RESEARCH
❏ Low-Dimensional Nanomaterial
R. P. Feynman (1918-1988)
Novel Prize in Physics (1965)
Richard Feynman, known as a pioneer in nanotechnology research, pointed out in his lecture titled "There's Plenty Room at the Bottom" that the world at the tiny "bottom" scale offers abundant unknown possibilities, encouraging scientists and engineers to explore them. In fact, many Nobel Prizes have been awarded for research on nanomaterials to date, making it one of the most active research fields.
Two-dimensional functional atomic thin films (hereinafter referred to as 2D materials) are layered atomic thin films consisting of one or more layers. Compared to conventional materials, they are extremely thin, have a large surface area, and exhibit unique electrical, optical, and mechanical properties, leading to expectations of innovative advances in next-generation electronic devices, electronics, energy conversion, biosensing, and other fields. This research aims to develop innovative synthesis techniques to overcome the challenges in conventional synthesis methods.
Moreover, realizing "van der Waals heterostructures (vdWH)" combining 2D materials such as graphene and hBN would create a significant expansion in various aspects, including overlaps and twists between 2D materials with different compositions, spacing between layers, and integration of 2D materials with materials of other dimensions. We aim to pioneer the realization of unexplored nanomaterials and create innovative technologies for the future
(1) Development of Graphene Biosensors
Graphene possesses unique properties such as extremely high electron mobility, large surface area, and stability in water. By directly contacting target substances such as viruses with the large exposed surface of graphene in water, it is possible to extract a large current change as a result of carrier modulation. Therefore, graphene is highly promising as a material for high-sensitivity biosensors and bioanalysis platforms.
(2) Development of DNA Sequncing Devices
Nanopore sequencing is a molecular biology technique that determines the sequence of bases by passing DNA or other biomolecules through individual nanopores (tiny pores) and analyzing the resulting current changes. Nanopore sequencing has a wide range of applications in fields such as genomics, cancer diagnostics, and rapid diagnosis of infections, due to its characteristics such as single-molecule sequencing, high-speed real-time data acquisition, and long read lengths. Nanopores composed of materials such as graphene and MoS2 have higher resolution, stability, and durability compared to conventional nanopore technologies. However, challenges remain in detecting biomolecules at the single-molecule level due to the fast passage of biomolecules through the pore and clogging of the pore due to the hydrophobic nature of the materials and interaction with biomolecules. The vdWH structure consisting of hBN/graphene/hBN is expected to prevent hBN from adhering to the DNA membrane surface and delay the passage time, which could improve the detection of biomolecules.
(3) Development of vdWH-Type Ultra-High-Speed FETs
In the Beyond 5G era of the 2030s, it is anticipated that the access communication speed and the number of connected devices will be 10 times higher than that of 5G, the core communication speed will be 100 times higher than that of the current technology, and achieving precise synchronization between cyberspace and physical space will require 1/10th the latency and 1/100th the power consumption of 5G. Two-dimensional materials with high carrier mobility and high-density characteristics are ideal for high-speed and efficient signal processing, making them suitable for achieving ultra-high-speed and ultra-low-power consumption communication. The application and development of innovative devices and nanosystems using heterostructures composed of two-dimensional functional atomic thin films, including graphene and hBN nanosheets, aim to create next-generation sensing devices beyond conventional principles, contributing significantly to scientific and technological innovation.
(4) Development of PEM for Solid Polymer Fuel Cells
Hydrogen is gaining recognition as a key player in energy strategies for achieving a decarbonized society, as it enables energy storage for applications such as batteries and reduces carbon dioxide emissions. The market for hydrogen fuel cell vehicles, which apply hydrogen energy to the mobility sector, is estimated to grow globally from $11.7 billion in 2020 to $469 billion by 2028. Hydrogen fuel cell vehicles are more efficient than gasoline engine vehicles and hybrid vehicles, requiring high technical expertise for development. Therefore, they are important for Japan's next-generation energy strategy, given the country's energy self-sufficiency rate of less than 15%. However, the development of solid polymer electrolyte membrane (PEM) fuel cells for use in hydrogen fuel cell vehicles has been hindered by performance degradation over long-term use. To address this issue, it is essential to develop a PEM for solid polymer fuel cells that can stably withstand long-term use while maintaining high efficiency. hBN nanosheets have high proton conductivity and gas barrier properties against most gases, including H2 and O2, which could significantly improve the efficiency of fuel cells. Furthermore, they have advantages such as high thermal stability, chemical stability, excellent mechanical properties, and electrical properties, making them capable of withstanding long-term use.
Two-dimensional materials often exhibit properties distinct from traditional materials, and their detailed elucidation is limited by experiments alone. Theoretical computational science is highly useful in this regard. Representative computational methods such as first-principles calculations and molecular dynamics simulations, when combined with experimental approaches, enable rapid predictions and designs that experiments alone cannot achieve, making them crucial in the study of two-dimensional materials. In this study, we aim to construct more accurate and advanced theoretical models by mutually feeding back synthesis experiments and computational science, ultimately leading to device development.
❏ Functional Thin Film and Tribology
Wolfgand Pauli (1900-1958)
Novel Prize in Physics (1945)
Since ancient Egypt, people have been trying to understand and technologically control surfaces, but, as the great physicist Pauli remarked, there are few things as difficult to understand as surfaces, despite being so close to us. In our laboratory, we aim to develop technology to improve surface properties using functional thin films such as Diamond-Like Carbon (DLC).
Functional hard carbon films such as DLC (Diamond-Like Carbon film) are being used for surface treatment of automotive engine parts, tools, molds, and other components due to their excellent properties of low friction, wear resistance, release properties, and corrosion resistance. However, most mechanical parts have three-dimensional shapes, and with conventional film formation technologies, uniform surface modification for complex three-dimensional mechanical parts is extremely difficult. Furthermore, when the size of the coated object becomes nanometer scale, achieving a uniform three-dimensional coating becomes nearly impossible. In the future, for the practical application of nanomachines and the advancement of nanoimprint technology, the longevity of the drive parts of nanomachines and the high reliability of nanoimprint transfer patterns are essential. In this study, we aim to establish a three-dimensional nano-surface modification method by controlling the behavior of carbon ion flow in three-dimensional nano-space using simulation methods.
Increased attention is being paid to energy conservation and environmental issues such as global warming and depletion of energy resources. Currently, friction losses in sliding parts such as automobiles and machine tools are estimated to be tens of trillions of yen annually. Reducing friction losses has a significant impact on energy conservation and is a major concern. From the perspective of environmental pollution, efforts are being made to reduce the use of extreme pressure additives in sliding components and oils and greases used during cutting, as well as solvents used for cleaning them. Therefore, the development of sliding technologies using environmentally friendly and biodegradable lubricants is urgently needed. Against this background, surface modification using hard functional thin films such as diamond-like carbon (DLC) is useful as a method to realize next-generation sliding technologies. In this study, we evaluate the friction properties of 3D ta-C films on actual gears and under biodegradable lubrication using an FZG gear test machine. We aim to pioneer the world's first 3D superlubricity phenomenon with a friction coefficient of 0.005 in gear actual machine tests. This research is being conducted in collaboration with Komatsu's Innovation and Technology Co-Creation Institute
