'Soft machines' to power new-age robots

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.

"However, new manufacturing techniques must be developed before soft machines become commercially practical," said Rebecca Kramer, 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.

The researchers embedded liquid-alloy devices into a rubber-like polymer called polydimethylsiloxane (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.

"We exploit its 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.

The new process also can be used to fabricate pressure sensors, capacitors and conductors.

"While this is a huge step forward, we need to continue to decrease scale and increase density to develop sensors and electronics that are comparable to traditional, rigid devices and that mimic the functionality of human skin," Kramer added.

The findings appeared in the journal Advanced Functional Materials.