New materials offer potential to unlock weightless technology

Researchers at Okinawa Institute of Science and Technology University (OIST)’s Quantum Mechanical Unit are studying suspended solids, which are substances that can remain suspended in a stable position without physical contact or mechanical support.

The most common type of levitation is caused by magnetic fields. By suspending objects such as superconductors and diamagnetic materials (substances that are repelled by magnetic fields) above magnets, we can develop advanced sensors that can be used in a variety of scientific and everyday applications.

Unit Director Professor Jason Twamley and a team of OIST researchers and international collaborators designed a platform that floats in a vacuum using graphite and magnets. Notably, this levitated platform operates without relying on an external power source, helping to develop ultra-sensitive sensors that provide highly accurate and efficient measurements.Their results were published in the journal applied physics letters.

When an external magnetic field is applied to “diamagnetic” materials, these materials generate a magnetic field in the opposite direction, resulting in a repulsive force that pulls them away from the magnetic field. Therefore, objects made of diamagnetic materials can float above strong magnetic fields. For example, in maglev trains, powerful superconducting magnets generate strong magnetic fields in diamagnetic materials, allowing them to levitate as if against gravity.

Graphite, the crystalline form of carbon found in pencils, is strongly repelled by magnets (highly diamagnetic). By chemically coating a powder of microscopic graphite beads with silica and mixing the coated powder with wax, researchers created thin, centimeter-sized squares that float above magnets arranged in a grid. A board was formed.

There are several challenges to creating a floating platform that does not require external power. The biggest limiting factor is “vortex damping.” This occurs when a vibrating system loses energy over time due to external forces. When an electrical conductor like graphite is passed through a strong magnetic field, there is a loss of energy due to the flow of current. This energy loss has hindered the use of magnetic levitation to develop advanced sensors.

Scientists at OIST set out to design a platform that could float and vibrate without losing energy. This means that once it starts moving, it will continue to vibrate for a long time without any additional energy input. This type of “frictionless” platform could have many applications, including new types of sensors for measuring force, acceleration, and gravity.

However, even if scientists are successful in reducing vortex damping, there is another challenge: minimizing the kinetic energy of the vibrating platform. Reducing this energy level is important for two reasons. First, it increases the sensitivity of the platform used as a sensor.

Second, cooling the movement into the quantum regime (where quantum effects dominate) could open new possibilities for precision measurements. Therefore, both vortex damping and kinetic energy challenges need to be addressed to achieve a truly frictionless, self-sustaining floating platform.

To address these, researchers focused on creating new materials derived from graphite. Through chemical changes, graphite was turned into an electrical insulator. This change stops the loss of energy while allowing the material to float in a vacuum.

Scientists continuously monitored the movement of the platform with experimental equipment. Using this real-time information, we applied a feedback magnetic force to weaken the platform’s motion, essentially cooling it and significantly slowing it down.

“Heat causes movement, but this movement can be reduced by continuously monitoring the system and providing real-time feedback in the form of corrective actions. We adjust the rate at which it is lost. By controlling the damping, we reduce the kinetic energy of the system and cool it effectively,” Professor Twamley explained.

“If sufficiently cooled, our levitated platforms have the potential to outperform even the most sensitive atomic gravimeters ever developed. Achieving this level of accuracy requires rigorous engineering to isolate the platform from external disturbances such as vibrations, magnetic fields, and electrical noise. not. Our ongoing efforts are focused on refining these systems to unlock the full potential of this technology. ”

Professor Twamley’s unit focuses on using floating materials to build mechanical oscillators, systems that move repetitively or periodically around a central point. These vibrations occur in a variety of situations, including pendulums, masses connected to springs, and sound systems.

This research opens up exciting possibilities for ultrasensitive sensors to enable precise control of vibration platforms. By combining levitation, insulation and real-time feedback, Professor Twamley’s team is pushing the boundaries of what can be achieved with materials science and sensor technology.