Team's flexible micro LEDs may reshape future of wearable technology
Novel devices can be folded, cut, attached to surfaces

Date:
August 31, 2020
Source:
University of Texas at Dallas
Summary:
Researchers have developed a method to create micro LEDs that can
be folded, twisted, cut and stuck to different surfaces.



FULL STORY ========================================================================== University of Texas at Dallas researchers and their international
colleagues have developed a method to create micro LEDs that can be
folded, twisted, cut and stuck to different surfaces.


==========================================================================
The research, published online in June in the journal Science Advances,
helps pave the way for the next generation of flexible, wearable
technology.

Used in products ranging from brake lights to billboards, LEDs are ideal components for backlighting and displays in electronic devices because
they are lightweight, thin, energy efficient and visible in different
types of lighting.

Micro LEDs, which can be as small as 2 micrometers and bundled to be any
size, provide higher resolution than other LEDs. Their size makes them a
good fit for small devices such as smart watches, but they can be bundled
to work in flat- screen TVs and other larger displays. LEDs of all sizes, however, are brittle and typically can only be used on flat surfaces.

The researchers' new micro LEDs aim to fill a demand for bendable,
wearable electronics.

"The biggest benefit of this research is that we have created a detachable
LED that can be attached to almost anything," said Dr. Moon Kim, Louis
Beecherl Jr.

Distinguished Professor of materials science and engineering at UT Dallas
and a corresponding author of the study. "You can transfer it onto your clothing or even rubber -- that was the main idea. It can survive even
if you wrinkle it.

If you cut it, you can use half of the LED." Researchers in the Erik
Jonsson School of Engineering and Computer Science and the School of
Natural Sciences and Mathematics helped develop the flexible LED through
a technique called remote epitaxy, which involves growing a thin layer
of LED crystals on the surface of a sapphire crystal wafer, or substrate.



========================================================================== Typically, the LED would remain on the wafer. To make it detachable, researchers added a nonstick layer to the substrate, which acts similarly
to the way parchment paper protects a baking sheet and allows for
the easy removal of cookies, for instance. The added layer, made of a one-atom-thick sheet of carbon called graphene, prevents the new layer
of LED crystals from sticking to the wafer.

"The graphene does not form chemical bonds with the LED material, so it
adds a layer that allows us to peel the LEDs from the wafer and stick
them to any surface," said Kim, who oversaw the physical analysis of the
LEDs using an atomic resolution scanning/transmission electron microscope
at UT Dallas' Nano Characterization Facility.

Colleagues in South Korea carried out laboratory tests of LEDs by adhering
them to curved surfaces, as well as to materials that were subsequently twisted, bent and crumpled. In another demonstration, they adhered an
LED to the legs of a Lego minifigure with different leg positions.

Bending and cutting do not affect the quality or electronic properties
of the LED, Kim said.

The bendy LEDs have a variety of possible uses, including flexible
lighting, clothing and wearable biomedical devices. From a manufacturing perspective, the fabrication technique offers another advantage: Because
the LED can be removed without breaking the underlying wafer substrate,
the wafer can be used repeatedly.

"You can use one substrate many times, and it will have the same functionality," Kim said.

In ongoing studies, the researchers also are applying the fabrication
technique to other types of materials.

"It's very exciting; this method is not limited to one type of material,"
Kim said. "It's open to all kinds of materials."

========================================================================== Story Source: Materials provided by
University_of_Texas_at_Dallas. Original written by Kim Horner. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Junseok Jeong, Qingxiao Wang, Janghwan Cha, Dae Kwon Jin, Dong
Hoon Shin,
Sunah Kwon, Bong Kyun Kang, Jun Hyuk Jang, Woo Seok Yang, Yong
Seok Choi, Jinkyoung Yoo, Jong Kyu Kim, Chul-Ho Lee, Sang Wook Lee,
Anvar Zakhidov, Suklyun Hong, Moon J. Kim, Young Joon Hong. Remote
heteroepitaxy of GaN microrod heterostructures for deformable
light-emitting diodes and wafer recycle. Science Advances, 2020;
6 (23): eaaz5180 DOI: 10.1126/ sciadv.aaz5180 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200831112314.htm

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