Nanofluidic Analytical Platform Utilizing Nanocapillary

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.