Wobbling tube measures extremely small flow rates
1 min read
Fluid flows as small as 1mg/hr can be measured using a sensor developed by scientists at the University of Twente.
The sensor measures flow using the Coriolis Effect but, unlike traditional instruments, this device is described as a 'wobbling' tube with a diameter of 40µm. Applications are expected to include medical devices.
Fluid passes through a tiny rectangular tube that is made to wobble. The Coriolis effect causes the tube to move upwards and this displacement is a measure of fluid flow.
The researchers say that, until now, wobbling motion has been induced by magnets. However, the magnets would be far bigger than the sensor. Researcher Harmen Droogendijk has developed a method called 'parametric excitation', in which dozens of 'electric fingers' attached to the tube fit between identical opposing fingers mounted on supports running parallel to the tube.
The extent to which these opposing sets of fingers slide between one another can be used to measure lateral displacement. Droogendijk also found there is a limited area of electrical tension in which the tube shows greater movement, although this has to be tuned precisely. Mathematical modelling allowed a new design to be developed that does not need magnets.
Research is now in progress to determine whether even smaller flows can be measured.
Other potential applications include monitoring medical IV pumps, analysing medicines using liquid chromatography and use in microreactors.
