The University of Tokyo · Engineering
Professor Kyojiro Morikawa's research lab specializes in the electronic and nanoscale properties of complex oxides and confined liquids, with a focus on strongly correlated electron systems and nanofluidic phenomena. The lab investigates Mott insulators and metal-insulator transitions in perovskite oxides using advanced spectroscopic techniques such as photoemission and inverse photoemission, revealing the interplay between electron correlation and electronic structure. In parallel, the lab pioneers experimental methods to probe liquid behavior in extended nanospaces (10–1000 nm), particularly the dielectric and electrokinetic properties of water and ions in nanochannels, using streaming potential measurements. These studies bridge fundamental physics with applications in nanofluidics, single-molecule detection, and functional nanodevices.
Figures are computed from collected data and may differ slightly.
We have studied metallic ${\mathrm{SrVO}}_{3}$ and ${\mathrm{CaVO}}_{3}$ by inverse photoemission and high-resolution photoemission. In going from Sr to Ca, considerable spectral weight is transferred from the coherent band to the upper and lower Hubbard bands. Meanwhile, the overall intensity rather than the width of the coherent band decreases, implying that the bandwidth remains finite as the system approaches the Mott transition. The result implies that the effect of long-range Coulomb inter
We have studied ${\mathrm{Y}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Ca}}_{\mathit{x}}$${\mathrm{TiO}}_{3}$ by photoemission and inverse-photoemission spectroscopy. Valence-band photoemission spectra show a d-band peak \ensuremath{\sim}1.4 eV below the Fermi level (${\mathit{E}}_{\mathit{F}}$), which evolves into the lower Hubbard band in the x= 0 (${\mathit{d}}^{1}$) limit. The spectra show quasiparticle emission at ${\mathit{E}}_{\mathit{F}}$ with an extremely small spectral weight, z\
The extended-nanospace, a space on the scale of 10(1)-10(3) nm, is mostly unexplored due to the lack of sufficient experimental technology. Recently, the research of liquid properties in the extended-nanospace has gathered much interest, because the behavior of water molecules in this space is between that of liquid-like bulk phase water molecules and single molecules. Due to the large surface-to-volume ratio in the channel, the surface charge of the wall directly affects the water structure and
Nanofluidics have recently attracted significant attention with regard to the development of new functionalities and applications, and producing new functional devices utilizing nanofluidics will require the fabrication of nanochannels. Fused silica nanofluidic devices fabricated by top-down methods are a promising approach to realizing this goal. Our group previously demonstrated the analysis of a living single cell using such a device, incorporating nanochannels having different sizes (10<sup>
Understanding liquid structure and the electrical properties of liquids confined in extended nanospaces (10–1000 nm) is important for nanofluidics and nanochemistry. To understand these liquid properties requires determination of the dielectric constant of liquids confined in extended nanospaces. A novel dielectric constant measurement method has thus been developed for extended nanospaces using a streaming potential method. We focused on the nonsteady-state streaming potential in extended nanos
Nanofluidics, a discipline of science and engineering of fluids confined to structures at the 1-1000 nm scale, has experienced significant growth over the past decade. Nanofluidics have offered fascinating platforms for chemical and biological analyses by exploiting the unique characteristics of liquids and molecules confined in nanospaces; however, the difficulty to detect molecules in extremely small spaces hampers the practical applications of nanofluidic devices. Laser-induced fluorescence m
Isoelectric points in extended nanochannels (580-2720 nm) fabricated on fused-silica substrates were measured using the streaming current method. The isoelectric point obtained in a 2720 nm channel was almost the same as the isoelectric point reported for the bulk (2.6-3.2). However, the isoelectric point in the extended nanochannel (580 nm) was decreased to less than 2.0. This result provides important information for the modeling of ion transport in extended nanospace.
Abstract Channel fabrication technology has become increasingly important for microfluidic and nanofluidic devices. In particular, glass channels have high chemical and physical stability, high optical transparency, and ease of surface modification, so that there is increasing interest in glass microfluidic devices for chemical experiments in microfluidics and nanofluidics. For the fabrication of glass channels, especially those with a high aspect ratio (depth/width), lithography using a metal r
In microfluidics, especially in nanofluidics, nanochannels with functionalized surfaces have recently attracted attention for use as a new tool for the investigation of chemical reaction fields. Molecules handled in the reaction field can reach the single-molecule level due to the small size of the nanochannel. In such surroundings, contamination of the channel surface should be removed at the single-molecule level. In this study, it was assumed that metal materials could contaminate the nanocha
Abstract The bonding of glass substrates is an important process in the fabrication of glass micro/nanofluidic devices. In this study, the influence of the surface roughness of glass substrates after low-temperature bonding is investigated. It is found that plasma etching can be used to control the surface roughness to the range 2–9 nm. Substrates with a roughness of 5 nm or less can be bonded. The pressure capacity of devices tends to decrease with increasing surface roughness. A pressure capac
Abstract In micro- and nanofluidic devices, highly precise fluidic control is essential. Conventional mechanical valves in microchannels and nanochannels have size limitations, whereas hydrophobic (Laplace) valves are generally difficult to use for low-surface-tension liquids. In the present study, we developed a method for handling picoliter volumes of low-surface-tension liquids in a micro-nanofluidic device. The proposed Laplace valve is based on the pinning effect. A fused silica micro-nanof
Understanding the surface properties and related liquid properties in 102 nm spaces (extended nanospaces) is critical for future device engineering. To this end, we used trivalent ions to investigate the charge inversion phenomenon in extended nanospaces. The charge inversion points in bulk didn't substantially differ between a La(NO3)3 solution and a Lu(NO3)3 solution. However, the charge inversion point of a La(NO3)3 solution in extended nanochannels shifted toward the higher-concentration reg
Abstract Studies on novel devices utilizing characteristics of confined geometries have attracted much attention. In particular, a 10–1,000 nm space (extended nanospace) has been expected to establish superior chemical analysis systems in liquid phases, because it not only bridges the methodological gap between conventional nanotechnology and microfluidic technology, but also the scientific one between single molecules and the bulk condensed phase. Therefore, engineering, fluidics, and chemistry
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