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.

Objective: 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. Methods: 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. Results: The devised approach enables us to navigate the helical robot to the target area and successfully unclog the thrombosis in rat models in vivo. Conclusion: 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. Significance: 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.

In this paper, we present a tattooing capsule endoscope (TCE) that can localize an intestinal lesion or tumor for a preoperative laparoscopic surgery. The TCE is based on a wireless capsule endoscope (WCE) structure and can be actively controlled by an external electromagnetic actuation system to move, observe, and mark the target lesion in the gastrointestinal (GI) tract. The TCE is designed to perform capsule locomotion, needle extrusion and intrusion motions, and ink injection. First, the TCE is controlled to move to the target lesion during GI tract diagnosis via a capsule endoscopic camera. Further, a tattooing needle is extruded by an electromagnetically controlled mechanism to puncture the tissue. Finally, the tattooing ink is injected by the chemically reacted carbon dioxide gas pressure that is triggered by a shape memory alloy wire and a reed switch. The reed switch is also activated by the external magnetic field flux density. The suggested methods were verified by the ex-vivo experiments. The TCE prototype was able to move to the target lesion and inject the ink beneath the mucosa layer safely, thereby leaving a visible tattooed mark for surgical lesion identification. The proposed TCE method can accelerate the development of functionalities as well as tattooing procedures of the WCE in the GI tract.

Untethered small-scale soft robots have been widely researched because they can be employed to perform wireless procedures via natural orifices in the human body, or other minimally invasive operations. Nevertheless, achieving untethered robotic motion remains challenging owing to the lack of an effective wireless actuation mechanism. To overcome this limitation, we propose a magnetically actuated walking soft robot based on paper and a chained magnetic-microparticle-embedded polymer actuator. The magnetic polymer actuator was prepared by combining Fe₃O₄ magnetic particles (MPs, diameter of ~50 nm) and silicon that are affected by a magnetic field; thereafter, the magnetic properties were quantified to achieve proper force and optimized according to the mass ratio, viscosity, and rotational speed of a spin coater. The fabricated polymer was utilized as a soft robot actuator that can be controlled using an external magnetic field, and paper was employed to construct the robot body with legs to achieve walking motion. To confirm the feasibility of the designed robot, the operating capability of the robot was analyzed through finite element simulation, and a walking experiment was conducted using electromagnetic actuation. The soft robot could be moved by varying the magnetic flux density and on–off state, and it demonstrated a maximum moving speed of 0.77 mm/s. Further studies on the proposed soft walking robot may advance the development of small-scale robots with diagnostic and therapeutic functionalities for application in biomedical fields.