Onder Erin

Miniaturization of medical tools promises to revolutionize surgery by reducing tissue trauma and accelerating recovery. Magnetic untethered devices, with their ability to access hard-to-reach areas without physical connections, emerge as potential candidates for such miniaturization. Despite the benefits, these miniature devices face challenges regarding force and torque outputs, restricting their ability to perform tasks requiring mechanical interactions such as tissue penetration and manipulation. To overcome magnetic actuation system-based force and torque limitations, this study proposes Variable Outer Radius Individually Addressable Coil Stacks (VORIACS), a novel magnetic actuation system optimized for high force output generation to magnetic devices within its workspace. The VORIACS marks significant improvements and breakthroughs in magnetic actuation within decimeter-scale workspace. The VORIACS is comprised of 12 coils that are optimized for 2D magnetic field generation under maximized power consumption of up to 12 kW. We implement six two-channel motor controllers, powered by six separate power supplies. Each of the twelve coils in the system is operated on its own motor-controller channel. This arrangement allows the system to exceed the magnetic forces and torques possible for single-coil versions of the same geometry. This study elaborates on optimizing, manufacturing, integrating, and demonstrating this system. Comparative analysis reveals that while a suboptimal, single-coil version of this system generates 0.31 N force (710 mT/m magnetic gradient magnitude), the VORIACS produces 1.673 N force (3834 mT/m magnetic gradient magnitude) on the same magnetic object placed 5 cm away from the coils. Moreover, the strong penetration force generated by VORIACS enables needle penetration to a mock gel that has the rigidity of liver tissue. In addition, we demonstrate the advantage of stacked coils with variable radii for magnetic field manipulability while maintaining the optimized force delivery property of the system, which improves control and could facilitate multi-tool manipulation. By enabling a fivefold increase in magnetic pulling force compared to its single-coil counterpart, VORICAS raises the potential penetration capabilities of untethered magnetic robotics in surgical procedures.

Efforts to develop an artificial intestine for treatment of short bowel syndrome have thus far failed to achieve coordinated peristalsis. To address this, we introduce an implantable, biomimetic, magnetically-actuated peristaltic pumping apparatus. The system consists of a magnetic pump surrounding an intestinal graft and a rotating external magnetic field generator that produces peristaltic motion in the graft as the field direction alternates. We performed computational finite element modeling to simulate deformation and stress concentration on the pump. We then tested the ability of the system to produce fluid flow through porcine subintestinal submucosa at actuation frequencies from 0 Hz to 4 Hz. The system achieved a maximal flow rate of 6.03 mL/min at 3 Hz actuation frequency, which is in the physiological range of human intestinal flow rates. This device represents a novel proof-of-concept for achieving untethered peristalsis in an implantable intestinal graft that is primed for preclinical testing in animal models of short bowel syndrome.

Magnetic actuation systems that utilize external electromagnetic coils present a promising approach for controlling untethered small-scale robots, notably in medical applications. However, these systems frequently experience actuation singularities at which robotic control over the agent is lost or severely diminished. Such singularities may lead to excessively large current or rapid current changes that significantly affect the robots’ stability in specific areas of the workspace. In order to effectively mitigate these actuation singularities, this paper introduces a closed-loop control method using a novel nested electromagnetic coil system, leveraging finite element analysis-based magnetic field data and a novel controller combining a singularity solver and optimal current control method. The electromagnetic system has 12 coils nested in four coil units, each having three concentric coils with different outer radius, surrounding a central workspace. We call the 12-coil system Variable Outer Radius Individually Addressable Coil Stacks (VORIACS). Here, we experimentally evaluate the method for closed-loop trajectory tracking of a soft magnetic capsule endoscope (PillCam™) and a permanent magnet robot inside the VORIACS system at different magnetic field orientations. The results demonstrate that the VORIACS system with a singularity solver reduces root mean square (RMS) position tracking errors of the PillCam™by 46% to 50% and orientation tracking errors by 41% to 42% compared to a standard 4-coil system. Moreover, the system can achieve a notable 60.73% reduction in RMS position error, with sub-millimeter precision control when controlling the permanent magnet robot. We further manipulate the PillCam™for tracking a medical application-inspired complex trajectory, showcasing the system’s potential in precise control of magnetic devices for medical use.

The evolution of magnetically actuated millirobots gives rise to unique teleoperation challenges due to their non-traditional kinematic and dynamic architectures, as well as their frequent use of suboptimal imaging modalities. Recent investigations into haptic interfaces for millirobots have shown promise but lack the clinically motivated task scenarios necessary to justify future development. In this work, we investigate the utility of haptic feedback on bilateral teleoperation of a magnetically actuated millirobot in visually deficient conditions. We conducted an N = 23 user study in an aneurysm coiling inspired procedure, which required participants to navigate the robot through a maze in near total darkness to manipulate beads to a target under simulated fluoroscopy. We hypothesized that users will be better able to complete the telemanipulation task with haptic feedback while reducing excess forces on their surroundings compared to the no feedback conditions. Our results showed an over 40% improvement in participants' bead scoring, a nearly 10% reduction in mean force, and 13% reduction in maximum force with haptic feedback, as well as significant improvements in other metrics. Results highlight that benefits of haptic feedback are retained when haptic feedback is removed. These findings suggest that haptic feedback has the potential to significantly improve millirobot telemanipulation and control in traditionally vision deficient tasks.

Magnetically manipulated medical robots are a promising alternative to current robotic platforms, allowing for miniaturization and tetherless actuation. Controlling such systems autonomously may enable safe, accurate operation. However, classical control methods require rigorous models of magnetic fields, robot dynamics, and robot environments, which can be difficult to generate. Model-free reinforcement learning (RL) offers an alternative that can bypass these requirements. We apply RL to a robotic magnetic needle manipulation system. Reinforcement learning algorithms often require long runtimes, making them impractical for many surgical robotics applications, most of which require careful, constant monitoring. Our approach first constructs a model-based simulation (MBS) on guided real-world exploration, learning the dynamics of the environment. After intensive MBS environment training, we transfer the learned behavior from the MBS environment to the real-world. Our MBS method applies RL roughly 200 times faster than doing so in the real world, and achieves a 6 mm root-mean-square (RMS) error for a square reference trajectory. In comparison, pure simulation-based approaches fail to transfer, producing a 31 mm RMS error. These results demonstrate that MBS environments are a good solution for domains where running model-free RL is impractical, especially if an accurate simulation is not available.

Magnetic actuation holds promise for wirelessly controlling small, magnetic surgical tools and may enable the next generation of ultra minimally invasive surgical robotic systems. Precise torque and force exertion are required for safe surgical operations and accurate state control. Dipole field estimation models perform well far from electromagnets but yield large errors near coils. Thus, manipulations near coils suffer from severe (10x) field modeling errors. We experimentally quantify closed-loop magnetic agent control performance by using both a highly erroneous dipole model and a more accurate numerical magnetic model to estimate magnetic forces and torques for any given robot pose in 2D. We compare experimental measurements with estimation errors for the dipole model and our finite element analysis (FEA) based model of fields near coils. With five different paths designed for this study, we demonstrate that FEA-based magnetic field modeling reduces positioning root-mean-square (RMS) errors by 48% to 79% as compared with dipole models. Models demonstrate close agreement for magnetic field direction estimation, showing similar accuracy for orientation control. Such improved magnetic modelling is crucial for systems requiring robust estimates of magnetic forces for positioning agents, particularly in force-sensitive environments like surgical manipulation.

The application of force in surgical settings is typically accomplished via physical tethers to the surgical tool. While physical tethers are common and critical, some internal surgical procedures may benefit from a tetherless operation of needles, possibly reducing the number of ports in the patient or the amount of tissue damage caused by tools used to manipulate needles. Magnetic field gradients can dynamically apply kinetic forces to magnetizable objects free of such tethers, possibly enabling ultra-minimally invasive robotic surgical procedures. We demonstrate the untethered manipulation of a suture needle in vitro, exemplified by steering through narrow holes, as well as needle penetration through excised rat and human tissues. We present proof of principle manipulations for the fully untethered control of a minimally modified, standard stainless steel surgical suture needle.

Magnetic resonance imaging (MRI)-powered magnetic robotics aims to convert clinical MR scanners into a remote robotic manipulation platform to provide an alternative approach for interventional MRI procedures. The presence of the main magnetic field ( B ₀ ) inside of MRI systems imposes magnetic constraints. Because of this static and strong magnetic field, many magnetic actuation techniques to orient or rotate magnetic objects are not feasible under MRI. Therefore, the robot design and actuation methods should consider these constraints for the intended medical applications. A free-to-rotate robot design could be utilized under MRI for providing rotational motion with magnetic pulling. However, the coupled translation with rotation induces difficulty in control of these robots, especially for camera pointing towards capsule endoscopy. In this study, we present a wireless magnetic robot that exploits a surface contact to create a rotation around a contact point with minimal translation. The proposed robot is integrated with a camera and an on-board battery for endoscopy purposes. The robot's tuned density also allows three-dimensional (3D) navigation to visually scan the workspace. We also demonstrate the open- and closed-loop actuation and control performance to explore the range of pitch angles accomplishable and closed-loop feedback control accuracy by using visual feedback. The closed-loop control experiments have shown 0.19 ^° of steady-state error with 1.9 seconds rise time and 20% overshoot. Thanks to the surface contact during orientation control, the worst-case undesired translation is found to be 6.7 mm. Such robot provides the first steps towards active capsule endoscopy actuated by MRI devices for combining physiological images from an MRI device and the auxiliary visual camera images via the capsule robot to diagnose certain diseases in the gastrointestinal (GI) tract.

Magnetic resonance imaging (MRI) scanners do not provide only high‐resolution medical imaging but also magnetic robot actuation and tracking. However, the rotational motion capabilities of MRI‐powered wireless magnetic capsule‐type robots have been limited due to the very high axial magnetic field inside the MRI scanner. Medical functionalities of such robots also remain a challenge due to the miniature robot designs. Therefore, a wireless capsule‐type reversible orientation‐locking robot (REVOLBOT) is proposed that has decoupled translational motion and planar orientation change capability by locking and unlocking the rotation of a spherical ferrous bead inside the robot on demand. Such an on‐demand locking/unlocking mechanism is achieved by a phase‐changing wax material in which the ferrous bead is embedded inside. Controlled and on‐demand hyperthermia and drug delivery using wireless power transfer‐based Joule heating induced by external alternating magnetic fields are the additional features of this robot. The experimental feasibility of the REVOLBOT prototype with steerable navigation, medical function, and MRI tracking capabilities with an 1.33 Hz scan rate is demonstrated inside a preclinical 7T small‐animal MRI scanner. The proposed robot has the potential for future clinical use in teleoperated minimally invasive treatment procedures with hyperthermia and drug delivery capabilities while being wirelessly powered and monitored inside MRI scanners.

Wireless powering of magnetoelectric nanoelectrodes is used for deep brain stimulation in freely moving and transgene-free mice.