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 New manufacturing methods needed for 'soft' machines, robots

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Date posted: 19/06/2014

Researchers have developed a technique that might be used to produce "soft machines" made of elastic materials and liquid metals for potential applications in robotics, medical devices and consumer electronics.

Such an elastic technology could make possible robots that have sensory skin and stretchable garments that people might wear to interact with computers or for therapeutic purposes.

However, new manufacturing techniques must be developed before soft machines become commercially practical, said Rebecca Kramer, an assistant professor of mechanical engineering at Purdue University.

She and her students are working to develop the fabrication technique, which uses a custom-built 3D printer. Recent findings show how to use the technique to create devices called strain gauges, which are commonly found in many commercial applications to measure how much something is stretching.

The findings are detailed in a research paper appearing this week in the journal Advanced Functional Materials and is featured on the journal's inside front cover. The paper was authored by postdoctoral research associate J. William Boley; doctoral student Edward L. White; George T.C. Chiu, a professor of mechanical engineering; and Kramer.

The researchers embedded liquid-alloy devices into a rubber-like polymer called polydimethylsiloxane, or PDMS, a silicon-based "elastomer." The liquid gallium-indium alloy was used to create patterns of lines to form a network of sensors.

"It has some odd properties," Kramer said. "Gallium oxidizes really quickly and forms a thick gallium-oxide skin, which is challenging to work with using typical liquid-processing techniques."

However, the Purdue researchers have invented a method that takes advantage of the alloy's oxidized skin.

"We exploit this oxide skin by using it for structural stability. This means you can print liquid on a surface and it will maintain stable structures without moving around," she said. "Once you print it you can flip it over or turn it on its side, because the liquid is encased by this oxide skin. We use this finding to embed our electronics in elastomer without ruining or altering the printed structures during the processing steps."

Strain gauges measure how much a material stretches or deforms. Because conventional strain gauges are made of rigid metal film, they can't measure more than a 1-percent deformation before breaking, whereas a soft strain gauge could continue stretching with the material, measuring 100 percent of a material's strain.

"What's exciting about the soft strain gauge is that it can detect very high strains and can deform with almost any material," Kramer said. "The skin around your joints undergoes about 50 percent strain when you bend a limb, so if you wanted to have sensory skin and wearable technology that tracks your movement you need to employ soft, stretchable materials that won't restrict your natural range of motion."

Findings in the research paper describe how to use the 3D printer to create soft strain gauges.

See the full Story via external site: www.purdue.edu



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