Electromagnetic Manipulation System Research Articles

Selection of functional sperm by using hyaluronic acid modified magnetic microbeads and an electromagnetic manipulation system.

In recent years, the incidence of infertility has increased year by year. Assisted reproductive technology (ART) is one of the effective strategies to treat infertility. In the process of ART, commonly used methods for sperm separation have shortcomings and there is still room for improvement. In this study, a functional sperm selection strategy was established based on hyaluronic acid (HA) modified magnetic microbeads (MBs) and a supporting two-dimensional electromagnetic manipulation device system. Due to the modification of HA on the surface of MBs, the HA-MBs have the ability to target and bind to specific receptors on the sperm membrane to form a sperm-MB complex. A disulfide linker was introduced to connect HA and MBs. After modifying HA and connecting it with the disulfide linker, the sperm of sperm-MBs can be released under the combined effect of hyaluronidase and reduced GSH with the disulfide bond broken and HA degraded. A two-dimensional electromagnetic manipulation system was introduced to generate a magnetic field and control the directional movement of the sperm-MB complex under the guidance of an inverted microscope. The free MBs can also be removed after the sperm is released. Furthermore, the mouse sperm selected through this strategy can achieve normal insemination via ICSI and the obtained blastocysts have normal morphology and developmental milestones. This strategy has potential to be developed into an automated screening solution for the screening of functional sperm for assisted reproductive technology.

A 5-D Large-Workspace Magnetic Localization and Actuation System Based on an Eye-in-Hand Magnetic Sensor Array and Mobile Coils

Simultaneous magnetic localization and actuation in a human-scale workspace are challenging but essential for medical applications such as whole gastrointestinal (GI) tract monitoring and blood clot clearance in the leg. In this article, we propose a 5-D magnetic localization and actuation system that can track and actuate magnetic robots in a cylindrical workspace with a diameter of 500 mm. Based on the eye-in-hand configuration of the sensor array and the flexibility of the mobile electromagnetic manipulation system (mEMS), we realize a high localization accuracy in a large workspace with only 25 sensors. Moreover, we design an accurate magnetic field modeling method that can attenuate the electromagnets’ hysteresis and provide a precise actuation field estimation. Taking advantage of the mobile sensor array, we developed a signal-quality-based tracking strategy (STS) that could improve the localization performance by adjusting the movement of the sensor array. The effectiveness and advantages of the proposed methods are verified by simulations and experiments. Results show that the STS could decrease 25% position root-mean-square error (RMSE). The resulting position RMSE and orientation RMSE are 2.02 mm and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm {8.24}}^{\circ} $ </tex-math></inline-formula> , respectively. We experimentally prove the viability of the proposed strategy by propelling a magnetic helical robot through a 400-mm long 3-D twisted silicone phantom.

Electromagnetic Manipulation System for Semi-Autonomous Control of Small-Scale Magnetic Objects With Sequential Programming

In this study, an electromagnetic coil system was developed for semi-autonomous manipulation of microrobots in three-dimensional (3D) space with sequential programming. Cylindrical-shaped cores were used for the electromagnetic coils; the coils were arranged in a hemispherical configuration to allow open access to the workspace for imaging tools. The system consisted of four main parts: the electromagnetic coils, an electronic control unit, optical cameras, and a direct-manipulation graphical user interface (GUI). The system was capable of producing a magnetic field of up to 18 mT with a maximum current of 8 A current. Using this system, magnetic force and torque can be applied for semi-autonomous manipulation of magnetic objects, with different time intervals, by instantly inputting the required fields and gradients via the GUI. Sequential programming of the magnetic field allowed for better controllability and enhanced the repeatability of the system. The versatility of the system was demonstrated by moving a magnetic guidewire, micromagnet, and nanoparticles to their intended targets to assess the potential application of the system in biomedical fields.

Optimized Dynamic Motion Performance for a 5-DoF Electromagnetic Manipulation

High precision manipulation and optimization of actuation current are major concerns in the design of magnetic manipulation systems. In this paper, a flexible magnetic field mapping model has been employed to determine the field distribution of a compact electromagnetic manipulation system in 3D space, and validated by a high-resolution magnetic calibration system and Finite Element Analysis, which enables an improved accuracy and performance of magnetic manipulation. In addition, an iterative current optimization scheme is used to optimize the actuation current through Iterated Tikhonov Regularization. Finally, a feedback control algorithm including a Proportional-Integral-Derivative controller and Extended State Observer is conducted to solve general external disturbance during the autonomous manipulation of magnetic objects. By incorporating magnetic field mapping, feedback control, and current optimization model, the accuracy of the system has been demonstrated by navigating a small-size permanent magnet through predefined trajectories (Z-shaped, spiral curve) with the average position error of 0.27 mm (body length of 1 mm) and maximum average velocity of 3.59 mm/s. Meanwhile, the results showed that the required maximum actuation current was reduced from 4.00 A to 1.81 A. Our work provides a reliable and systematic approach for high-precision magnetic manipulation and optimization of actuation currents.

3D Navigation Control of Untethered Magnetic Microrobot in Centimeter-Scale Workspace Based on Field-of-View Tracking Scheme

Automatic 3D navigation control of microrobot in large microenvironment is one of the primary challenges hindering its applications. In this article, we present a systematic approach to use an electromagnetic manipulation system to deal with this challenge. Two movable orthogonal microscopic cameras scan the microenvironment on the top view and side view to build a stereo occupancy map automatically. The initial position of microrobot can be located on the basis of the similarity curves generated by the scanning sequences. In accordance with the distribution characteristic of electromagnetic fields in workspace, an enhanced rapidly exploring random tree algorithm is proposed to avoid obstacles in the complex environment. To ensure continuous visual servo in wide range, a field-of-view tracking method is developed using a specific image definition evaluation algorithm. A prescribed performance controller with disturbance observer is designed, which guarantees that the microrobot can remain in the view of microscopic cameras, and the transient and steady-state performance of the system can satisfy the expected requirements. A set of experiments are performed to verify the effectiveness of the proposed automatic 3D navigation strategy. Experimental results show that the microrobot can navigate automatically in a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{12}\,\times 10\,\times \text{10-mm}$</tex-math></inline-formula> microenvironment containing obstacles, and achieve reliable field-of-view tracking and path following at high speed.

Multi-Link Magnet Device with Electromagnetic Manipulation System for Assisting Finger Movements with Wireless Operation

We introduce a new mechanism and control system for wireless assistive finger training. The proposed mechanism and control system can provide natural finger flexion and extension via magnetic force and torque between a driving coil and a multi-link magnetic assist device placed on the fingers. The proposed mechanism is designed to allow normal movement while maintaining a natural finger shape, even when multiple magnets are applied to the fingers. Anatomical features were considered in the design to accommodate the angular changes between the fingers during hand extension and flexion. The magnetic force between the control system and the device on the hand allows extension and flexion of the fingers without the use of wires and electrical motors. The performance of the driving system and the magnetic device were verified through various simulations and experiments. A control program with motion tracking is also developed using LabView software. Hence, a wireless assistive finger training system is successfully realized.

Guide-Wired Helical Microrobot for Percutaneous Revascularization in Chronic Total Occlusion in-Vivo Validation.

For the revascularization in small vessels such as coronary arteries, we present a guide-wired helical microrobot mimicking the corkscrew motion for mechanical atherectomy that enables autonomous therapeutics and minimizing the radiation exposure to clinicians. The microrobot is fabricated with a spherical joint and a guidewire. A previously developed external electromagnetic manipulation system capable of high power and frequency is incorporated and an autonomous guidance motion control including driving and steering is implemented in the prototype. We tested the validity of our approach in animal experiments under clinical settings. For the in vivo test, artificial thrombus was fabricated and placed in a small vessel and atherectomy procedures were conducted. The devised approach enables us to navigate the helical robot to the target area and successfully unclog the thrombosis in rat models in vivo. This technology overcomes several limitations associated with a small vessel environment and promises to advance medical microrobotics for real clinical applications while achieving intact operation and minimizing radiation exposures to clinicians. Advanced microrobot based on multi-discipline technology could be validated in vivo for the first time and that may foster the microrobot application at clinical sites.

Electromagnetic Actuation of Microrobots in a Simulated Vascular Structure With a Position Estimator Based Motion Controller

The use of microrobots to achieve micromanipulation in vivo has attracted considerable attention in recent years to meet the request of non-invasiveness, precision and high efficiency in medical treatment. This letter reports the use of a home-designed electromagnetic manipulation system to control the movements of microrobots in a simulated vascular structure. After dynamic modeling, the moving trajectory of the microrobot is designed on the basis of an artificial potential field. Estimator for position is then designed with stability analysis by a Lyapunov approach. A super-twisting algorithm is further applied to control the microrobot to move along with the desired trajectory. Simulations and experiments are finally performed to demonstrate the effectiveness of the proposed control approach.

Closed-Loop Control for Trajectory Tracking of a Microparticle Based on Input-to-State Stability Through an Electromagnetic Manipulation System

Magnetic force-based manipulation has several advantages, including its minimally invasive feature and insensitivity to biological substances. Consequently, it has exhibited considerable potential in many medical applications, such as targeted delivery in precise medicine, in which microparticles are driven to the desired regions precisely in vivo. This study investigates an automated and accurate delivery of magnetic microparticles using a self-constructed electromagnetic coil system. After establishing a simplified second-order dynamic model of microparticles suspended in a fluidic environment, a visual-based automated controller that incorporates the concept of input-to-state stability (ISS) into fault-tolerant technique is developed. This controller enables microparticles to follow a desired trajectory under model uncertainties and environmental disturbances, and address the problem that the actual magnetic driving force may not reach the required value due to magnetic loss in the coil system simultaneously. Input constraint of the magnetic force provided by the system due to device capability is also considered in the fault-tolerant ISS-based controller design. Simulation and experimental results are presented to demonstrate the effectiveness of the proposed approach.

Automated In Vivo Navigation of Magnetic-Driven Microrobots Using OCT Imaging Feedback.

The application of in vivo microrobot navigation has received considerable attention from the field of precision therapy, which uses microrobots in living organisms. This study investigates the navigation of microrobots in vivo using optical coherence tomography (OCT) imaging feedback. The electromagnetic gradient field generated by a home-made electromagnetic manipulation system is magnetically modeled. With this model, the magnetic force acting on the microrobot is calculated, and the relationship between this force and the velocity of the microrobot is characterized. Results are verified through in vitro experiments wherein microrobots are driven in three types of fluid, namely, normal saline, gastric juice, and mouse urine. In vivo experiments are performed to navigate the microrobot in a mouse portal vein in which the OCT imaging system tracks the microrobot in vivo. Experimental results demonstrate the effectiveness of the proposed approach. The microrobots can be magnetically driven in the in vivo environment using the OCT imaging feedback. The significance of this study lies in providing a new method of driving microrobots in vivo.

Design and development of an electro magnetic manipulation system to actuate bioengineered magnetic micro/nanoparticles

This study introduces a new design of electromagnetic manipulation (EMM) system for wireless control of magnetic robots and magnetic nanoparticles for biomedical applications. It can generate a high-gradient magnetic field in the desired direction and forms the ponderomotive force distribution which allows the motion of magnetic robots in the specified direction. The real time microscopic-video supported by the LabVIEW vision system, the detection of object function through NI-Vision Assistant and tracking function through Math-Script node in the LabVIEW simulation. The motion speed and direction of the magnetic robotics/nanoscale material can also be manipulated using EMM system and Joystick controller.

Development of an Enhanced Electromagnetic Actuation System With Enlarged Workspace

Electromagnetic actuation is an emerging wireless control approach for manipulating magnetic microparticles for diverse minimally invasive therapy and diagnosis. This paper presents an enhanced electromagnetic manipulation system with an enlarged workspace, which is achieved by both the parametric design and the quantitative modeling of generated magnetic field of the system. The parametric design aims to characterize the influence of electromagnet parameters, such as position, radius, and height of cores on the generated electromagnetic field, so that the electromagnet specifications of the developed system can achieve a large workspace, while possessing the desired magnetic field flux density (MFFD) and gradient. With this design, the workspace of the developed prototype can reach a spherical volume with a diameter of 110 mm, the MFFD can reach 100 mT, and the gradient of MFFD can reach 2.5 T/m. The spatial distribution of electromagnetic field is quantitatively modeled using the finite-element method. Based on this model, a unit electromagnetic field distribution database for a 3-D grid of points is established. Such database enables the effective manipulation of microparticles in a considerably large workspace rather than only small central area. Experiments of manipulating paramagnetic microparticles in both 2-D and 3-D scenarios are performed to demonstrate the effectiveness of the designed system.

Real-Time Holographic Tracking and Control of Microrobots

Digital holography is used to track the three-dimensional position of a magnetic microrobot maneuvered in real time by means of an electromagnetic manipulation system. The method presented is able to process holograms at 40 Hz with a position accuracy in the imaging plane and in depth of $\pm$ 23 and $\pm$ 180 $\mu$ m, respectively. As this method does not require magnification, microrobots can be tracked in significantly larger working volumes than conventional optical methods. The performance of this tracking method is demonstrated by visually servoing a magnetic bead around a cubic trajectory.

Automatic Path Tracking and Target Manipulation of a Magnetic Microrobot.

Recently, wireless controlled microrobots have been studied because of their great development prospects in the biomedical field. Electromagnetic microrobots have the advantages of control agility and good precision, and thus, have received much attention. Most of the control methods for controlling a magnetic microrobot use manual operation. Compared to the manual method, the automatic method will increase the accuracy and stability of locomotion and manipulation of microrobots. In this paper, we propose an electromagnetic manipulation system for automatically controlling the locomotion and manipulation of microrobots. The microrobot can be automatically controlled to track various paths by using visual feedback with an expert control algorithm. A positioning accuracy test determined that the position error ranges from 92 to 293 μm, which is less than the body size (600 μm) of the microrobot. The velocity of the microrobot is nearly proportional to the applied current in the coils, and can reach 5 mm/s. As a micromanipulation tool, the microrobot is used to manipulate microspheres and microgears with the automatic control method. The results verify that the microrobot can drag, place, and drive the microstructures automatically with high precision. The microrobot is expected to be a delicate micromachine that could play its role in microfluidics and blood vessels, where conventional instruments are hard to reach.