New lightweight, compact and energy-efficient pumps and valves made from elastomeric films could change the pumping industry for the better.
Miniaturised pumps and valves that rely on the motion of dielectric elastomeric silicone films are being created in Saarland, Germany. Not only are these devices lightweight, compact and energy-efficient, but they also work without the need for compressed air, motors or lubricants. They are cleanroom-compatible and can be continuously controlled while operating.
The research team led by Professors Stefan Seelecke and Paul Motzki from Saarland University will exhibit a prototype film-based vacuum pump at this year’s Hannover Messe from 31 March to 4 April. Their lightweight, low-energy technology can pull a vacuum down to 300 millibars of pressure (30 per cent of standard atmospheric pressure).
The pumps and valves developed by the research team at Saarland University and the Center for Mechatronics and Automation Technology (ZeMA) operate entirely without external motors and consume little energy. At the heart of these devices are thin silicone films that can be moved simply by applying a small electrical voltage.
Vacuum technology is ubiquitous, from the home vacuum sealers used to keep foods fresher for longer to the brake boosters used in cars. Vacuum systems are crucial in the medical field (surgical suction systems), in the pharmaceutical and biotech and foods sectors (freeze-drying, distillation, etc.) and in industrial processing (robot grippers that sort products on conveyor belts). Conventional means of creating a vacuum require using a motor-driven vacuum pump. In addition to consuming a lot of energy, these pumps are often bulky and noisy. This type of pump needs to be serviced and lubricated, which is often difficult in cleanrooms or sterile environments.
“Our technology is cost-effective to manufacture. Because the components are lightweight, we save space and weight, meaning that the pumps and valves we’re developing are much more energy-efficient than equivalent devices that use conventional technology. Compared with a commercially available pneumatic solenoid valve, i.e. one driven by an electromagnet, we can drive the same valve using 400 times less energy,” said Paul Motzki, Professor of Smart Material Systems for Innovative Production at Saarland University and Scientific Director/CEO at ZeMA gGmbH.
The Saarbrücken technology can be manufactured without expensive or hard-to-source materials like copper or rare earth elements. Another advantage is noise reduction, with film-based pumps significantly quieter than conventional compressor-driven pumps.
The silicone film itself has a thickness of only about one-twentieth of a millimetre, and the researchers can precisely control the movements of these ultrathin films. This is because a highly flexible electrically conducting layer is printed onto each side of the film to create what is known as a dielectric elastomer. If the engineers apply a voltage to the elastomer film, the conducting layers attract each other, compressing the polymer and causing it to expand sideways, thus increasing its surface area.
“We’re using these dielectric elastomers to develop novel drive systems that do not need to be equipped with additional sensors,” Motzki said.
By varying the applied electric field, the researchers can make the elastomeric film execute continuously variable flexing motions, oscillate or flex at some required frequency, or hold the film in a specific fixed position without requiring a continuous supply of energy.
“These dielectric elastomer films are self-sensing and can act as their position sensors,” said Motzki.
A precise electrical capacitance value can be assigned to each deformation or change in the position of the film. Even the slightest movement of the film results in a change in the capacitance. The engineers can precisely quantify the film’s spatial deformation using these capacitance values. By combining the capacitance data and AI-based machine learning, the team has developed a control unit that can predict and program motion sequences and thus precisely control how the elastomer film deforms. By incorporating these dielectric elastomer actuators into appropriately designed equipment, the research team can create motorless pumps that can pull a vacuum, valves that can deliver exact quantities of liquid, or components that can act as step-less switches.
The capacitance data also reveals if something is not functioning as it should, for example, if the vacuum is too small or if a foreign body is blocking the valve or pump. These film-based pumps and valves are self-sensing, meaning they can perform their own condition monitoring and report on where the problem lies. When problems arise with conventional pumps and valves in large-scale industrial plants, trouble-shooting is often more complicated.
The Saarbrücken team is exhibiting at this year’s Hannover Messe, where they will demonstrate the latest prototype of their film-based vacuum pump.
“Our technology is scalable. We can increase the pressure and volume flow by connecting our actuators and pump chambers in parallel, in series or a combination of both,” said Professor Motzki.
To help visitors to the trade fair visualise the underlying technology, the research team has built a demonstrator model in which the dielectric elastomer film creates a vacuum inside a bell jar. As the pressure in the jar falls, the visitors can observe the balloon ‘inflate’ in size – an experimental demonstration that many may remember from their school physics class. As the air is sucked out from around the balloon, the air molecules in the balloon have more space in which to expand, and the balloon grows in size – except that, in this case, it all happens without a loud compressor running in the background.
