KAUST develops a screen printing approach for foldable electronics

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KAUST researchers have developed a screen-printing approach to creating bendable circuitry that could make many devices easier and cheaper to mass-produce.

A composite ink composed of ceramic particles dispersed in a polymer could make bendable electronics easier and cheaper to manufacture on an industrial scale. Image credit: 2021 KAUST; Hassan Tahini

The researchers developed the method combining composite and metallic screen-printable inks. The devices can be mounted on a variety of mediums, including non-flat surfaces, and the team believes they could enable many IoT (Internet of Things) applications.

Next-generation technologies such as automotive radars for self-driving cars, smart buildings, and wearable sensors will rely more on the high-frequency millimeter wave band, including 5G.

To date, large-scale manufacturing approaches for fabricating bendable electronics have focused on developing metallic inks and printing conductive patterns and neglected dielectric substrates.

Barriers to the use of substrates such as paper and some polymeric films in bendable electronics include cumbersome and complex manufacturing processes that cannot produce flexible multi-layered or ultra-thin devices. These substrates also have a dielectric loss that exceeds the requirements of millimeter wave devices.

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Led by Atif Shamim, the KAUST team now claims to have developed a composite ink composed of ceramic particles dispersed in acrylonitrile-butadiene-styrene (ABS) polymer.

According to the researchers, they used the new ink to generate “extremely flexible” large-area dielectric substrates with tunable lateral dimensions, thickness and permittivity. They screen-printed the ink onto glass and, after drying, peeled the substrates off the backing.

The substrates exhibited a minimum thickness of a few microns that could be increased by successive printing passes, the team said, as well as low dielectric loss at 28 GHz.

After screen-printing a silver nanowire-based ink on the dielectric substrates to create conductive patterns, the researchers found that the patterned films maintained high and stable electrical performance when rolled up or folded in half, thanks to the polymer binder present in the ink.

Moreover, they retained their performance when incorporated into a four-layer circuit composed of alternating metallic and dielectric patterned layers. This suggests that screen-printable inks can be used in multilayer structures such as printed circuit boards and automotive radar.

For proof of concept, the team screen-printed a flexible quasi-Yagi antenna onto a dielectric substrate to show that the device performed well in the millimeter wave band when bent or bent.

“Our approach will benefit new 5G antennas and accelerate 5G implementation,” said KAUST post-doctoral fellow Weiwei Li.

The team is currently exploring potential applications of the approach to other electronic devices. Li said both inks are compatible with roll-to-roll processing, which could help meet the demand for low-cost portable sensors. According to Shamim, manufacturing costs will be “extremely low” to the point that the devices will become disposable.

Their article is published in Advanced materials technologies.

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