Tag Archives: electronic

Heat-free metallic print can form electronic circuits on soft surfaces (flowers, gelatin)

Martin Thuo of Iowa State University and the Ames Laboratory can show you several remarkable photos in his collection: a curled sheet of paper with a LED display or a rose with metal traces printed on a petal. This isn’t an artistic project — Thuo is working on a new technology which allows printing conductive metallic lines on all kinds of materials, from a wall to a leaf.

This could be a game changer.

Image credits: Martin Thuo.

The technology features liquid metal (alloys of bismuth, indium, and tin) and is remarkable for multiple reasons. For starters, it’s capable of producing extremely small particles, about 10 millionths of a meter across. The resulting print is also not hot, which means you can print it on anything you want — including living things.

The printed metal acts like a quickly-solidifying weld, creating conductive, metallic lines and traces which can be used for electronic circuits.

“This work reports heat-free, ambient fabrication of metallic conductive interconnects and traces on all types of substrates,” Thuo and colleagues write in a recent study.

Through the ‘printing’ process, the metal inside flows and solidifies, creating a heat-free weld or, in this case, printing conductive, metallic lines and traces on all kinds of materials — everything from a concrete wall to a leaf.

The technology could have numerous applications. It could be used to print sensors to measure the growth and state of crops (assessing whether everything is going smoothly, or if they require more water or are being attacked by pests). Similarly, the sensors could be used to monitor the structural integrity of a building. The technology has also been tested in this regard. The researchers used a paper-based setting as a base for the sensor, and the sensor read changes in electrical currents when the paper was curved. Researchers say that, ultimately, the approach could also be used for medical sensors or models for biological tissues (since it can also be printed on soft surfaces such as gelatin). All this is done without damaging the base, even when it’s a living biological system.

Printed electronic traces on gelatin. Image credits: Martin Thuo / Iowa State University.

Initially, this started as a teaching exercise. Thuo wanted to give his undergrad students something to work on that would be both useful and fun.

“I started this with undergraduate students,” he said. “I thought it would be fun to get students to make something like this. It’s a really beneficial teaching tool because you don’t need to solve 2 million equations to do sophisticated science.”

Now it’s grown spectacularly — the university has even sponsored Thuo’s lab with start-up funds to continue working on the technology.

“The students discovered ways of dealing with metal and that blossomed into a million ideas,” Thuo said. “And now we can’t stop.”

The study was published in the journal Advanced Functional Materials.

UCLA engineers develop a stretchable, foldable transparent electronic display

Take a moment to imagine a phone display as clear as a window, a curtain that can illuminate a room, and a smart phone that can stretch like rubber; now imagine all these things are made from the same material.

oled bending

Researchers from UCLA’s Henry Samueli School of Engineering and Applied Science have developed a transparent, elastic organic light-emitting device, or OLED, which has the potential to make this happen. The OLED can be repeatedly stretched, folded and twisted, all at room temperature, without anything special, while still remaining turned on and retaining its original size and shape.

OLED technology itself is not a really new idea – it’s currently used for many smartphones and some televisions. But this new, smart OLED version from UCLA could lead to foldable and expandable screens for new classes of smartphones, as well as electronic-integrated clothing, wallpaper lighting, new minimally invasive medical tools, and many, many others.

“Our new material is the building block for fully stretchable electronics for consumer devices,” said Qibing Pei, a UCLA professor of materials science and engineering and principal investigator on the research. “Along with the development of stretchable thin-film transistors, we believe that fully stretchable interactive OLED displays that are as thin as wallpaper will be achieved in the near future. And this will give creative electronics designers new dimensions to exploit.”

In order to test their results, researchers stretched and restretched the OLED 1,000 times, extending it up to 30 percent its original size – and it still continued to work at very high efficiency. If you cut back on some efficiency, you can stretch it to double its initial size, while also folding it 180 degrees and twisting it in multiple directions. It’s also fairly easy and cheap to produce.

“The lack of suitable elastic transparent electrodes is one of the major obstacles to the fabrication of stretchable display,” Liang said. “Our new transparent, elastic composite electrode has high visual transparency, good surface electrical conductivity, high stretchability and high surface smoothness — all features essential to the fabrication of the stretchable OLED.”


They also demonstrated that such an OLED technology could feature multiple pixels, rather than just a solid block of light.

“While we perceive a bright future where information and lighting are provided in various thin, stretchable or conformable form factors, or are invisible when not needed, there are still major technical challenges,” Pei said. “This includes how to seal these materials that are otherwise sensitive to air. Researchers around the world are racing the clock tackling the obstacles. We are confident that we will get there and introduce a number of cool products along the way.”

The results were published in Nature Photonics.