In analysis and medical diagnosis, there is an increasing demand for small-volume analysis such as single-cell, exosome, and molecule analysis. For this, an analytical platform for those small-volume samples is needed. In particular, the nanofluidic channel is one of the promising formats; however, the fabrication is complicated and limits the applications. In this study, we developed a nanofluidic analytical platform utilizing nanocapillary, requiring no complex nanofabrication. The challenge is connecting nanocapillary with microfluidic channels without dead volume. To solve this issue, a novel connector was designed. The dead volume was only 125 pL, representing a 71-fold decrease from conventional systems (8.8 nL). The platform demonstrated significant improvement in fluid transition time from several hours to 300 seconds in 235 nm capillaries. Using this platform, we investigated water viscosity behavior in circular nanocapillaries (235-1380 nm). Our results revealed a 2.5-fold increase in water viscosity within 235 nm capillaries compared to 1380 nm channels, while maintaining consistent surface interactions across all diameters (contact angle: 76.15°±2.74°). Based on the results, the uniform geometry of circular capillaries enabled a clear investigation of fluid properties under nanoscale confinement. This prospective method will be widely applied to biomedical applications and medical diagnosis.

Capillary microfluidics employs surface tension to manipulate liquids without requiring peripheral equipment, rendering it a convenient and robust approach for managing complex microfluidic circuits. However, most capillary microfluidics are applied only to aqueous solution introduction. This study introduces the capillary introduction of a mixture of black ink and a prepolymer liquid of polydimethylsiloxane (black PDMS liquid). The behavior of the black PDMS liquid during capillary introduction was investigated in straight, open-ended PDMS microchannels. The surface tension of the liquid was determined using the pendant drop method as 20.9±0.1 mN/m. The contact angle of the black PDMS liquid on the solidified PDMS plate surface was measured from liquid flow images, revealing a dependence on the liquid flow velocity. A simplified flow model was proposed, assuming that the viscosity of the black PDMS liquid depended on its velocity and the viscosity was dependent on the shear rate to the power of -0.682. Building on the fundamental aspects of capillary flow, the introduction of black PDMS liquid into the patterned microchannel was successfully realized. This fundamental knowledge of the capillary introduction of PDMS liquid is expected to facilitate advancements in microsystems with specific patterns and applications.

Cannabinoids found in cannabis plants include substances designated as narcotics as well as those used in health care and beauty products, highlighting a strong demand for the development of technology to easily distinguish and detect them. However, these compounds have similar chemical structures, making it challenging to differentiate them with simple analyses. We have developed a paper-based microfluidic device capable of distinguishing and detecting tetrahydrocannabinol (THC) and tetrahydrocannabinolic acid (THCA), which are designated as narcotics, as well as cannabidiol (CBD) and cannabinol (CBN), which are used in health care and beauty products. By reacting each of these cannabinoids with a diazo coupling reagent, capturing the resulting colorimetric products with a digital camera, and analyzing the images, this device can distinguish and detect the four cannabinoids.

In this study, as part of a broader investigation of micro-paper-based analytical devices (microPADs), we verified whether it was possible to measure the electrical resistivity of human blood samples using paper-based chips designed for electrical resistivity measurement. We also aimed to investigate the correlation between electrical resistivity and whole blood viscosity, the latter being calculated from the hematocrit value of blood and the total protein value of serum.

This study introduces an automated enzyme-linked immunosorbent assay (ELISA) system employing a novel dip methodology. Unlike traditional ELISA, which requires complex liquid handling, this approach keeps samples and reagents stationary while immersing antibody-coated reaction fields sequentially. This design eliminates pumps and tubing, reducing maintenance, reagent waste, and overall costs. The system, controlled via a microcontroller and web-based interface, demonstrated accurate and efficient C-reactive protein analysis in human serum. With reduced reagent volumes, lower operational costs, and simplified handling, this system offers significant potential for point-of-care testing, telemedicine, and broader next-generation healthcare applications.

High-throughput culture of actinomycetes using commercially available micro-droplets is difficult because the elongated mycelium penetrates other microdroplets and destroys them. In this study, we developed a microwell with independent micro-spaces and succeeded in culturing actinomycetes while maintaining them in each micro-space. We also assessed their growth behavior by continuously analyzing the autofluorescence of the same cells.

The polymerase chain reaction (PCR) is widely used for the detection of specific sequences of DNAs. PCR can easily amplify the target DNAs; however, PCR requires a labeling procedure for the detection of amplified DNAs. In this study, label-free detection of amplified DNAs based on localized surface plasmon resonance (LSPR) using gold layer deposited plasmonic crystal (PC) was developed. Label-free detection of amplified DNAs by PCR was carried out on the PC, and the LSPR optical characteristics change was monitored. As a result, the possibility of label-free detection of DNAs using PC was successfully suggested.