Toward wireless medical microrobot applications driven by an electromagnetic actuation (EMA) system, challenges associated with movability, the electromagnetic force, and the coil system size must be addressed. This paper presents an enhanced EMA system with a higher magnetic field via new coil configurations, an independent magnetic field control method, and application to the multi-degree-of-freedom (DOF) motion of an untethered capsule endoscope. The magnetically actuated capsule endoscope (MACE) system proposed herein consists of an endoscopic capsule with a permanent magnet in the body, eight air-cored stationary electromagnetic coils, and a control system. The coil system is designed to maximize the working space available within a limited equipment space. The MACE is designed to perform full 5-DOF motion, including 3-DOF translation and 2-DOF rotation. The independent magnetic field control method with the new coil configuration enables orientation-independent-driving (OID) control of the capsule endoscope that could not be accomplished by previous EMA systems. The developed system performance was verified by simulations and experiments. The MACE motion in the spatial domain was evaluated with a robotic endoscopic procedure and diagnostic performance by in-vitro and ex-vivo experiments.

Capsule endoscopes (CEs) have emerged as an advanced diagnostic technology for gastrointestinal diseases in recent decades. However, with regard to robotic motions, they require active movability and multi-functionalities for extensive, untethered, and precise clinical utilization. Herein, we present a novel wireless biopsy CE employing active five degree-of-freedom locomotion and a biopsy needle punching mechanism for the histological analysis of the intestinal tract. A medical biopsy punch is attached to a screw mechanism, which can be magnetically actuated to extrude and retract the biopsy tool, for tissue extraction. The external magnetic field from an electromagnetic actuation (EMA) system is utilized to actuate the screw mechanism and harvest biopsy tissue; therefore, the proposed system consumes no onboard energy of the CE. This design enables observation of the biopsy process through the capsule’s camera. A prototype with a diameter of 12 mm and length of 30 mm was fabricated with a medical biopsy punch having a diameter of 1.5 mm. Its performance was verified through numerical analysis, as well as in-vitro and ex-vivo experiments on porcine intestine. The CE could be moved to target lesions and obtain sufficient tissue samples for histological examination. The proposed biopsy CE mechanism utilizing punch biopsy and its wireless extraction–retraction technique can advance untethered intestinal endoscopic capsule technology at clinical sites.

In this article, we present a novel stationary electromagnetic actuation system (EMS) and a redundant magnetic field control approach that can enhance the magnetic actuation ability for a capsule endoscope. The EMS configured with multiple electromagnets has an intrinsic redundant problem when computing input current to each coil from inverse formulation. Here, we propose a redundant electromagnetic field control scheme of utilizing this redundancy to increase magnetic force and reduce the peak input current that deteriorates the performance. It is based on the optimization of magnetic field encountering input current and null-space equations of a pseudoinverse matrix. We validated the proposed methods in simulation and experiments through the prototyped EMS designed by considering actual human size and a magnetic capsule endoscope. The results show significant improvements in the magnetic field and lower input current compared to the conventional method as well as extended operating time through reduced heating effects. Especially, the in vitro in a gastric phantom and in vivo experiments in a live pig could prove the practical applicability of the developed method for a magnetic capsule endoscope toward upper stomach diagnosis in the clinical environment.

Recent research efforts regarding advanced Robotic Capsule Endoscopes (RCEs) have primarily focused on the development of actively locomotive endoscope capsules. However, accurate movement of an RCE inside the digestive organs remains a challenge that hinders the further development of an autonomous RCE that with applicability in clinical practice. To address this challenge, this study proposed and developed a novel three-dimensional (3D) location positioning method that is compatible with an RCE manipulated by an external magnetic actuation system. The developed localization methodology employed one embedded single-axis receiving coil (Rx) in the RCE and three external transmitting coils (Txs) placed under the clinical bed. The magnetic flux density obtained from the electromotive force at the Rx was applied to the solution of 3D nonlinear Biot–Savart equations and enabled the determination of the position of the Rx in relation to the corresponding magnetoquasistatic field source in the Tx. For implementation, this study developed: (1) an accurate mathematical model and volumetric analysis method for the magnetoquasistatic field by applying equipotential contour and surface mapping, (2) a method to determine the optimal Tx arrangement, and (3) a prototyped device and in-vitro validation of the feasibility of the 3D localization. In the helical trajectory tracking experiment, the device demonstrated an error of 2.03 ± 1.14 mm, and the feasibility in the clinical environment was verified through gastrointestinal phantom experiments. The proposed method will be further evaluated clinically for the retargeting and accurate localization of internal pathologies as well as the closed-loop control of an actively locomotive RCE.

This paper presents an active locomotion capsule endoscope system with 5D position sensing and real-time automated polyp detection for small-bowel and colon applications. An electromagnetic actuation system (EMA) consisting of stationary electromagnets is utilized to remotely control a magnetic capsule endoscope with multi-degree-of-freedom locomotion. For position sensing, an electronic system using a magnetic sensor array is built to track the position and orientation of the magnetic capsule during movement. The system is integrated with a deep learning model, named YOLOv3, which can automatically identify colorectal polyps in real-time with an average precision of 85%. The feasibility of the proposed method concerning active locomotion and localization is validated and demonstrated through in vitro experiments in a phantom duodenum. This study provides a high-potential solution for automatic diagnostics of the bowel and colon using an active locomotion capsule endoscope, which can be applied for a clinical site in the future.

Targeted drug delivery (TDD) based on magnetic nanoparticles (MNPs) and external magnetic actuation is a promising drug delivery technology compared to conventional treatments usually utilized in cancer therapy. However, the implementation of a TDD system at a clinical site based on considerations for the actual size of the human body requires a simplified structure capable of both external actuation and localization. To address these requirements, we propose a novel approach to localize drug carriers containing MNPs by manipulating the field-free point (FFP) mechanism in the principal magnetic field. To this end, we devise a versatile electromagnetic actuation (EMA) system for FFP generation based on four coils affixed to a movable frame. By the Biot–Savart law, the FFP can be manipulated by appropriately controlling the gradient field strength at the target area using the EMA system. Further, weighted-norm solutions are utilized to correct the positions of FFP to improve the accuracy of FFP displacement in the region of interest (ROI). As MNPs, ferrofluid is used to experiment with 2D and 3D localizations in a blocked phantom placed in the designed ROI. The resultant root mean square error of the localizations is observed to be approximately 1.4 mm in the 2D case and 1.6 mm in the 3D case. Further, the proposed movable EMA is verified to be capable of simultaneously scanning multiple points as well as the actuation and imaging of MNPs. Based on the success of the experiments in this study, further research is intended to be conducted in scale-up system development to design precise TDD systems at clinical sites.