Water vapor plasma connection for ultra-thin and flexible electronics


Scientists at the RIKEN research institute in Japan have developed a new method for joining gold electrodes together within flexible electronics. The technique, which does not require stickers or high temperatures that could damage delicate electronic components, allows for extremely thin and flexible electronics and could lead to new types of medical laptops. The equipment method is based on exposing small gold electrodes to water vapor plasma before joining them. Plasma generates hydroxyl groups that help bind gold surfaces together, and the process can take place at room temperature.

Conformity test on a curved surface (radius: 0.5 mm). Ultra-thin films are bonded using the water-assisted plasma (top) or standard adhesive (bottom) bond.

Wearables offer huge opportunities for medical care, with continuous health monitoring that allows doctors to monitor their patients’ conditions over time to detect adverse events before they cause long-term complications. However, many forms of monitoring require skin contact, and this often means that the electrical components of a portable device must be flexible and thin, but also robust enough to withstand repeated movements.

One of the problems is to connect small electrodes inside the flexible thin films that form the basis of many wearables. Conventional methods, which typically require stickers or high temperatures, can damage delicate electronic components or impair the flexibility of the laptop.

To solve this, these researchers have used a softer technique, although they stumbled upon it by chance. His method is to connect gold electrodes to an ultrafine polymer sheet and then expose them to water vapor plasma for 40 seconds. The researchers then press the polymer sheets together so that the electrodes touch the areas where they are to join. After 12 hours, the electrodes come together and the flexible film can be used as desired.

“This is the first demonstration of ultra-thin, flexible gold electronics made without any adhesive,” said Kenjiro Fukuda, a researcher involved in the study. “Using this new direct link technology, we were able to manufacture an integrated system of flexible organic solar cells and organic LEDs.”

(A) Evaporated gold surfaces on 2 μm thick parile substrates were exposed to water vapor plasma. (B) The bonding of gold vapor treated with water vapor was achieved by superimposing the two substrates and storing them in ambient air for a few seconds to several hours without pressure or heat applied.

So far, Japanese researchers have created thin films that contain a variety of electrical components, including LEDs, and put them through the strainer by turning them around a stick and wrinkling them, without fail. .

“We hope that this new method will become a flexible wiring and assembly technology for next-generation portable electronics that can be connected to clothing and leather,” Fukuda said. “The next step is to develop this technology for use with cheaper metals, such as copper or aluminum.”

Watch one of the movies in the video below.

Study a Advances in Science: Direct gold link for flexible integrated electronics

Flashbacks: Washable and flexible batteries for portable medical devices; Flexible transistors for implantable and worn-out medical devices in the body; Printing of flexible custom electronics directly on the skin, bandages and medical devices; Hydrogels with flexible electronics herald new medical possibilities


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