Browsing by Author "Zhao, Haoran"
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Item Control of Magnetic Robots: Solid Medium Transmission and Milli-Scale Magnetic Swimmer(2020-12) Zhao, Haoran; Becker, Aaron T.; Han, Zhu; Faghih, Rose T.; Ruchhoeft, Paul; Pan, Miao; Leclerc, JulienMagnetic robots show great potential for revolutionizing many aspects of medicine and clinical applications. The human body is transparent to a low-frequency magnetic field. Generally, a low frequency is considered less than 300 Hz. Magnetic resonance imaging (MRI) systems typically use a maximum slew rate of 200 mT/m/ms to limit the frequency. MRI is a powerful diagnostic modality for interventions and surgeries. However, MRIs are not used for performing interventions because the MRI has a very high magnetic field and is size constrained. The MRI opening is typically a cylinder that is 30cm in diameter and must accommodate a patient, gradient coils, and the MRI bed. This dissertation provides the design and implementation of a remotely-driven, MR-compatible robotic manipulator, and a force transmission mechanism for controlling that robot. Magnetism is also a promising modality for controlling robots. Magnetically actuated robots could perform minimally invasive surgery. Such robots could be employed for many clinical and biomedical applications, ranging from in vitro to in vivo applications of diagnosis and therapy. Part two of this dissertation examines the control, design optimization, and applications of a spiral shaped magnetic robot. The primary application is focused on blood clot removal. For clot removal, magnetic robots should be controlled and navigated in 3D environments. This requires control algorithms for high accuracy path-following in 3D fluidic environments. The dissertation provides frameworks, design concepts, and control theories for accurate control during blood clot removal. A further change for clot removal is that the clots are removed deep inside the human body. These areas are not visible to cameras, so control of the robots requires imaging techniques. This dissertation presents a process using an ultrasound scanner mounted on a six-axis robot arm to image and tracking the 6 mm long by 2.5 mm diameter magnetic swimmer as it moving in models of human vasculature.Item Simulation Pipeline of Milli-scale Magnetic Robots for Blood Clot Removal(2020-09-29) Ramos, Jocelyn; Lai, Joyce; Lu, YitongMilliscale, magnetically-controlled robots can be used for targeted blood clot removal. This method may provide a more precise, less dangerous, and less invasive removal process than the current methods which utilize blood thinning medication and catheters. These robots have helical threads so that magnetically induced rotation will produce a propulsive force that is controlled by an external magnetic system. The speed at which the robots need to rotate in order to hover in place in human blood is called the hovering frequency, and was used as a measure of the efficiency of the robot designs. We developed a pipeline for simulated testing of the robots using Finite Element Methods and post-processing. The flow of blood around the robots when rotating at various frequencies was modeled with the Navier-Stokes equations and approximated using the penalty method. In post-processing, the simulations were evaluated by visualizing the interaction of flow lines with the design geometries, confirming that the divergence is approximately zero along the geometry's surface, and calculating the generated propulsive forces. Various physical design parameters including thread depth, air pocket size, tip shape, and pitch, were tested with this method to compare the efficiency of hovering frequencies between simulated models. Future work will involve further optimization of the robot's shapes, evaluation of the model, and automation of the simulation process.