# A*STAR levitated magnet microrotor reaches 138 million rpm at 4.2 K in lab tests

- Published: 2026-11-07 16:43 UTC
- Section: Science › Instruments & experiments
- Tags: levitated microrotor, 138 million rpm, Meissner effect, superconducting lead trap, cryogenic pressure sensing, thermal torque noise, axion-like dark matter, neodymium magnet, A*STAR Singapore, Science Advances
- URL: https://realtech.media/news/rt-5667e10ea57cd647f4428d32_a_star_levitated/

**Researchers at Singapore's A*STAR spun a levitated magnetic microsphere to 138 million rpm; the lab setup also measured gas pressure at cryogenic temperature.**

![A*STAR levitated magnet microrotor reaches 138 million rpm at 4.2 K in lab tests](https://realtech.media/media/2026/11/84b15b82c3640e90.webp)
*scinexx*

Researchers at the Agency for Science, Technology and Research (A*STAR) in Singapore, led by Dr. Tao Wang, spun a magnetic microsphere levitated by the Meissner effect to above 2.3 megahertz, or 138 million rpm. The result is reported in Science Advances [1]. The experiment ran at 4.2 kelvin. According to the study, the previous best value for a magnetically levitated rotor was 660,000 rotations per second [1].

The authors report an exceptionally low damping rate of 4.75 × 10⁻⁷ hertz under the most favourable vacuum conditions [1]. By the measured model, the rotation speed would fall to half only after about 17 days without drive.

## Superconducting trap and rotor

The magnets were nearly spherical and made of a neodymium-iron-boron alloy. Their radii were between about 24 and 30 micrometers, which corresponds to diameters of roughly 48 to 60 micrometers. The 138 million rpm figure was reached with a magnet of about 30 micrometers radius.

The rotor levitated in a superconducting lead trap inside a vacuum chamber cooled with liquid helium to 4.2 kelvin, about minus 269 degrees Celsius. A magnetic coil set the sphere spinning, and a superconducting quantum interference device (SQUID) recorded its motion. According to the study, higher speeds are conceivable with faster readout electronics but are ultimately limited by the mechanical stress on the sphere.

## Pressure sensing and a first dark matter search

Residual gas molecules slow the rotor, and at very low pressure this friction is approximately proportional to gas density. The team therefore determined pressure from the decay of rotation speed directly at the cold measurement position [1]. Measurements were demonstrated over a range of about 10⁻³ to 10⁻⁸ millibar. At the lowest pressures the value was inferred from rotational damping and was not confirmed by a second, independent gauge at the rotor. The method remains a laboratory experiment, not a production-ready sensor.

The rotating magnet can also be synchronized to an external periodic magnetic field. In this mode the setup detected thermal torque noise at 20 kilohertz [1]. The data were used for a first, narrowly limited search for axion-like dark matter, which in some models would appear as an extremely weak alternating magnetic field.

No suitable signal was found in the examined frequency window of about two hertz, so only an upper limit on the possible interaction could be derived. The authors describe the result as preliminary; it is not evidence of dark matter. Measurements over a much wider frequency range and with further reduced interference would be needed to show how capable the rotor is as an instrument.

## Sources

1. [Science Advances](https://doi.org/10.1126/sciadv.aee6434)
2. [scinexx](https://www.scinexx.de/news/physik/rekord-schwebender-magnet-rotiert-138-millionen-mal-pro-minute)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-5667e10ea57cd647f4428d32_a_star_levitated/