New polymer films are not just actuators, but also have sensory properties. Controlled by algorithms they transform into high-tech components.
They might only be made from thin silicon film, but they can squeeze down hard, deliver a powerful thrust, vibrate or hold any required position. And because they can act as sensors, they are becoming important tools in technical applications. Researchers at Saarland University are developing a new generation of polymer film-based engineering components that can be used as continuous switches, self-metering valves, motorless pumps or even as tactile aids for touchscreens. The technology needs neither rare earths nor copper, it is cheap to produce and consumes very little energy and components made using it are astonishingly light.
Polymer films as novel actuators
Equipped only with a variable electrical voltage, the researchers can not only make an ultrathin silicon film change shape – compressing it in one direction while it expands in the other, they can also get it to perform complex choreographies – from high-frequency oscillations to continuously variable flexing motions. Films with these properties have the potential to be used as novel drives and actuators. The two sides of a polymer membrane are coated with an electrically conducting layer. Films that have been treated in this way are called ‘electroactive’ and these polymer systems are known as ‘electroactive polymers’ or ‘dielectric elastomers.
If the engineers alter the applied electric field, the electrostatic attractive forces change accordingly and the film gets thinner while its area enlarges. When controlled by algorithms running in the background, this rather nondescript piece of polymer with a black coating transforms into a high-tech component that can be precisely controlled by an electric voltage.
The film itself is used as a position sensor. It is not just an actuator, but also has sensory properties. The research team can very precisely assign changes in the position of the film to changes in the film’s capacitance. By measuring the capacitance of this dielectric elastomer the researchers can infer the mechanical deformation of the film. This allows specific motion sequences to be calculated precisely and programmed in a control unit.
Highly energy-efficient components
The research team at Saarland University and at the Center for Mechatronics and Automation Technology (ZeMA) is developing the polymer films in order to produce a wide variety of engineering components. Examples include a precision self-metering valve that operates without needing to be driven by compressed air or liquids, pump drives that do not require a conventional motor, or buttons for switching things on or off. These components are highly energy-efficient and the film does not require any energy in order to maintain a specific position. It only needs energy when it changes its position. When used as a pneumatic valve, the energy efficiency is about 500 times greater than that of a conventional solenoid valve.
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