28-08-2017, 01:14 PM
The direct generation of measurable voltages and currents is possible when a fluid flows over a variety of solids even at the modest velocity of a few meters per second. In the case of the underlying gases mechanism is an interesting interaction of the Bernoulli principle and the See Beck 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 number of Mach M and proportional to the Seebeck coefficient of the solids.
This discovery was made by Professor Ajay Sood and his student Shankar Gosh of IISC Bangalore, who had previously discovered that the flow of liquids, even at low speeds ranging from 10 -1 meters / second to 10 -7 m / s Say, more than six orders of magnitude), through bundles of straw-like atomic-scale carbon tubes known as nanotubes, generated tens of microvolts through the tubes in the direction of liquid flow.
The results of the experiment by Professor Sood and Ghosh show that gas fault sensors and energy conversion devices can be constructed based on the direct generation of electrical signals. The experiment was performed on single wall carbon nanotubes (SWNT). This effect is not limited to single nanotubes that are also observed in doped semiconductors and metals.
The observed effect immediately suggests the next application of technology, namely gas flow sensors to measure gas velocities from the generated electrical signal. Unlike existing gas flow sensors, which are based on heat transfer mechanisms from an electrically heated sensor to the fluid, a device based on this newly discovered effect would be an active gas flow sensor that gives a direct electrical response To the gas flow.
One of the possible applications may be in the field of aerodynamics; Several local sensors could be mounted on the body or aerodynamic profile of the aircraft to measure the aerodynamic speeds and the effect of the drag forces. Energy conversion devices can be built based on the direct generation of electrical signals, ie if one is able to cascade millions of these electric power tubes can be produced.
As the state of the art advances toward the atomic scales, detection presents a major obstacle. The discovery of carbon nanotubes by Sujio Iijima in NEC, Japan in 1991 has provided new channels for this purpose. A carbon nanotube (CNT) is a sheet of graphene that has been rolled up and capped with fullerenes at the end. Nanotubes are exceptionally strong, have excellent thermal conductivity, are chemically inert and have interesting electronic properties that depend on their chirality. The main reason for the popularity of CNTs is their unique properties. The nanotubes are very strong, mechanically robust and have a high Young's modulus and aspect ratio. These properties have been studied experimentally, as well as using numerical tools. Bandgap of CNTs is in the range of 0 ~ 100 meV, and therefore can behave like metals and semiconductors.
Many factors such as the presence of a chemical species, mechanical deformation and magnetic field can cause significant changes in the band gap, which consequently affects CNT conductance. Its unique electronic properties, together with its strong mechanical resistance, are used as several sensors. And now with the discovery of a new voltage-induced voltage property exhibited by nanotubes recently discovered by two Indian scientists, another dimension was added to micro-sensor devices.
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 number of Mach M and proportional to the Seebeck coefficient of the solids.
This discovery was made by Professor Ajay Sood and his student Shankar Gosh of IISC Bangalore, who had previously discovered that the flow of liquids, even at low speeds ranging from 10 -1 meters / second to 10 -7 m / s Say, more than six orders of magnitude), through bundles of straw-like atomic-scale carbon tubes known as nanotubes, generated tens of microvolts through the tubes in the direction of liquid flow.
The results of the experiment by Professor Sood and Ghosh show that gas fault sensors and energy conversion devices can be constructed based on the direct generation of electrical signals. The experiment was performed on single wall carbon nanotubes (SWNT). This effect is not limited to single nanotubes that are also observed in doped semiconductors and metals.
The observed effect immediately suggests the next application of technology, namely gas flow sensors to measure gas velocities from the generated electrical signal. Unlike existing gas flow sensors, which are based on heat transfer mechanisms from an electrically heated sensor to the fluid, a device based on this newly discovered effect would be an active gas flow sensor that gives a direct electrical response To the gas flow.
One of the possible applications may be in the field of aerodynamics; Several local sensors could be mounted on the body or aerodynamic profile of the aircraft to measure the aerodynamic speeds and the effect of the drag forces. Energy conversion devices can be built based on the direct generation of electrical signals, ie if one is able to cascade millions of these electric power tubes can be produced.
As the state of the art advances toward the atomic scales, detection presents a major obstacle. The discovery of carbon nanotubes by Sujio Iijima in NEC, Japan in 1991 has provided new channels for this purpose. A carbon nanotube (CNT) is a sheet of graphene that has been rolled up and capped with fullerenes at the end. Nanotubes are exceptionally strong, have excellent thermal conductivity, are chemically inert and have interesting electronic properties that depend on their chirality. The main reason for the popularity of CNTs is their unique properties. The nanotubes are very strong, mechanically robust and have a high Young's modulus and aspect ratio. These properties have been studied experimentally, as well as using numerical tools. Bandgap of CNTs is in the range of 0 ~ 100 meV, and therefore can behave like metals and semiconductors.
Many factors such as the presence of a chemical species, mechanical deformation and magnetic field can cause significant changes in the band gap, which consequently affects CNT conductance. Its unique electronic properties, together with its strong mechanical resistance, are used as several sensors. And now with the discovery of a new voltage-induced voltage property exhibited by nanotubes recently discovered by two Indian scientists, another dimension was added to micro-sensor devices.