Nov. 18 - Researchers at Harvard University have developed a transparent stretchable hydrogel to conduct electricity to flexible devices like medical implants or wearable computers. As a proof of concept, the scientists have turned their hydrogel into a loudpseaker, so the curious can hear all about it. Ben Gruber reports.
The video comes from YouTube, but the audio in this case, is made possible by the transparent circular object in front of the screen. It's an ionic speaker that's the first of its kind. It's made of a thin piece of rubber sandwiched between layers of hydrogel, a synthetic, jelly-like substance with conductive properties. Researcher Christoph Keplinger says that when an electrical charge is applied, the rubber in the middle expands and contracts. (SOUNDBITE) (English) CHRISTOPH KEPLINGER, RESEARCHER, HARVARD UNIVERSITY, SAYING: "So we switch on the voltage it deforms, we switch off, it goes back to the original shape because the rubber stores the elastic energy and if we do that many times in a second then we create vibrations and vibrations is what we hear as sound." Keplinger's colleague Jeong Yun Sun says that while the speaker attracts attention, it was built only to illustrate the capabilities and potential of the hydrogel. (SOUNDBITE) (English) JEONG-YUN SUN, RESEARCHER, HARVARD UNIVERSITY, SAYING: "What we are doing is not a loud speaker that is just one demonstration. What we are doing is making stretchable ionics." ..and the team believes stretchable ionics made from hydrogel will power devices of the future. Made by combining saltwater - which conducts electricity - with a polymer framework to give it form, the hydrogel allows electrically charged particles - or ions - to pass through it, even when it's being bent, folded or twisted. According to Keplinger, hydrogel's flexibility is its advantage over conventional conductive materials. (SOUNDBITE) (English) CHRISTOPH KEPLINGER, RESEARCHER, HARVARD UNIVERSITY, SAYING: "It all started with the problem if you think about a metal. It conducts electricity but it is not stretchable and it is not transparent. But such emerging fields such as stretchable electronics where you would interface electronic devices with your body or with other soft systems such as soft robots, actually require conductors that are stretchable." …much like their speaker. But in order to replicate the ionic system that carries electrical signals naturally through the body from the brain , the team has a great deal of work to do. Hydrogel does not last long before it degrades. Keplinger and Sun are now working to give it a longer shelf life. (SOUNDBITE) (English) JEONG-YUN SUN, RESEARCHER, HARVARD UNIVERSITY, SAYING: "The hydrogel, because it contains lots of water, actually more than 90 percent is water, and water evaporates which means we can play music for only two hours...(laughing)..that's terrible right?" It may be terrible for now, but the team sees a big future for ionic conductors in technologies that are only beginning to emerge.