Research projects

The field of fluid engineering has expanded to nanospaces smaller than the light wavelengths. When the space size becomes smaller than 1000 nm, various specific phenomena such as changes of liquid properties appear. Therefore, super-resolution measurements of flow velocity distribution with 10 nm spatial resolution become important for understanding of transport phenomena in nanospaces. In this study, by utilizing spherical aberration, which is a problem in the imaging, we developed defocusing nano-particle image velocimetry (PIV) to determine the position of nanoparticles with 10 nm spatial resolution based on particle images in the defocused region. Characteristics of defocused nanoparticle images with spherical aberration was revealed and a measurement system was constructed. We realized measurements of velocity distribution of nanoparticles migrating with pressure-driven flow in nanospace. This work will greatly contribute to advancements of various fields such as nanofluidics.

10-100 nmのナノ空間の流体科学・工学の進展に伴い、表面支配の極小空間における溶質分子輸送現象の解明が重要となっている。本研究では、独自の技術と方法論に基づき光散乱を用いたナノ空間非蛍光ナノ粒子の超解像度追跡法を創成することを目的とする。サイズと表面粗さを1 nm以下の精度で制御したガラス製ナノ流路を作製して、バックグラウンド光を極限まで低減して光学的に整えた条件下で、ナノ粒子の散乱光と流路壁面からの反射光との干渉により形成される粒子像を高速・高感度に検出し、位相差に伴う粒子像変化からナノ空間を流れる非蛍光ナノ粒子の位置をx, y, zの3方向で10 nm分解能で測定する。

8K対応光学機器の普及に向けて，大口径非球面光学レンズの高能率生産が要求されている．これに応えるため，酸化セリウム（CeO2）スラリーを用いて効率よく延性モード研削を行う，化学反応誘起スラリー援用研削法（RISA研削）の研究を進めてきた．CeO2粒子が砥石表面に付着すると，延性モード研削能力が桁違いに高まる一方で，付着は不安定で，滞留時間の違いによる形状の崩れも生じる．そこで，本研究では，CeO2粒子付着メカニズムを明らかにし，プロセス制御するために感覚機能を備えた超精密加工システムを開発する．これにより，RISA研削の安定化に加え形状制御を実現する．

Nanofluidics utilizing 100 nm spaces has developed and realized analytical methods with ultra-high performances. On the other hand, cells and organelles with sizes similar to micro/nanospaces have various functions, which can not be realized by conventional chemical methods, and cellular membranes have specific roles such as ultra-high selective molecular transport and active transport opposite to the concentration gradient. Therefore, to create new functional devices by incorporating cellular membrane in nanochannels, this study developed a method to form lipid bilayer in nanochannel utilizing our multiphase fluid control technology. Utilizing a nanochannel with partial hydrophobic modification, stable manipulation of parallel two-phase flow was achieved. Based on this fluid operation, we succeeded in formation of lipid bilayer at an interface between two parallel channels with a 4000 nm depth for the first time.

ナノ空間の流体工学の進展により、化学分析の可算個分子レベルへの超微量化が実現しつつある。しかし、試料分子数が限定されても、空間の微小化の単なる延長では流体工学の極限である分子1個の輸送・化学処理とこれにより初めて実現する1分子分析には到達できない。本研究では、独自技術によりナノ流路で極小液滴を生成して、統計力学の原理により液滴中に試料分子1個を閉じ込め個数の単位で配列・輸送、更に液滴の合一により1分子を衝突・反応させる方法論とこれを用いた分析法を創成し、病変部の表皮角化細胞、涙液、汗などに含まれるサイトカイン分析に応用することを目的とする。

Microfluidics has rapidly developed to miniaturize and integrate various fluidic operations. Recently, it has been further downscaled to nanofluidics. In this study, in order to understand fluid flows in ultrasmall nanospaces, we proposed a measurement method of flow velocity distribution by tracing the motion of single-molecules in fluid flows, which we call molecular image velocimetry (MIV). A tracer molecule with controlled size was developed by fluorescence modification of dendrimer, and applied to measurements of pressure-driven flow in a nanochannel. The proposed method and obtained knowledge will contribute to understand fluid dynamics and molecular transport in nanospaces.

Analytical methods utilizing small spaces, as represented by micro and extended-nano fluidic devices, have been developed. We have developed thermal lensing microscope (TLM) and photothermal optical phase shift (POPS) detection to detect non-fluorescent molecules in small spaces with high sensitivity. However, the UV-excitation POPS detection has some problems such as heat dissipation in the extended-nano channel and insufficient reduction of optical background due to interference, which hinders measurements with high sensitivity as TLM. In this study, we developed an extended-nano fluidic device with an integrated thermo-optic layer to recover the sensitivity loss due to the thermal diffusion and a background-free POPS detector to achieve ultrahigh sensitivity.