Magnetic nanoparticles (MNPs) have been widely used as effective agents for actuation and localization for targeted drug delivery (TDD). Especially for the localization of MNPs, magnetic particle imaging (MPI) has been developed to use magnetization generated by a magnetic field for imaging. However, most MPI systems use a bore-type structure, and there exist limitations in terms of working space, compatibility with surrounding medical devices, and responding to emergency situations from a medical perspective. To address these issues, we propose a novel open-structure magnetic particle spectroscopy (OMPS) technique. The structural design, theoretical background, and analysis of the proposed OMPS are presented, and experiments were conducted to evaluate the proposed OMPS. The experimental results indicate that the detection volume can be obtained as a cylindrical region of interest (ROI) of 50 50 25 mm, and the feasibility can be exhibited within the same or larger ROI with similar amounts of Resovist as used in previous MPI studies. The results could demonstrate the promising potential for open-structure MPS.

Active drug delivery systems for cancer therapy are gaining attention for their biocompatibility and enhanced efficacy compared to conventional chemotherapy and surgery. To improve precision in targeted drug delivery (TDD), actuating devices using external magnetic fields are employed. However, a key challenge is the inability to visually track magnetic drug carriers in blood vessels, complicating navigation to the target. Magnetic particle imaging (MPI) systems can localize magnetic carriers (MCs) but rely on bulky electromagnetic coils to generate a static magnetic field gradient, creating a field-free point (FFP) within the field of view (FOV). Also, additional coils are required to move the FFP across the FOV, limiting flexibility and increasing the system size. To address these issues, we propose a non-FFP-based, open-type RF coil system with a simplified structure composed of a Tx/Rx coil and a permanent magnet at the coil center, eliminating the need for an FFP. Furthermore, integrating a robotic arm for coil assembly enables easy adjustment of the FOV size and location. Finally, imaging tests with magnetic nanoparticles (MNPs) confirmed the system’s ability to detect and localize a minimum mass of 0.3 mg (Fe) in 80 × 80 mm².

This study introduces a tunable acoustic tweezer system designed for precise three-dimensional particle trapping and manipulation. The system utilizes a dual-liquid-layer acoustic lens, which enables the dynamic control of the focal length through the adjustable curvature of a latex membrane. This tunability is essential for generating the acoustic forces necessary for effective manipulation of particles, particularly along the direction of acoustic wave propagation ($z$-axis). Experiments conducted with spherical particles as small as 1.5 mm in diameter demonstrated the system’s capability for stable trapping and manipulation. Performance was rigorously evaluated through both $z$-axis and 3D manipulation tests. In the z-axis experiments, the system achieved a manipulation range of 33.4–53.4 mm, with a root-mean-square error and standard deviation of 0.044 ± 0.045 mm, which highlights its precision. Further, the 3D manipulation experiments showed that particles could be accurately guided along complex paths, including multilayer rectangular and helical trajectories, with minimal deviation. A visual feedback-based particle navigation system significantly enhanced positional accuracy, reducing errors relative to open-loop control. These results confirm that the tunable acoustic tweezer system is a robust tool for applications requiring precise control of particles with diameter of 1.5 mm in three-dimensional environments. Considering its ability to dynamically adjust the focal point and maintain stable trapping, this system is well suited for tasks demanding high precision, such as targeted particle delivery and other applications involving advanced material manipulation.