Measuring and weighing without contact

Particularly in cleanrooms, surfaces must be sealed, and be able to be easily and effectively cleaned and disinfected. The items of apparatus present the biggest challenge here: from test tubes to distillation columns, they are introduced from the outside and can bring in germs. Moreover, the contact surfaces on their bases develop minute cracks that are difficult to keep clean. The use of levitation technology based on magnetic fields – for example superconductor technology – can dispense with such problems in future.

SupraSensor: measuring and weighing without contact

One of the many possibilities is shown by the SupraSensor, an application-oriented exhibit presented by Festo at the Anuga Foodtec 2018 trade fair. It demonstrates the function of a contactless balance, which could be used for example on sterile workbenches in biological or chemical analytics. This concept allows various physical quantities, such as weight, density, viscosity or temperature, to be measured using a force-based measuring system.

An easy-to-clean laboratory environment

“In a laboratory environment, workplace surfaces remain clear of apparatus and can therefore be effectively and easily cleaned, since everything except the carrier for the item to be weighed can be screened from the surroundings,” explains Georg Berner, Head of Strategic Corporate Development, Group Holding Festo and Project Coordinator for the SupraMotion concepts. “Only the weighing pan carrying the item hovers over the table top – without the danger of cross-contamination via the workplace surface or tools.” The entire weighing apparatus can be decoupled from the surroundings without vibration by means of a frame.

If the pan is not needed, it can be removed and the entire working space of the sterile workbench becomes available. This is made possible by a special characteristic of superconductors: they can hold magnets in suspension at a fixed distance when cooled to a certain temperature. The exhibit thus impressively demonstrates how a workroom and laboratory equipment, including sensors, can be coupled to each other without contact despite spatial separation.

Applications in medical technology

In addition to purely measuring and weighing, this technology offers numerous further possibilities such as analytical determination of density or viscosity, precise metering or the surveillance of reactive or biological processes. “The possibility of handling objects without contact and thus completely free of contamination is of great interest above all in medical technology. Since no friction arises, measurements are not falsified and are absolutely precise,” says Dr. Frank Jacob, Head of the LifeTech Project Unit at Festo. “The concept of the superconductive balance is now being realised in close cooperation with one of our customers as a prototype. It shows how we can construct easy-to-clean weighing devices in future and integrate them into automated systems in combination with our drive technology.”

The technology is very robust and stable in terms of both space and time: the levitation function, which is intrinsic to the material, does not require any regulation technology and remains stable over long periods, even if the power supply is interrupted.

Superconductors: materials with special characteristics

Superconductors are materials that can store the field of a permanent magnet at a defined distance below a certain temperature. With this effect, objects can be held in position and moved free of contact. The levitation gap remains stable even beyond walls. Thanks to its restoring forces, the superconductive magnetic bearing components autonomously return to their stored positions, even if one of them is temporarily removed – without the need for external regulation technology.