Direct Generation of a Voltage and Current by Gas Flow Over Carbon Nanotubes and Semiconductors

We report here a direct generation of measurable voltages and currents when a gas flows over a variety of solids even at the modest speed of a few meters per second. The underlying mechanism is an interesting interplay of Bernoulli’s principle and the Seebeck effect: Pressure differences along streamlines give rise to temperature differences across the sample; these in turn produce the measured voltage. The electrical signal is quadratically dependent on the Mach number M and proportional to the Seebeck coefficient of the solids. Results are presented for doped Si and Ge , single wall and multiwall carbon nanotubes, and graphite. Our results show that gas flow sensors and energy conversion devices can be constructed based on direct generation of electrical signals.