Optimized Halbach array for focused magnetic drug targeting

Magnetic drug targeting (MDT) is a therapeutic method that delivers drug carriers containing magnetic nanoparticles to a target lesion by directing them using an external magnetic field. To minimize the possible side effects on the surrounding normal cells, focused magnetic drug targeting (FMDT) has been introduced, which allows drug carriers to be delivered only to the target lesions. FMDT, with its capability for local focusing and wide attraction, aims for highly efficient and concentrated drug delivery. In this study, a modified quasi-axisymmetric Halbach array design was introduced as an external magnetic source to perform FMDT. The proposed Halbach array design has a simple structure that is easy to assemble, unlike earlier Halbach array designs. The optimized Halbach array is fabricated as a result of the optimization of the magnetic force magnitude and local focusing with wide attraction using finite element method (FEM) analysis. Through simulations and experiments, the optimized Halbach array design is validated and a comparative analysis with other magnet types is performed. As a result, the optimization of the Halbach array using FEM is experimentally validated, and it is confirmed that the optimized Halbach array is more effective for FMDT than the permanent magnet used in MDT. © 2020 Elsevier B.V.1

Analysis of drivable area and magnetic force in quadrupole electromagnetic actuation system with movable cores

Recently, significant attention has been paid to the development of electromagnetically actuated microrobots. Various types of electromagnetic actuation (EMA) systems have been proposed and put into practice. Owing to their limited workspace and driving force, the previous EMA systems were used restrictively in microrobots of specific sizes. Arguably, more research should be conducted on driving microrobots of various sizes using a single EMA system. In this study, a novel quadrupole EMA system with movable magnetic cores is proposed for driving microrobots of various sizes. Sharp magnetic cores and a closed magnetic circuit method are introduced to generate a magnetic field of high intensity and gradient with a small current. In addition, an analytical definition of the drivable area (DA) is presented in which a microrobot can move to the desired direction. The DA is estimated using a finite element method (FEM) and is verified via experimental results. The effectiveness of the proposed EMA system is verified by analyzing the changes in DA and magnetic force according to variations in the positions of the magnetic core. The results imply that driving microrobots of various sizes is possible. Moreover, it is shown that an EMA system with movable cores could be manipulated more efficiently than those with fixed cores. © 2020 Elsevier Ltd1

Magnetically steerable manipulator with variable stiffness using graphene polylactic acid for minimally invasive surgery

For manipulators used in minimally invasive surgery (MIS), variable stiffness and miniaturization are very important characteristics. However, previously proposed mechanisms are difficult to miniaturize due to large and complex structures; thus, they do not achieve variable stiffness characteristics, consequently being difficult to be applied to manipulators used in MIS. In this study, we proposed a manipulator that can be magnetically steered by a permanent magnet at the end and can have variable stiffness characteristics by a phase transition of graphene polylactic acid (GPLA). Thus, the proposed manipulator is easy to fabricate and miniaturize as a magnetic steering MIS manipulator. To verify the magnetic steering and variable stiffness performances of the proposed manipulator, various basic experiments and analysis simulations were executed. In addition, by applying the discriminating properties of the proposed manipulator (magnetic steering, variable stiffness), we can construct a double-segment manipulator with variable stiffness and verify its implementation in postures which are difficult to achieve in other MIS manipulators. © 2020 Elsevier B.V.1

pH Sensor-Embedded Magnetically Driven Capsule for H. pylori Infection Diagnosis

The Campylobacter-like organism (CLO) test is the most commonly employed test for diagnosing Helicobacter pylori (H. pylori) infection in the stomach. Since the CLO test is an invasive method, non-invasive methods have been proposed. However, the proposed methods exhibit relatively low specificity and sensitivity. In this letter, a novel H. pylori infection diagnosis method that uses a pH sensor-embedded magnetically driven capsule is proposed. The proposed method adopts the principle of the CLO test to diagnose H. pylori infection non-invasively. The capsule comprises two chambers to sample gastric juice, and a pH sensor is embedded inside each chamber. Therefore, H. pylori infection can be diagnosed using the urea hydrolysis property of H. pylori and a pH sensor embedded in the chambers of the capsule. In addition, the capsule can be magnetically actuated using an external magnetic field owing to its neodymium-magnet. The performance of the proposed capsule was evaluated in several aspects. First, the sensing ability of the fabricated pH sensor was verified using a pH buffer solution. Second, the magnetic actuation capacity of the capsule was evaluated using a 6-coil electromagnetic actuation (EMA) system. Third, the gastric juice sampling and pH-sensing capabilities of the assembled capsule were evaluated using a phantom test. Finally, the ability to diagnose H. pylori infection was validated using an ex vivo test. Consequently, this letter highlights the potential feasibility of establishing an H. pylori infection diagnosis method using a pH sensor-embedded magnetically driven capsule

Reprogrammable Magnetically Actuated Self‐Assembled Cilia Array

Motile cilia move in an asymmetric pattern and implement a metachronal wave (MCW) to facilitate fluid movement in a viscous environment. Studies have been conducted to mimic MCW movement of motile cilia, but the fabrication process is too complicating or there are difficulties in accurately mimicking the shape of the cilia. To overcome these limitations, a self‐assembly method is introduced to fabricate a reprogrammable magnetically actuated self‐assembled (RMS) cilia array that can be reprogrammed by changing the magnetization direction through additional magnetization. Using the RMS cilia array, a unilateral cilia array (UCA) channel and a bilateral cilia array (BCA) channel are constructed, and the motion and fluid flow of the RMS cilia array are analyzed by applying different magnetic fields (strike magnetic field and rotating magnetic field). When a rotating magnetic field is applied to the UCA channel, a distinct MCW appears. In the BCA channel test, fluid pumping is observed when a strike magnetic field is applied, whereas fluid mixing is observed when a rotating magnetic field is applied. Based on these results, it is expected that the proposed RMS cilia array and magnetic field actuation can be applied to lab‐on‐a‐chip or microfluidic channels for fluid mixing and pumping

pH Sensor-Embedded Magnetically Driven Capsule for H. pylori Infection Diagnosis

The Campylobacter-like organism (CLO) test is the most commonly employed test for diagnosing () infection in the stomach. Since the CLO test is an invasive method, minimally invasive methods have been proposed. However, the proposed methods exhibit relatively low specificity and sensitivity. In this letter, a novel infection diagnosis method that uses a pH sensor-embedded magnetically driven capsule is proposed. The proposed method adopts the principle of the CLO test to diagnose infection minimally invasively. The capsule comprises two chambers to sample gastric juice, and a pH sensor is embedded inside each chamber. Therefore, infection can be diagnosed using the urea hydrolysis property of and a pH sensor embedded in the chambers of the capsule. In addition, the capsule can be magnetically actuated using an external magnetic field owing to its neodymium-magnet. The performance of the proposed capsule was evaluated in several aspects. First, the sensing ability of the fabricated pH sensor was verified using a pH buffer solution. Second, the magnetic actuation capacity of the capsule was evaluated using a 6-coil electromagnetic actuation (EMA) system. Third, the gastric juice sampling and pH-sensing capabilities of the assembled capsule were evaluated using a phantom test. Finally, the ability to diagnose infection was validated using an ex vivo test. Consequently, this letter highlights the potential feasibility of establishing an infection diagnosis method using a pH sensor-embedded magnetically driven capsule. IEEEFALS

Registration-free Minimally Invasive Surgery Without Preoperative Phase

Many types of research on robot-assisted minimally invasive surgery (RMIS) have been conducted, and its use in actual surgery is increasing. However, prior image information regarding the surgical target is required to generate a path for the surgical tool for RMIS. The image coordinate, target’s coordinate, and robot coordinate should be aligned through registration. However, errors are bound to occur during the image acquisition and registration. As the image acquisition time and registration time increase, the error between the patient and the coordinate information at the time of the actual operation increases due to the movement of the patient. To minimize these errors, this study proposes a registration-free approach to MIS without the preoperative phase in which a robot is used to directly contact the target to obtain a point cloud and reconstruct the shape information of the target. Using the position-based impedance and constraint controls for the remote center of motion (RCM) of the robot for MIS, the position information of the target can be acquired in the form of a point cloud without damage. Further, by converting the obtained point cloud into a mesh form using the Point2Mesh deep learning algorithm, it is possible to reconstruct the area where the position information is insufficient because there is no contact among the target areas. The process could obtain the coordinates within 3 min for the phantom. After a deep learning process of about 10 min, a surgical path using a robot could be generated. The reconstruction accuracy showed a RMSE of up to 0.35 mm. Additionally, this method enables the acquisition of stiffness information of the target, unlike using the prior image information. Therefore, it is expected that a stiffness overlay can be constructed and used for the diagnosis and treatment of targets. © 2023, ICROS, KIEE and Springer.FALS

Active Multiple-Sampling Capsule for Gut Microbiome

It is well known that the gut microbiome performs necessary physiological functions for the host organism, such as preventing infection from various pathogens, promoting the immune system's maturation, participating in nutrition absorption and metabolism processes, and promoting anticancer functions. To understand the relationship between the gut microbiome and host, multiple microbial samplings and analyses from certain locations in the gastrointestinal (GI) tract are necessary. However, ingestible sampling capsules, previously designed for gut-microbiome sampling, rely on the peristaltic motion of the intestine and can perform sampling only once, when the capsule body is submerged in the gut fluid. In this article, we propose an active multiple-sampling capsule that can be actively moved (by an external magnetic field) to specific locations in the GI tract and collects multiple gut-microbe-containing intestinal fluid samples. In particular, because the proposed capsule includes three microchannels, three inlet ports, and a small permanent magnet (for alignment), it can perform selective sampling with minimal cross-contamination, by allowing the capsule to move to the target location and aligning the inlet port of one of the three microchannels downwards. Through basic performance tests, we evaluate the locomotive and microbial-sampling performances of the proposed capsule (locomotion accuracy: similar to 1.39 degrees; inlet-port alignment accuracy: similar to 1.48 degrees; maximum suction flow rate: 22.3 mu L/min); furthermore, through phantom and ex vivo tests, we verify the feasibility of the proposed capsule. We confirm that the proposed active multiple-sampling capsule can be moved to the desired target locations in the GI tract and can collect similar to 45 mu L gut-microbe-containing intestinal fluid thereat; furthermore, it can perform up to three samplings with minimal cross-contamination. In the future, we expect the proposed capsule to be implemented in medical research, to understand the gut microbiome's role in the human body (via the collection and analysis of these microbiomes) and to diagnose various human diseases.FALS

Exosome-based hybrid nanostructures for enhanced tumor targeting and hyperthermia therapy

Recently, natural exosomes have attracted attention as an ideal drug carrier to overcome the limitations of existing drug delivery systems which are toxicity induction and low cancer-targeting performance. In this study, we propose an exosome-based hybrid nanostructure (EHN) with improved targeting ability and therapeutic efficacy against colorectal cancer by using exosomes isolated from the tumor cell line as a drug carrier. The proposed EHN can have high biocompatibility by using exosomes, a biologically derived material, and show improved targeting performance by adding a tumor-targeting ligand (folic acid). In addition, the proposed EHN is capable of chemotherapy because doxorubicin, an anticancer drug, is encapsulated by the exosome with high efficiency, and it can induce hyperthermia therapy because of the magnetic nanoparticles (MNPs) attached to the surface of exosomes. Through in vitro and in vivo experiments using a xenograft tumor mouse model, it was confirmed that the proposed EHN could exhibit increased apoptosis and excellent tumor growth inhibition ability. Therefore, the proposed EHN is expected to overcome the limitations of existing drug delivery systems and be utilized as an effective drug delivery system in cancer treatment. © 2021 Elsevier B.V.1