Precise control over gas delivery is achieved at the micro and nanobar mass levels by incorporating blocks of aligned carbon nanotubes into valves and finely adjusting the flow through the block by controlling a compressing force applied to the block. A valve for controlling gas flow includes: a valve housing; a block of aligned carbon nanotubes, the block and the valve housing being configured to direct the gas through the carbon nanotubes in the block; and a device configured to apply a force to the block in order to compress the block, wherein the block is compressed perpendicular to the walls of the carbon nanotubes in the block; whereby the application of the force to the walls restricts the flow of the gas through the valve. The valve may further comprise an electrical device for monitoring the electrical properties of the carbon nanotube block. This monitoring provides information on the state of compression of the carbon nanotube block and/or the gas that is flowing through the valve.