Researchers at the Quantum Machine Unit of the Okinawa Institute of Science and Technology Graduate University (OIST) in Japan are exploring a novel material capable of maintaining a stable suspended state without any physical contact or mechanical support.
The research team has devised a suspension platform utilizing graphite and magnets within a vacuum environment. Notably, this suspension platform operates without the need for an external power source, offering potential applications in the development of ultra-sensitive sensors for achieving precise and efficient measurements. Their findings have recently been published in the journal Applied Physics Letters.
Image Source: OIST
When an external magnetic field is applied to "diamagnetic" materials, they generate a magnetic field in the opposite direction, resulting in repulsion. Thus, objects made of diamagnetic materials can float above strong magnetic fields. For instance, in magnetic levitation trains, powerful superconducting magnets create a strong magnetic field, allowing diamagnetic materials to achieve levitation, seemingly defying gravity.
Graphite, a crystalline form of carbon found in pencils, exhibits strong repulsion to magnets (strong diamagnetism). By chemically coating microscale graphite powder with silicon dioxide and mixing the coated powder with wax, researchers formed a centimeter-sized square disc that floated above a grid-patterned arrangement of magnets.
However, achieving a truly frictionless, self-sustaining levitation platform requires addressing challenges in eddy current damping and kinetic energy.
To this end, researchers are focusing on creating a new material derived from graphite. By chemically altering it, they transform graphite into an electrical insulator. This change can prevent energy loss while allowing the material to float in a vacuum.
In their experimental setup, scientists continuously monitor the platform's motion. Using this real-time information, they apply feedback magnetic forces to suppress the platform's motion—essentially cooling its movement and significantly slowing down its speed.
Professor Jason Twamley, the lead author of the paper and head of the Quantum Machine Unit at OIST, explains: "Heat causes motion, but by continuously monitoring and providing real-time feedback to the system in corrective measures, we can reduce this motion. Feedback adjusts the damping rate of the system, i.e., how quickly it loses energy, so by actively controlling damping, we can lower the system's kinetic energy, effectively cooling it down."
"If sufficiently cooled, our levitation platform could even outperform the most sensitive atomic gravimeters developed to date. These are cutting-edge instruments that precisely measure gravity using atomic behavior. Achieving this level of precision requires meticulous engineering design to isolate the platform from external disturbances such as vibrations, magnetic fields, and electrical noise. Our focus is on refining these systems to unleash the full potential of this technology."
This research opens up exciting possibilities for ultra-sensitive sensors and precise control of oscillating platforms. By combining levitation, insulation, and real-time feedback, Twamley's team is advancing the development of materials science and sensor technology.
Related paper information: https://doi.org/10.1063/5.0189219
