1. Motivation / Overview
Nanofluidics is a rapidly emerging and important research field in nano-bio science and technology1. Despite its importance, liquid properties at the nano-scale are not fully understood. There have been several efforts to define and control nano-scale fluidic behavior by making nanochannels2. However, they suffer from difficulties in controlling the extrusion fluid of the liquid and defining nanofluidics through nano-aperture in ambient conditions due to external high atmospheric pressure coming from the geometry of nano-constructions. Here, we first demonstrate nano-scaled liquid extrusion through a nano-aperture pipette (30 nm) based on the optical microscope combined quartz tuning fork – atomic force microscopy (OM QTF-AFM) system in ambient conditions3.
* References
1. W. Sparreboom, A. van den Berg and J. C. T. Eijkel, “Principles and applications of nanofluidic transport”, Nature Nanotech. 332, 713-720 (2009) [Link]
2. Nevin Naguib, Haihui Ye, Yury Gogotsi, Almila G. Yazicioglu, Constantine M. Megaridis, and Masahiro Yoshimura,”Observation of water confined in nanometer channels of closed carbon nanotubes”, nano Lett. 4, 2237-2243 (2004) [Link]
3. F. J. Giessibl, “Advances in atomic force microscopy”, Rev. Mod. Phys. 75, 949-983 (2003) [Link]
2. Nanopipette – Pulled Nanopipette
A pencil-shaped nano-aperture glass pipette which was fabricated using thermal heating followed by mechanical pulling (P-2000, Sutter Instrument Co.)
When dye molecules pass through the nano-aperture, the dye molecules are aggregated by the interplay of hydrophobic and electrostatic interactions. The aggregates were small enough to pass through the 30 nm aperture, but it was difficult to define their sizes using a fluorescence microscope because of the blowing effect.
3. Experimental Setup
Using the naturally formed capillary condensation on the apex of the nanopipette, the filled liquid inside the nanopipette can be connected and ejected onto the outside surface by an applied electric field between the inserted electrode inside the nanopipette and the substrate.
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