Engineers mix and match materials to make new stretchy electronics

IMAGE: With a new method, MIT scientists can peel and stack thin movies of metal oxides — chemical substances that can be developed to have distinct magnetic and electronic homes. The…
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Credit: Image: Felice Frankel

At the heart of any electronic gadget is a cold, tough computer system chip, covered in a mini city of transistors and other semiconducting aspects. Since computer system chips are stiff, the electronic gadgets that they power, such as our mobile phones, laptop computers, watches, and tvs, are likewise inflexible.

Now a procedure established by MIT engineers might be the secret to production versatile electronics with numerous performances in an affordable method.

The procedure is called “remote epitaxy” and includes growing thin movies of semiconducting product on a big, thick wafer of the very same product, which is covered in an intermediate layer of graphene. When the scientists grow a semiconducting movie, they can peel it far from the graphene-covered wafer and then recycle the wafer, which itself can be costly depending upon the kind of product it’s made from. In this method, the group can copy and peel away any variety of thin, versatile semiconducting movies, utilizing the very same underlying wafer.

In a paper released in the journal Nature, the scientists show that they can utilize remote epitaxy to produce freestanding movies of any practical product. More significantly, they can stack movies made from these various materials, to produce versatile, multifunctional electronic gadgets.

The scientists anticipate that the procedure might be utilized to produce stretchy electronic movies for a wide array of usages, consisting of virtual reality-made it possible for contact lenses, solar-powered skins that mold to the shapes of your automobile, electronic materials that react to the weather condition, and other versatile electronics that appeared previously to be the things of Marvel films.

“You can use this technique to mix and match any semiconducting material to have new device functionality, in one flexible chip,” states Jeehwan Kim, an associate teacher of mechanical engineering at MIT. “You can make electronics in any shape.”

Kim’s co-authors consist of Hyun S. Kum, Sungkyu Kim, Wei Kong, Kuan Qiao, Peng Chen, Jaewoo Shim, Sang-Hoon Bae, Chanyeol Choi, Luigi Ranno, Seungju Seo, Sangho Lee, Jackson Bauer, and Caroline Ross from MIT, together with partners from the Uniersity of Wisconsin at Madison, Cornell University, the University of Virginia, Penn State University, Sun Yat-Sen University, and the Korea Atomic Energy Research Institute.

Buying time

Kim and his associates reported their very first outcomes utilizing remote epitaxy in 2017. Then, they were able to produce thin, versatile movies of semiconducting product by very first positioning a layer of graphene on a thick, costly wafer made from a mix of unique metals. They streamed atoms of each metal over the graphene-covered wafer and discovered the atoms formed a movie on top of the graphene, in the very same crystal pattern as the underlying wafer. The graphene supplied a nonstick surface area from which the scientists might peel away the new movie, leaving the graphene-covered wafer, which they might recycle.

In 2018, the group revealed that they might utilize remote epitaxy to make semiconducting materials from metals in groups 3 and 5 of the table of elements, however not from group 4. The factor, they discovered, condensed to polarity, or the particular charges in between the atoms streaming over graphene and the atoms in the underlying wafer.

Since this awareness, Kim and his associates have actually attempted a variety of significantly unique semiconducting mixes. As reported in this new paper, the group utilized remote epitaxy to make versatile semiconducting movies from intricate oxides — chemical substances made from oxygen and a minimum of 2 other aspects. Complex oxides are understood to have a large range of electrical and magnetic homes, and some mixes can produce a present when physically extended or exposed to an electromagnetic field.

Kim states the capability to manufacture versatile movies of intricate oxides might unlock to new energy-havesting gadgets, such as sheets or coverings that extend in reaction to vibrations and produce electrical energy as an outcome. Previously, intricate oxide materials have actually just been produced on stiff, millimeter-thick wafers, with minimal versatility and for that reason minimal energy-generating capacity.

The scientists did have to modify their procedure to make intricate oxide movies. They at first discovered that when they attempted to make an intricate oxide such as strontium titanate (a substance of strontium, titanium, and 3 oxygen atoms), the oxygen atoms that they streamed over the graphene tended to bind with the graphene’s carbon atoms, engraving away littles graphene rather of following the underlying wafer’s pattern and binding with strontium and titanium. As a remarkably basic repair, the scientists included a 2nd layer of graphene.

“We saw that by the time the first layer of graphene is etched off, oxide compounds have already formed, so elemental oxygen, once it forms these desired compounds, does not interact as heavily with graphene,” Kim describes. “So two layers of graphene buys some time for this compound to form.”

Peel and stack

The group utilized their freshly fine-tuned procedure to make movies from numerous complex oxide materials, peeling each 100-nanometer-thin layer as it was made. They were likewise able to stack together layers of various complex oxide materials and successfully glue them together by warming them a little, producing a versatile, multifunctional gadget.

“This is the first demonstration of stacking multiple nanometers-thin membranes like LEGO blocks, which has been impossible because all functional electronic materials exist in a thick wafer form,” Kim states.

In one experiment, the group stacked together movies of 2 various complex oxides: cobalt ferrite, understood to broaden in the existence of an electromagnetic field, and PMN-PT, a product that produces voltage when extended. When the scientists exposed the multilayer movie to an electromagnetic field, the 2 layers interacted to both broaden and produce a little electrical existing.

The outcomes show that remote epitaxy can be utilized to make versatile electronics from a mix of materials with various performances, which formerly were tough to integrate into one gadget. When it comes to cobalt ferrite and PMN-PT, each product has a various crystalline pattern. Kim states that conventional epitaxy strategies, which grow materials at heats on one wafer, can just integrate materials if their crystalline patterns match. He states that with remote epitaxy, scientists can make any variety of various movies, utilizing various, recyclable wafers, and then stack them together, despite their crystalline pattern.

“The big picture of this work is, you can combine totally different materials in one place together,” Kim states. “Now you can imagine a thin, flexible device made from layers that include a sensor, computing system, a battery, a solar cell, so you could have a flexible, self-powering, internet-of-things stacked chip.”

The group is checking out different mixes of semiconducting movies and is dealing with establishing model gadgets, such as something Kim is calling an “electronic tattoo” — a versatile, transparent chip that can connect and adhere to an individual’s body to sense and wirelessly relay crucial indications such as temperature level and pulse.

“We can now make thin, flexible, wearable electronics with the highest functionality,” Kim states. “Just peel off and stack up.”


This research study was supported, in part, by the U.S. Defense Advanced Research Projects Agency.

Additional background

“Heterogenous integration of single-crystalline complex-oxide membranes.”


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