The Nanogate: nanoscale flow control

Abstract

The handling of extremely small samples of gases and liquids has long been a subject of research among biologists, chemists and engineers. A few scientific instruments, notably the surface force apparatus, have been used extensively to investigate very short-range molecular phenomena. We report the design, fabrication and characterization of an easily manufactured gas and liquid flow control device called the Nanogate. The Nanogate controls liquid flows under very high planar confinement, wherein the liquid film is, in one dimension, on the scale of nanometers, but is on the scale of hundreds of microns in its other dimensions, as shown in Figure 1. The fluid film thickness can be controlled within 2 /spl Aring/, from sub-10 nm up to 1 micron. Control of helium gas flow rates in the 10/sup -9/ atm.cc/s range, and sub-nl/s flow rates of water and methanol have been predicted and experimentally verified. The Nanogate incorporates an external piezoelectric actuator as a displacement source. The gap thickness is directly measured with external optical metrology.