Nanofluidic gas/liquid switching utilizing a nanochannel open/close valve based on glass deformation

Abstract

There has been much progress in the field of nanofluidics, and novel applications, such as single-cell analysis, have been achieved. In such cases, controlling the location of the gas/liquid interface is vital and partial hydrophobic modification is frequently used to pin the position of this interface. However, because the fluid manipulating pressure in such devices is comparable to the Laplace pressure at the interface of approximately 0.1 MPa, the interface cannot be maintained stably. The present work demonstrates a method of controlling the gas/liquid interface using a hydrophobic nanochannel open/close valve. The high Laplace pressure at this valve (on the order of 1 MPa) fixes the location of the interface even during fluid manipulation. In addition, the interface can be moved at any time simply by closing the valve to generate an impulsive pressure higher than the Laplace pressure. A device incorporating this nanochannel open/close valve was fabricated, and the surface of the valve chamber was modified with hydrophobic molecules. Gas/liquid replacement in association with the operation of this valve was verified using microscopic observations. It was verified that this replacement was triggered by the valve operation, with a replacement time of 1.2 s. Using this process, gas/liquid switching can be performed when desired and this control method could expand the use of gas/liquid two-phase systems to realize further integration of chemical processes in nanofluidics.