Quantitative Detection and Fixation of Single and Multiple Gold Nanoparticles on a Microfluidic Chip by Thermal Lens Microscope

A detection and fixation method of single and multiple gold nanoparticles on the wall of a microfluidic channel is demonstrated. A thermal lens microscope (TLM) with continuous-wave excitation (wavelength, 532 nm) and probe (wavelength, 670 nm) laser beams was used to realize the sensitive detection of heat generated by light absorption of individual gold nanoparticles (50 nm in diameter); fixation of the individual nanoparticles was realized simultaneously. The fixation mechanism was investigated and attributed to an absorption-based optical force. In addition to single nanoparticle detection, multiple-nanoparticle detection and fixation was demonstrated. An acceleration of fixation was observed when the number of fixed particles was increased. TLM is expected to be a powerful tool for both the quantitative detection and precise fixation of individual nanoparticles

Integration of Flow Injection Analysis and Zeptomole-Level Detection of the Fe(II)-<i>o</i>-Phenanthroline Complex

Microchannels having a 150×100 µm cross section were fabricated in a quartz glass chip as a component in an integrated flow injection analysis (FIA) system. They were put to use for flow, mixing, reaction, and detection. The reaction system was a chelating reaction of divalent iron ion with o-phenanthroline (o-phen), and a photothermal microscope was applied for the ultra-sensitive detection of the non-fluorescent reaction product. Nano liter levels of solutions were introduced and transported by capillary action and mixed by molecular diffusion. Zeptomole levels of the reaction product were detected quantitatively. This was the first demonstration of an on-chip chemical determination device which integrates the primitive FIA system without using electroosmotic liquid control or fluorometric determination

Molecular Transport between Two Phases in a Microchannel.

Today, microfabricated devices (microchips) have attracted considerable attention because of their vast applicability and versatility. Most published reports utilizing microchips to separate and detect analysis of interest have concentrated on using electrokinetically driven separation schemes. Investigations from a different standpoint have been few in number. However, microchips offer advantages concerning the scale merits of microspace, such as a short diffusion distance and the high interface-to-volume ratio, the specific interface area; we thus considered that they are an ideal tool to study molecular transport between two different phases, i.e., solvent extraction. In the present paper, we report on the first demonstration using a microchip to study molecular between two phases

Integrated Multilayer Flow System on a Microchip.

We utilized microchip technology and found that the multilayer flow of liquids can be formed in microchannels. Liquid/liquid interfaces were formed parallel to the side wall of the microchannels, because the surface tension and friction force are stronger than the force of gravity. A water/ethylacetate/water interface was formed in a 70-µm-wide and 30-µm-deep channel. The interface was observed to be quite stable and to be maintained for a distance of more than 18 cm. As an example of a multilayer flow application, we demonstrated the liquid/liquid extraction of Co-dimethylaminophenol complex in a microchannel. The solvent-extraction process of the complex into m-xylene in the multilayer flow was found to reach equilibrium in 4 s, while it took 60 s in a simple two-phase extraction

液体における光音響分光法の基礎理論と分析化学及び分屈学への応用

University of Tokyo (東京大学