Advances in technology have led to the miniaturization of many mechanical, electronic, chemical and biomedical products, and with that, an evolution in the way these tiny components and parts are transported is necessary to follow. Transport systems, such as those based on conveyor belts, suffer from the challenge of friction, which drastically slows the speed and precision of small transport. Researchers from YOKOHAMA National University addressed this issue by developing an untethered levitation device capable of moving in all directions. The frictionless design allows for ultrafast, agile movement that can prove to be very valuable in machine assembly, biomedical and chemical applications via contactless transport.
Researchers published their results in Advanced Intelligent Systems in July 2025.
The experimental results of the study aligned with the theoretical results researchers had hoped for, proving the levitation device has thwarted friction successfully. The device maintained frictionless movement for over three meters per second on an inclined surface. At an incline of 10°, the device moved freely when levitation was turned on, and when levitation was off, the device could not move past the force of gravity, proving the effectiveness of the levitation component.
Additionally, researchers tested the device while carrying weight, as this will be a vital part of its intended function when used in practice. The device continues to levitate and move freely when under 150 grams total, allowing for about 43 grams of weight to be added to the device. However, more weight than this results in no levitation or movement.
The development of this free-moving, ultrafast device could have been done using diamagnetic levitation or pneumatic levitation; however, those options had limitations (magnetic and pressurized gas generators, respectively) that would not align with the research goal of realizing the cm-sized levitation device without reliance of the outer device. Instead, acoustic levitation was used, which utilizes sound waves to suspend objects in the air. Acoustic levitation is not without its own issue: cables.
"While acoustic levitation removes floor friction, conventional systems rely on cables that disturb positioning. We solved this by developing an untethered levitation device with a wireless drive circuit, enabling stable levitation height and high-speed, flexible transport," said Ohmi Fuchiwaki, author of the study, associate professor and researcher at YOKOHAMA National University.
Along with acoustic levitation and the cable work-around, a piezoelectric actuator, which is a device that converts electrical energy into mechanical force, was used to generate a squeeze film, a term to describe the behavior of a thin film of fluid squeezed between two surfaces, to yield the omnidirectional, frictionless transport device free from cables or other tethers.
The future of this device involves continued improvement in the levitation efficiency as well as enhancing its stability under a load and on irregular surfaces. Down the line, researchers look towards developing a robot by using multiple levitation devices and a propulsion mechanism to make more practical use of this technology for the contactless delivery of machine parts, biomedical cells and other small components.
Yuta Sunohara, Soushi Ueno, Rintaro Minegishi, Chihiro Sekine, Yuta Kitamura, Yuna Sugiyama, Satoshi Andoand Ohmi Fuchiwaki of the Department of Mechanical Engineering at YOKOHAMA National Univeristy, and Akihiro Torii of the Department of Electrical Engineering at Aichi Institute of Technology contributed to this research.
The Nakanishi Scholarship Foundation, the NSK Foundation for the Advancement of Mechatronics and the Takahashi Industrial and Economic Research Foundation supported this research.
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YOKOHAMA National University (YNU) is a leading research university dedicated to academic excellence and global collaboration. Its faculties and research institutes lead efforts in pioneering new academic fields, advancing research in artificial intelligence, robotics, quantum information, semiconductor innovation, energy, biotechnology, ecosystems, and smart city development. Through interdisciplinary research and international partnerships, YNU drives innovation and contributes to global societal advancement.
