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With remote magnetic steering capabilities, magnetically actuated guidewires have proven their potential in minimally invasive medical procedures. Existing magnetic steering strategies, however, have been limited to low magnetic fields, which prevents the integration into medical systems operating at ultrahigh fields (UHF), such as magnetic resonance imaging (MRI) scanners. Here, we present magnetic guidewire design and steering strategies by elucidating the magnetic actuation principles of permanent magnets at UHF. By modeling the uniaxial magnetization behavior of permanent magnets, we outline the magnetic torque and force and demonstrate unique magnetic actuation opportunities at UHF, such as in situ remagnetization. Last, we illustrate the proposed steering principles using a magnetic guidewire composed of neodymium magnets and a fiber optic rod in a 7-Tesla preclinical MRI scanner. The developed UHF magnetic actuation framework would enable nextgeneration magnetic robots to operate inside MRI scanners., Science Advances, 9 (17), ISSN:2375-2548

Magnetic resonance imaging (MRI)-tuned radio-frequency (RF) sensors are used as a radiation-free alternative for tracking minimally invasive medical tool positions. However, in situ temperature sensing capabilities of the MRI-tuned RF sensors have not been thoroughly investigated yet. A self-resonating RF sensor capable of remote in situ temperature sensing during real-time interventional MRI is presented. The proposed RF sensor design relies on the temperature-dependent permittivity to tune or detune the resonant frequency. The sensor is tuned to match the resonant frequency of a 7 Tesla MRI (298 MHz) at body temperature, enabling a hyperintense signal in MR images. As temperature increases, the sensor detunes due to the change in the relative permittivity, and the hyperintense signal disappears in the MR image, serving as a direct visual indicator of the temperature change in real-time. In addition, the localized signal can be used for 3D position tracking of interventional medical devices. Using a 7 Tesla preclinical MRI, in vitro characterization and ex vivo feasibility of the proposed temperature sensing method are demonstrated in the clinically relevant temperature range of 36–42 °C with an accuracy of ±0.6 °C. Such RF sensors can provide safer operations in future MRI interventional procedures., Advanced Materials Technologies, 7 (9), ISSN:2365-709X

Controlled microrobotic navigation in the vascular system can revolutionize minimally invasive medical applications, such as targeted drug and gene delivery. Magnetically controlled surface microrollers have emerged as a promising microrobotic platform for controlled navigation in the circulatory system. Locomotion of micrororollers in strong flow velocities is a highly challenging task, which requires magnetic materials having strong magnetic actuation properties while being biocompatible. The L1(0)-FePt magnetic coating can achieve such requirements. Therefore, such coating has been integrated into 8 mu m-diameter surface microrollers and investigated the medical potential of the system from magnetic locomotion performance, biocompatibility, and medical imaging perspectives. The FePt coating significantly advanced the magnetic performance and biocompatibility of the microrollers compared to a previously used magnetic material, nickel. The FePt coating also allowed multimodal imaging of microrollers in magnetic resonance and photoacoustic imaging in ex vivo settings without additional contrast agents. Finally, FePt-coated microrollers showed upstream locomotion ability against 4.5 cm s(-1) average flow velocity with real-time photoacoustic imaging, demonstrating the navigation control potential of microrollers in the circulatory system for future in vivo applications. Overall, L1(0)-FePt is conceived as the key material for image-guided propulsion in the vascular system to perform future targeted medical interventions., Advanced Functional Materials, 32 (8), ISSN:1616-3028, ISSN:1616-301X

Electromagnetic field gradients generated by magnetic resonance imaging (MRI) devices pave the way to power untethered magnetic robots remotely. This innovative use of MRI devices allows exerting magnetic pulling forces on untethered magnetic robots, which could be used for navigation, diagnosis, drug delivery and therapeutic procedures inside a human body. So far, MRI-powered untethered magnetic robots lack simultaneous position and orientation control inside three-dimensional (3D) fluids, and therefore, their control has been limited to 3-DoF position control. In this paper, we present a path-planning-based 5-DoF control algorithm to steer and control an MRI-powered untethered robot’s position and orientation simultaneously in 3D workspaces in fluids. Eventhough the simulation results show that the proposed optimal controller can successfully control the robot for 5-DoF, in the experiments, we observe a reduced 5-DoF controllability due to the robot manufacturing errors, which result in pitch angle to remain at around the neutral pitching angle at the steady state. The proposed controller was evaluated to track four different paths (linear, planar-horizontal, planar-vertical and 3D paths) generated by 3D Bezier curves. The worst-case path-tracking error was observed for 3D path-following experiments. For this case, the position-tracking error was 2.7±1.8 mm, and the orientation-tracking error was 13.5± 28.7 and 3.7± 10.2 degrees for yaw and pitch angles, respectively. The overall path is completed within 19.6 seconds with 23.6 mm overall displacement and 61.2 and 41.2 degrees of yaw and pitch angle rotation, respectively. Such robots can be used in future MRI-powered active imaging, laser surgery and biopsy robots inside a fluid-filled stomach type of organs.

Building and Construction have recently become an exciting application ground for robotics. In particular, rapid progress in materials formulation and in robotics technology has made robotic 3D Printing of concrete a promising technique for in-situ construction. Yet, scalability remains an important hurdle to widespread adoption: the printing systems (gantry- based or arm-based) are often much larger than the structure to be printed, hence cumbersome. Recently, a mobile printing system - a manipulator mounted on a mobile base - was proposed to alleviate this issue: such a system, by moving its base, can potentially print a structure larger than itself. However, the proposed system could only print while being stationary, imposing thereby a limit on the size of structures that can be printed in a single take. Here, we develop a system that implements the printing-while-moving paradigm, which enables printing single-piece structures of arbitrary sizes with a single robot. This development requires solving motion planning, localization, and motion control problems that are specific to mobile 3D Printing. We report our framework to address those problems, and demonstrate, for the first time, a printing-while-moving experiment, wherein a 210 cm x 45 cm x 10 cm concrete structure is printed by a robot arm that has a reach of 87 cm., 6 pages, 7 figure

Being motivated by ceiling inspection applications via unmanned aerial vehicles (UAVs) which require close proximity flight to surfaces, a systematic control approach enabling safe and accurate close proximity flight is proposed in this work. There are two main challenges for close proximity flights: (i) the trust characteristics varies drastically for the different distance from the ceiling which results in a complex nonlinear dynamics; (ii) the system needs to consider physical and environmental constraints to safely fly in close proximity. To address these challenges, a novel framework consisting of a constrained optimization-based force estimation and an optimization-based nonlinear controller is proposed. Experimental results illustrate that the performance of the proposed control approach can stabilize UAV down to 1 cm distance to the ceiling. Furthermore, we report that the UAV consumes up to 12.5% less power when it is operated 1 cm distance to ceiling, which is promising potential for more battery-efficient inspection flights., Comment: Accepted to IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2019)