EPILOGUESCIENCE, SCIENCE!Yuki YamakawaTechnical Document Administration Section, Technical Development CenterSince joining Rion in 2012, he’s been in-volved in developing sensors for particle counters and has been an active mem-ber of the research project for reducing the minimum measurable particle diameter.ΙθΙ0л4m2(1+cos2θ)1-m22+4λ4d6=2The lovable but frustrating RayleighAfter joining Rion in 2012, I was as-signed in April 2021 to the Technical Docu-ment Administration Section. Before that, I’d been engaged in the development of particle counters at the Technical Develop-ment Center. My area of expertise lies in R&D on sensor components.* *I’ve always loved science and math. I even built a radio for my summer vacation research project in elementary school. I bought the parts in Akihabara and assem-bled them at home. Experiencing how radio waves became sound was fascinat-ing and delightful. I even made a small version of the Denryu Iraira Bou (Irritating Maze) that was popular on TV at the time, where you guide an electric rod through a metal-framed course while trying to avoid contact with the frame. I had a great sci-ence teacher in junior high school who let us do experiments, like mixing chemicals to produce carbon dioxide and making small reworks. I remember preferring chemistry over physics. I loved to learn about what stuff was made of, how they were struc-tured, or what their characteristics or prop-erties were. In senior high school, I joined the swim team and the chemistry club. In college, I majored in biotechnology. I did R&D work on a robot named the Scrub Nurse Robot, which was designed to assist in laparoscopic surgical procedures. I was in charge of the eye part. I loved working on getting the robot to recognize and understand the status and progress of the surgery using UV and infrared light, which humans can’t see.* *Because I’d studied light for a long time, I was overjoyed when I found out Rion had been developing particle count-ers. I’d wanted to work for a medical in-strument manufacturer. My idea of Rion, which is located in an area so familiar to me, was that it dealt mainly in sound and vibration. I’ve heard I was one of the rare job-seeking students who announced, “I’d love to be a member of the particle count-er development team!” [Laughter]After I joined Rion, I participated in developing particle counters. One equa-tion in particular that stayed with me is the Rayleigh scattering approximation. With Rayleigh scattering, particles much smaller than the wavelength of light cause light to scatter. It’s famous for being the phenom-enon responsible for making the sky blue and the sunset red. The colors are the re-sult of Rayleigh scattering by the molecules making up the atmosphere.Because the wavelengths of light re-main relatively unchanged before and after Rayleigh scattering, this equation is always used when developing particle counters.* *When I joined Rion, the minimum measurable particle diameter of particle counters was 40 nm. From there, we tar-geted 30 nm, then 20 nm, and then even smaller sizes. The most important step in developing a particle counter is the simula-tion performed in the initial design phase. We have to determine the conditions for generating the scattered light to obtain sufficiently high signal-to-noise ratios for the particle size in question. And this sim-ulation is based on the Rayleigh scattering approximation.One of the most obvious features of Rayleigh scattering approximation is that the intensity of the scattered light is pro-portional to the 6th power of the particle diameter. In other words, if we halve parti-cle diameter, the intensity of the scattered light is reduced to 1/64. So, if we use a sensor used to measure 40 nm particles to measure 20 nm particles, the intensity of the scattered light will become 1/64, so simple arithmetic says we have to improve the sensor’s performance by a factor of 64. That’s why so little progress has been made in the minimum measurable particle diameter of particle counters. It took nearly eight years for Rion particle counters to achieve the minimum measurable diameter of 20 nm from 30 nm. Instrumental de-velopment takes a long time. I’ve been so exasperated with the equation: “Why does it have to be the 6th power? Why not the 3rd?!” But, anyhow, the Rayleigh scatter-ing approximation does allow us to make precise calculations based on simulations. So looking back, I’d say it’s been a trust-worthy formula.* *What fascinates me the most about light is its potential to carve out a new future. Light is the only quantum humans can sense. Quantum theory is a field of physics where the laws of classical dynamics no longer apply. It’s a field where we can expect further advances.Personally, I’m interested in the sub-stances called metamaterials. They’re arti-cial materials engineered to behave, when exposed to electromagnetic waves, in-cluding light, in ways not observed in nat-urally occurring materials. We can design metamaterials to exhibit optical refractive indices smaller than 1 or even negative. Materials like that would be capable of doing things conventional materials can’t do. For example, 5G and its applications are expanding, but their radio waves have a strong tendency to propagate in straight lines and have problems with obstacles in their path. Here, metamaterial reflectors can be used to get radio waves to circum-vent these obstacles. Research is underway on various other topics. Just thinking about it is exciting. I can’t wait for the future to arrive.No. 004Effort multiplied by 64The Rayleigh scattering approximationIn Rayleigh scattering, which is caused by particles sufficiently smaller than the wavelengths of light, the wavelengths remain nearly unchanged before and after the scattering. The intensity of Rayleigh scattering is given by the equation above.Rion is supported by many science-loving and math-loving staff members. In this series, our science-minded staff members write about their enthusiasm for their respective fields of interest. Part 4 will present the love for and obsession with the Rayleigh scattering approximation.Because We’re Science and Math LoversColumn by Rion’s staff on their obsession with science20Interview and article by Kana Yokota
元のページ ../index.html#22