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A Novel Microsensor for Measurement of Liquid Flow and Diffusivity

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Innovative flow velocity sensor

Unisense is a Danish company, highly specialised in the production of advanced sensor technology for multiple applications in the fields of medicine, biology and environmental studies. The company has recently developed a novel, highly sensitive, microscale sensor for measuring fluid velocities down to 5 microns/second and with a spatial resolution of 10 microns.


This microscale sensor has the form of a tiny glass tube and comprises a tracer reservoir, a silicon membrane and a slim transducer. The transducer, such as gas microsensor is tracer specific and is found within the tracer gas reservoir. The silicon membrane seals off the tip of the tracer reservoir, as it is permeated by the transducer tip. The newly developed sensor is grounded on an innovative concept of a tracer losing its diffusion properties when passing from a reservoir through a membrane-filled pore. These concentration changes reflect flow parameters, including fluid velocity, are detected the transducer tip and the signal is obtained with the aid of picoammeter technology. The sensor's placement is accomplished with suitable positioning equipment that is readily available. Potential tracers are hydrogen, oxygen and acetylene with hydrogen being the best-suited tracer because it allows development of transducer for reliable and fast velocity measurements. In addition, since hydrogen cannot be easily detected in small concentrations, this breakthrough technology may also address problems of measuring hydrogen velocities in such difficult situations. However, the sensor comes in various versions of tracer gas and transducer combinations for meeting different measurement requirements. Compared to other conventionally used methods, such as Laser-Doppler techniques and particle imaging systems, the innovative sensor offers unique advantages. These advantages may lead to extremely lower velocity detection limits (5 microns/second) and spatial resolutions (10 microns). These unparalleled capabilities enable its use for flow studies in various research applications within biology, medicine, physiological research and hydrology.

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