A research group led by Associate Professor Atsushi Sakurai of the Faculty of Engineering has developed a "metamaterial radiator" that dissipates heat efficiently even at extremely low temperatures.
A research group led by Associate Professor Atsushi Sakurai of the Department of Mechanical Systems Engineering, Faculty of Engineering, our university, Principal Researcher Junko Tachikawa of the Japan Aerospace Exploration Agency (JAXA), and Professor Tomohiko Saito of the Department of Applied Physics, Faculty of Advanced Engineering, Tokyo University of Science, has successfully developed a new type of "metamaterial radiator" (Note 1) (Note 2) that can maintain high radiative performance even in extremely low temperature environments. This research result was published on October 21, 2025, in "Applied Thermal Engineering (Elsevier)," a leading international journal in the field of thermal engineering.
Key points of this research
- We have developed a metamaterial radiator with high emissivity (Note 3) in the ultra-low temperature far-infrared region (50–150 µm).
- Design optimization based on the equivalent LC model (Note 4) and the FDTD method (Note 5), and verification through prototyping and spectroscopic measurements.
- The study confirmed that the emissivity of the new paint surpassed that of conventional black paint (Z306) at 50–100 K, providing a new guideline for the thermal design of spacecraft.
[Terminology]
(Note 1) Metamaterial:
This new material artificially creates structures that do not exist in nature on a nano- to micrometer scale, allowing for the precise control of electromagnetic waves such as light and heat. By periodically arranging metals and dielectrics, absorption and reflection characteristics can be arbitrarily designed within specific wavelength ranges.
(Note 2) Radiator:
A structure that releases heat to the outside as electromagnetic waves (infrared radiation). In environments where heat conduction and convection are difficult, such as outer space, radiators are the only means of heat dissipation. In this research, we developed a "metamaterial radiator" that can emit infrared radiation with high efficiency even at extremely low temperatures.
(Note 3) Emissivity:
Emissivity is a value that indicates how efficiently an object can emit heat as infrared radiation. The emissivity of a perfect radiator (an ideal black body) is set to 1, and the emissivity of actual materials is expressed in the range of 0 to 1. A higher value indicates more efficient heat release into space. The metamaterial radiator developed in this study showed a higher emissivity than conventional black paint (Z306).
(Note 4) Equivalent LC Circuit Model:
This method approximates microstructures composed of metals and dielectrics as a combination of inductance (L) and capacitance (C) in an electrical circuit, and theoretically analyzes the characteristics of electromagnetic resonance. By changing the dimensions of the structure and the thickness of the layers, the radiation characteristics can be precisely controlled.
(Note 5) FDTD method (Finite-Difference Time-Domain Method):
This method analyzes the behavior of electromagnetic waves by discretizing time and space and numerically solving Maxwell's equations. It can accurately calculate the distribution of light and infrared reflection, transmission, and absorption in complex nanostructures.
Research details
Paper information
[Publication] Applied Thermal Engineering (Elsevier)
[Paper Title] Design and Characterization of Cryogenic Metamaterial Radiators for Spacecraft Applications
[Authors] Masashi Higashiura, Sumitaka Tachikawa, Tomohiko Saitoh, Atsushi Sakurai
[doi]10.1016/j.applthermaleng.2025.128743