Generating a real buzz

C&I Issue 4, 2012

Game consoles and mobile phones have come a long away in terms of size, high quality graphics and sound but, until recently, the same could not be said about the ‘haptics’ or tactile feedback of these devices. Whether a car hits a barrier around a race track, or a round of bullets is fired from a machine gun, or a pinball hits a bumper, the feeling you experience is the same – a vibration or buzz no different to the sensation you experience when your mobile phone alerts you to a text message.

Now, scientists at Bayer MaterialScience have taken gaming and mobile phones to a new level. By using electroactive polymers in the design of the motors or actuators used to create movement in these products, they provide the consumer with something that is as close as it gets to the real word experience. The new actuator technology, ViviTouch, also promises to bring improvements to the audio industry as well as certain medical devices.

Traditionally, motors used to create vibrations comprise electromagnets, or piezoelectric materials – ceramics that under pressure produce electricity which drives a motor. But these are comparatively cumbersome and inefficient and always produce the same degree of vibration. In the late 1990s, researchers at SRI International (formerly Stanford Research Institute) in California, US realised that to take robotic technology on to the next level and emulate ‘muscle movement’, they would need more efficient, lightweight motors, and came up with the idea of using electroactive polymers.

Within five years, and after a string of patents and publications, Artificial Muscle (AM) was born as a spin-out company from SRI International to exploit these materials. Dirk Schapeler, ceo of AM, says: ‘We evaluated many different applications for our actuator technology – pumps and valves for automotive and medical applications, optical positioners for cell phone and digital cameras, but we decided to focus initially on the gaming applications because we realised that the high definition “feel” we could achieve with our technology would provide us with a large market opportunity.’

During these early days AM scientists worked collaboratively with Bayer MaterialScience on the polymer formulations. In 2008, Bayer MaterialScience created a functional films division and acquired AM as part of its business strategy.

The new technology, which has just hit the high street as an accessory manufactured by designers Mophie for the iPod touch, exploits the electrostatic force that results when a voltage is applied across electroactive polymers (EAPs). The polymer deforms and expands, providing motion. ‘In electromagnetic motors you have to wait for the rotor to spin, and it only spins at one speed and so you always get the same buzz,’ explains Schapeler. ‘Electroactive polymers act like a capacitor; as you change the voltage it moves and is capable of responding at the speed of sound, so it is incredibly fast. The power used is about a third of that used by conventional motors and they operate in almost silence. It can follow any analogue wave function and so some very complex effects can be generated. We can create literally any tactile sensation – from a ball rolling on a surface, through the different vibrations you get from different strings on a guitar, to the feeling you get when you dial a number on an old fashioned dial phone.’

The motor is manufactured in any shape or size by using conventional screen printing, and comprises conductive polymer electrodes on the top and bottom side of a thin (25μm) dielectric EAP film, held together by a structural material 5x5x 0.5mm. The EAP is silicone. The Bayer researchers are currently trying to develop systems that won’t need a frame and simply use adhesives to hold the various components in place. This will extend the use of these motors to mobile phone and tablet applications where the focus is on ever thinner products.

For the future, the researchers are  looking to replace silicone with the ubiquitous polyurethanes, which will open up myriad applications, especially in consumer electronics.

Thumbs up – new game controller feels good

Mechanical engineers at the University of Utah, US, have designed a ‘skin-stretch’ device that looks like a pencil rubber and fits on the top of a game controller’s normal thumb joysticks. The researchers say the device, which is made from a common thermoplastic, pulls and stretches the thumb tips in different directions to give the player a more realistic experience of, for example, the tug of a fishing line or the recoil from a gun.

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