Researchers at AIST, in collaboration with Shimane University, have succeeded in developing a unique thermoelectric material (goniopolar material) that can orthogonalize temperature differences and current direction.
Most primary energy is discharged as heat, and to make effective use of this unused heat (waste heat), development of thermoelectric materials that convert heat into electricity is underway worldwide. In recent years, new materials with high performance have been reported one after another, but only Bi₂Te₃ based materials, which were discovered more than half a century ago and operate near room temperature, have been put to practical use. The lack of practical thermoelectric modules that can operate at temperatures higher than room temperature has hindered progress in power generation using waste heat. In particular, conventional thermoelectric modules have a "longitudinal" configuration in which the heat flow and the power generation direction are the same, which causes elemental diffusion and other reactions at the electrode interface in contact with the high-temperature heat source during power generation, leading to degradation, which poses a durability challenge. The research group fabricated single crystals of Mg₃Sb₂ and Mg₃Bi₂ with precisely controlled carrier density and discovered an extremely unique property (goniopolarity) that leads to the realization of "transverse" thermoelectric modules in which the heat flow and power generation direction are orthogonal. The transverse thermoelectric module does not require electrodes at the high-temperature side of the module, which prevents thermal degradation, and is expected to drastically solve the durability issue that has been the bottleneck of conventional thermoelectric modules.
First-principles calculations were performed to elucidate the origin of the goniopolarity, and it was found that the sign of charge carriers differs depending on the crystallographic direction due to the anisotropy of the electronic structure. Since there are many materials with similar characteristics, the application of the method used in this study is expected to lead to the development of thermoelectric modules with higher performance.

A researcher in AIST, in collaboration with the Centre national de la recherche scientifique (CNRS) of France, has clarified for the first time how pest insects become resistant to disease through the power of gut microbes.
Biological pesticides with low environmental impact are attracting attention in order to achieve sustainable agriculture. Compared to chemical pesticides, biological pesticides (e.g. pathogenic microorganisms of pest insects) can reduce residues harmful to the human body and biodiversity, but to improve their effectiveness in controlling pests, it is still necessary to know more about the immune mechanisms of pests against pathogenic microorganisms. In this study, the authors investigated the immune mechanism of the soybean pest, Riptortus pedestris, and found that some gut microbes break through the epithelial cells of the gut and interact with phagocytes and immune cells (fat body) inside the stink bug, stimulating the systemic immunity. Furthermore, the authors found that stink bugs whose immune systems are activated by gut microbes show a high survival rate even when pathogens infect them. These findings open a new window in the field of insect immunity and are important for improving the insecticidal efficiency of biopesticides.

AIST proposed the general requirements of an international standard for dynamic signs with Mitsubishi Electric Corporation, and the proposal was adopted as ISO 23456-1:2021.
The more effective sign system will be established by developing individual standards under this international standard. We are expecting for the society sharing with various age groups, cultures, and perceptual and physical characteristics, such as the elderly and wheelchair users under the concept of accessibility for all people.

A researcher at AIST has established a method for evaluating free-energy landscape so that it is independent of the representation of the shape.
Free-energy landscape is used in a wide range of fields, such as simulating the expected progress of a reaction of a designed catalyst or predicting drug efficacy and side effects for use in drug development. However, conventional methods derive different free-energy landscapes depending on how the conformational changes of molecules in chemical reactions are represented, and the theoretical basis for quantitative prediction and interpretation has been weak.
In this study, the deformation motion of molecules is expressed by the Langevin equation, which is used to describe Brownian motion. By using the diffusion coefficient that appears in the equation, we succeeded in deriving a free-energy landscape that is independent of the representation of the shape. The results of this research set the theoretical foundation for quantitative discussions of catalytic reactions and protein folding reactions. It is expected that the formulas from this research will be used to provide high quality data on which to base the design of catalysts and pharmaceuticals.

A researcher at AIST, in collaboration with Aichi Steel Corporation, has developed a highly sensitive magnetic sensor that can automatically compensate for fluctuations in detection sensitivity due to manufacturing variations and environmental changes.
Compact, highly sensitive magnetic sensors are needed in a wide variety of applications, including industrial and biological measurement. To apply them to fields such as IoT, their sensitivity must be maintained at a constant level. The cost of manually adjusting sensitivity has hindered the expansion of applications for small, high-sensitivity magnetic sensors.
By combining an application-specific integrated circuit (hereinafter referred to as "ASIC") with an automatic correction function originally designed by AIST and a magnetic impedance element (hereinafter referred to as "MI element") developed by Aichi Steel Corporation, the fluctuation of the magnetic detection sensitivity was reduced to 1/3 of its original level. This automatic calibration technique does not require a special test mode for the process, and can be performed in the background during normal sensing operation. The digital-output architecture achieves both easy handling of output signals and low power consumption. This approach is expected to expand the range of applications for compact, high-sensitivity magnetic sensors.

In 2020, AIST researchers estimated the microbially mediated methane consumption rate by chemical and microbiological analyses coupled with stable isotope tracer experiments of sediments collected from the seafloor off Sakata City, Yamagata Prefecture, where methane hydrates are distributed. They also discovered that in the redox transition zone below the seafloor, methane-oxidizing microorganisms that require oxygen for growth (aerobic methanotrophs) and those that do not (anaerobic methanotrophs) are metabolically active and consume methane. These findings contribute to an accurate understanding of the seafloor budget of methane.

Researchers at AIST, in collaboration with Yokohama National University, used two high-precision atomic clocks, an ytterbium optical lattice clock and a cesium fountain atomic clock, to search for dark matter, which exists in large amounts in the universe but whose true nature remains unknown.
AIST contributes to International Atomic Time, the international standard time, by operating the cesium fountain atomic clock, which realizes the definition of the unit of time "second," and the ytterbium optical lattice clock, one of the candidates for the redefinition of the second, at high operating rates for a long time. The frequency of an atomic clock is determined by fundamental physical constants such as the fine structure constant and electron mass, and the constant and invariant nature of the fundamental physical constants guarantees the accuracy of the atomic clock. On the other hand, it can be said that an atomic clock is an experimental device to verify whether the fundamental physical constants are truly constant and invariant.
Recently, ultra-light dark matter, which is more than 20 orders of magnitude lighter than the electron mass (about 9 × 10^-31 kg), has been proposed as a candidate for dark matter. This very light dark matter behaves as a wave, not a particle. If dark matter waves interact with ordinary matter such as atoms, it is theoretically predicted that the fundamental physical constants will oscillate periodically, which in turn will cause periodic oscillations in the frequency of atomic clocks. In this study, we searched for such periodic oscillations in the frequency ratio data of the ytterbium optical lattice clock and the cesium fountain atomic clock. The results show that there is no such interaction between ultra-light dark matter in the mass range 10^-58 kg to 10^-56 kg and electrons, or if such an interaction exists, its strength is very weak. This result contributes to fundamental physics aimed at understanding dark matter.
Details of this study were published in Physical Review Letters on December 7, 2022.

In support of the development of large-scale superconducting quantum computers, researchers with the National Institute of Advanced Industrial Science and Technology (AIST), one of the largest public research organizations in Japan, in collaboration with Yokohama National University, Tohoku University, and NEC Corporation, proposed and successfully demonstrated a superconducting circuit that can control many qubits at low temperature.
To realize a practical quantum computer, it is necessary to control the state of a huge number of qubits (as many as one million) operating at low temperature. In conventional quantum computers, microwave signals for controlling qubits are generated at room temperature and are individually transmitted to qubits at low temperature via different cables. This results in numerous cables between room and low temperature and limits the number of controllable qubits to approximately 1,000.
In this study, a superconducting circuit that can control multiple qubits via a single cable using microwave multiplexing was successfully demonstrated in proof-of-concept experiments at 4.2 K in liquid helium. This circuit has the potential of increasing the density of microwave signals per cable by approximately 1,000 times, thereby increasing the number of controllable qubits significantly and contributing to the development of large-scale quantum computers.
The above results will be published in “npj Quantum Information” on June 3 at 10 a.m. London time.