Although similar "gas-flow sensors" are currently being used for a variety of industries, the new sensor is the first that works on the scale of micrometers and nanometers, or millionths and billionths of a meter, respectively, said Steven Wereley, an associate professor of mechanical engineering.
Gas-flow sensors currently used, including those in residential gas meters to determine how much to charge customers, operate on a principle known for at least 100 years. According to that principle, as gas flows over a surface, such as the wall of a pipe or an object flying through the air, molecules of gas nearest the surface remain stationary. The molecules farther away from the surface move progressively faster.
"That model works really well in many situations, including aerodynamics and applications where the scale of the flow is large compared to the size of the molecules," Wereley said.
This principle, however, does not apply to gas flowing through channels on the scale of micrometers or nanometers, meaning ordinary designs will not work for sensors needed for applications on those scales. In such applications, gas molecules immediately adjacent to the wall of a tube do flow and are said to "slip."
"This exception to the model carries important design implications," Wereley said.
Findings will be detailed in a research paper to be published in the February issue of the Journal of Micromechanics and Microengineering. The paper was written by Wereley and Jaesung Jang, a postdoctoral research associate in Purdue's School of Electrical and Computer Engineering.
The paper describes how the sensor is designed.
As gas flows through a tiny channel, some of it is diverted into a reservoir, where it pushes against a silicon diaphragm coated with metal. As the diaphragm balloons outward from the pressure of the gas, it comes close to an electronic device called a capacitor, which stores an electric charge. The closer it comes to the capacitor, the more it affects the capacitance in the device. The changing capacitance is related to a difference in pressure, and a mathematical model is then used to precisely measure how much gas is flowing through the sensor based on the changing pressure.
Because of the channel's diameter, which is 128 microns, barely wider than a human hair, it is extremely sensitive to small gas flows, Wereley said.
Gas-flow sensors that operate on the scale of micrometers and nanometers could have applications in environmental protection, particularly to measure the leakage of hydrocarbon fumes from fuel tanks in new cars on the manufacturing line. Federal environmental guidelines specify how much leakage is allowable.
Automakers currently test empty fuel tanks by pressurizing them with a gas, such as helium, and then measuring whether the pressure drops, indicating leakage. The test is limited because, while it can determine whether a tank is leaking, it cannot reveal how severe the leak is. Using a sensor capable of measuring gas flow on small scales would make it possible to yield more accurate data.
An accurate test also could be applied to the pharmaceutical industry, which preserves drugs in packages filled with a gas free of the molds and impurities of ambient air. Pharmaceuticals are shipped and stored in the packaging, and the industry tests packages for leakage, but gas-flow sensors could be used to test them more accurately.
The Purdue researchers worked with industry to develop the sensors, which currently are too costly to be manufactured profitably. The research is associated with the Microfluidics Laboratory at the Birck Nanotechnology Center in Purdue's Discovery Park.
The research, which has concluded, was funded by the Indiana 21st Century Research and Technology Fund and Advanced Test Concepts Inc. in Indianapolis.
Writer: Emil Venere, (765) 494-4709, firstname.lastname@example.org
Source: Steven Wereley, (765) 494-5624, email@example.com
Purdue News Service: (765) 494-2096; firstname.lastname@example.org
Emil Venere | EurekAlert!
Basque researchers turn light upside down
23.02.2018 | Elhuyar Fundazioa
Attoseconds break into atomic interior
23.02.2018 | Max-Planck-Institut für Quantenoptik
A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.
In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...
A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.
By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...
Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
23.02.2018 | Physics and Astronomy
23.02.2018 | Health and Medicine
23.02.2018 | Physics and Astronomy