisms are commonly found swimming in complex biological fluids such as mucus and these fluids respond elastically to deformation. These viscoelastic fluids have been previously shown to affect the swimming kinematics of these microorganisms in non-trivial ways depending on the rheology of the fluid, the particular swimming gait and the structural properties of the immersed body. In this report we put forth a previously unmentioned mechanism by which swimming organisms can experience a speed increase in a viscoelastic fluid. Using numerical simulations and asymptotic theory we find that significant swirling flow around a microscopic swimmer couples with the elasticity of the fluid to generate a marked increase in the swimming speed. We show that the speed enhancement is related to the introduction of mixed flow behind the swimmer and the presence of hoop stresses along its body. Furthermore, this effect persists when varying the fluid rheology and when considering different swimming gaits. This, combined with the generality of the phenomenon (i.e. the coupling of vortical flow with fluid elasticity near a microscopic swimmer), leads us to believe that this method of speed enhancement could be present for a wide range of microorganisms moving through complex fluids.more » « less
-
Abedin-Nasab, Mohammad Hossein (Ed.)A pulmonary embolism is a blood clot that develops in a blood vessel (often in the leg) and then travels to a lung artery, where it suddenly blocks blood flow. A miniature magnetic rotating swimmer (MMRS) is a device with internal magnets and propeller fins. It can be steered by an external rotating magnetic field. The shape of the swimmer combined with the rotational movement can generate a propulsive force to move the swimmer to the target location, abrading blood clots using the rotational motion. This chapter presents the MMRS’s design and fabrication, thrombi disruption performance, and 3D path-following capability. Algorithms that enable controlling a swimmer in 3D using a 2D ultrasonography device are presented. A tool that can deliver and retrieve the MMRS for thrombi disruption is demonstrated.more » « less
-
Compliance is desirable in an undulatory swimming robot due to potential increases in thrust and propulsive efficiency. However, soft body dynamics are challenging to control, being characteristically nonlinear and possessing many degrees of freedom. Control of soft swimmers is further complicated by coupling between the dynamics of the swimmer body, the dynamics of the soft actuators, and the dynamics of the surrounding fluid, which are also highly nonlinear. We predict the hydrodynamic forces acting on a soft swimmer with physical reservoir computing, which can leverage the complex dynamics of the fluid-swimmer system to perform real-time computations. In our implementation, only the internal pressures of our swimmer’s soft hydraulic actuators are taken as reservoir readouts, permitting a fully compliant design. To evaluate this strategy and identify areas of future development, we examine the predictive performance for thrust, heave force, and yaw moment in steady swimming across a range of excitation frequencies and body stiffnesses. Our results show that using the internal actuator pressures as readouts enables accurate prediction for linear tasks, where the target does not contain significant nonlinear features. However, these readouts limit the predictive performance of the approach for nonlinear tasks, including some undulatory swimming state estimation tasks.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Conference Paper:
- https://doi.org/10.1109/CASE59546.2024.10711422
