By stacking and connecting layers of stretchable circuits on top of one another, engineers have developed an approach to build soft, pliable "3D stretchable electronics" that can pack a lot of functions while staying thin and small in size. The work is published in the Aug. 13 issue of Nature Electronics.
As a proof of concept, a team led by the University of California San Diego has built a stretchable electronic patch that can be worn on the skin like a bandage and used to wirelessly monitor a variety of physical and electrical signals, from respiration, to body motion, to temperature, to eye movement, to heart and brain activity. The device, which is as small and thick as a U.S. dollar coin, can also be used to wirelessly control a robotic arm.
"Our vision is to make 3D stretchable electronics that are as multifunctional and high-performing as today's rigid electronics," said senior author Sheng Xu, a professor in the Department of NanoEngineering and the Center for Wearable Sensors, both at the UC San Diego Jacobs School of Engineering.
Xu was named among MIT Technology Review's 35 Innovators Under 35 list in 2018 for his work in this area.
To take stretchable electronics to the next level, Xu and his colleagues are building upwards rather than outwards. "Rigid electronics can offer a lot of functionality on a small footprint--they can easily be manufactured with as many as 50 layers of circuits that are all intricately connected, with a lot of chips and components packed densely inside. Our goal is to achieve that with stretchable electronics," said Xu.
The new device developed in this study consists of four layers of interconnected stretchable, flexible circuit boards. Each layer is built on a silicone elastomer substrate patterned with what's called an "island-bridge" design.
Each "island" is a small, rigid electronic part (sensor, antenna, Bluetooth chip, amplifier, accelerometer, resistor, capacitor, inductor, etc.) that's attached to the elastomer. The islands are connected by stretchy "bridges" made of thin, spring-shaped copper wires, allowing the circuits to stretch, bend and twist without compromising electronic function.
This work overcomes a technological roadblock to building stretchable electronics in 3D. "The problem isn't stacking the layers. It's creating electrical connections between them so they can communicate with each other," said Xu. These electrical connections, known as vertical interconnect accesses or VIAs, are essentially small conductive holes that go through different layers on a circuit. VIAs are traditionally made using lithography and etching. While these methods work fine on rigid electronic substrates, they don't work on stretchable elastomers.
So Xu and his colleagues turned to lasers. They first mixed silicone elastomer with a black organic dye so that it could absorb energy from a laser beam. Then they fashioned circuits onto each layer of elastomer, stacked them, and then hit certain spots with a laser beam to create the VIAs. Afterward, the researchers filled in the VIAs with conductive materials to electrically connect the layers to one another. And a benefit of using lasers, notes Xu, is that they are widely used in industry, so the barrier to transfer this technology is low.
Multifunctional 'smart bandage'
The team built a proof-of-concept 3D stretchable electronic device, which they've dubbed a "smart bandage." A user can stick it on different parts of the body to wirelessly monitor different electrical signals. When worn on the chest or stomach, it records heart signals like an electrocardiogram (ECG). On the forehead, it records brain signals like a mini EEG sensor, and when placed on the side of the head, it records eyeball movements. When worn on the forearm, it records muscle activity and can also be used to remotely control a robotic arm. The smart bandage also monitors respiration, skin temperature and body motion.
"We didn't have a specific end use for all these functions combined together, but the point is that we can integrate all these different sensing capabilities on the same small bandage," said co-first author Zhenlong Huang, who conducted this work as a visiting Ph.D. student in Xu's research group.
And the researchers did not sacrifice quality for quantity. "This device is like a 'master of all trades.' We picked high quality, robust subcomponents--the best strain sensor we could find on the market, the most sensitive accelerometer, the most reliable ECG sensor, high quality Bluetooth, etc.--and developed a clever way to integrate all these into one stretchable device," added co-first author Yang Li, a nanoengineering graduate student at UC San Diego in Xu's research group.
So far, the smart bandage can last for more than six months without any drop in performance, stretchability or flexibility. It can communicate wirelessly with a smartphone or laptop up to 10 meters away. The device runs on a total of about 35.6 milliwatts, which is equivalent to the power from 7 laser pointers.
The team will be working with industrial partners to optimize and refine this technology. They hope to test it in clinical settings in the future.
Paper title: "Three-Dimensional Integrated Stretchable Electronics." Co-authors include joint co-first authors Zhenlong Huang, Yifei Hao and Yang Li, Hongjie Hu, Chonghe Wang, Akihiro Nomoto, Yue Gu, Yimu Chen, Tianjiao Zhang, Weixin Li, Yusheng Lei, NamHeon Kim, Chunfeng Wang, Lin Zhang, Ayden Maralani, Xiaoshi Li and Albert Pisano, UC San Diego; Taisong Pan and Yuan Lin, University of Electronic Science and Technology of China; Jeremy W. Ward and Michael F. Durstock, The Air Force Research Laboratory, Wright-Patterson Air Force Base.
This work is supported by the Center for Wearable Sensors, Center of Healthy Aging and the Contextual Robotics Institute, all at UC San Diego, and the National Institutes of Health (grant UL1TR001442).
Ioana Patringenaru | EurekAlert!
Scientists use artificial neural networks to predict new stable materials
18.09.2018 | University of California - San Diego
ORNL-developed technology streamlines computational science projects
17.09.2018 | DOE/Oak Ridge National Laboratory
Thin-film solar cells made of crystalline silicon are inexpensive and achieve efficiencies of a good 14 percent. However, they could do even better if their shiny surfaces reflected less light. A team led by Prof. Christiane Becker from the Helmholtz-Zentrum Berlin (HZB) has now patented a sophisticated new solution to this problem.
"It is not enough simply to bring more light into the cell," says Christiane Becker. Such surface structures can even ultimately reduce the efficiency by...
A study in the journal Bulletin of Marine Science describes a new, blood-red species of octocoral found in Panama. The species in the genus Thesea was discovered in the threatened low-light reef environment on Hannibal Bank, 60 kilometers off mainland Pacific Panama, by researchers at the Smithsonian Tropical Research Institute in Panama (STRI) and the Centro de Investigación en Ciencias del Mar y Limnología (CIMAR) at the University of Costa Rica.
Scientists established the new species, Thesea dalioi, by comparing its physical traits, such as branch thickness and the bright red colony color, with the...
Scientists have succeeded in observing the first long-distance transfer of information in a magnetic group of materials known as antiferromagnets.
An international team of researchers has mapped Nemo's genome, providing the research community with an invaluable resource to decode the response of fish to...
Graphene is considered a promising candidate for the nanoelectronics of the future. In theory, it should allow clock rates up to a thousand times faster than today’s silicon-based electronics. Scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) and the University of Duisburg-Essen (UDE), in cooperation with the Max Planck Institute for Polymer Research (MPI-P), have now shown for the first time that graphene can actually convert electronic signals with frequencies in the gigahertz range – which correspond to today’s clock rates – extremely efficiently into signals with several times higher frequency. The researchers present their results in the scientific journal “Nature”.
Graphene – an ultrathin material consisting of a single layer of interlinked carbon atoms – is considered a promising candidate for the nanoelectronics of the...
03.09.2018 | Event News
27.08.2018 | Event News
17.08.2018 | Event News
18.09.2018 | Materials Sciences
18.09.2018 | Materials Sciences
18.09.2018 | Information Technology