Mirroring the process of additive manufacturing, engineers from the University of California San Diego (UCSD) have created a 3D stretchable electronic device, dubbed as the “smart bandage”, that wirelessly monitors human body signals such as eye movement, temperature, and heart and brain activity.
By fashioning elastomer films on top of each other, the smart bandage, which is the same size and width of a U.S. dollar coin, is able to accommodate more circuitry for a variety of functions.
“Our vision is to make 3D stretchable electronics that are as multifunctional and high-performing as today’s rigid electronics,” said Sheng Xu, a Professor in the Department of NanoEngineering and the Center for Wearable Sensors, both at the UCSD Jacobs School of Engineering.
3D stretchable electronics
According to the UCSD research paper, stretchable electronics, an emerging technology, create devices with the ability to conform to dynamic surfaces such as the human body.
Standard stretchable configurations are limited to single-layer designs due to the lack of material processing capabilities in soft electronic systems. Therefore, the Xu Research Group, inspired by the process of additive manufacturing, built a four-layer silicone elastomer substrate 3D integrated stretchable electronic device. Professor Xu stated:
“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.”
Each layer is patterned with an “island-bridge”, a small, rigid electronic connecting component including sensors, antennas, a Bluetooth chip, an amplifier, an accelerometer, a resistor, a capacitor, and an inductor.
The islands-bridges are supported by thin, spring-shaped copper wires, which allows flexibility within the circuits while maintaining electronic function. To create the smart bandage, the Xu Research Group used 3D microfabrication which uses laser beam soldering on elastomeric substrates to create electrical connections between layers – vertical interconnect accesses (VIA).
The multi-purpose 3D smart bandage
The smart bandage sticks onto various parts of the human body to monitor different electrical signals. When worn on the chest or stomach, the bandage records heart signals – much like an electrocardiogram (ECG) machine.
On the forehead, it records brain signals, mimicking the functions of an electroencephalography (EEG) sensor, and when placed on the side of the head, it records eyeball movements. Placing the smart bandage on the forearm will record muscle activity and can also be used to remotely control a robotic arm.
“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 Zhenlong Huang, co-author and visiting Ph.D. student in the Xu Research Group.
3D printing and dynamic surfaces
Similar to the smart bandage, UCSD researchers have previously used 3D printing methods to conquer dynamic, non-planar (asymmetrical) surfaces, outside of the human body.
Last year, UCSD bioengineers presented a research paper demonstrating a robot capable of walking over uneven surfaces as a result of 3D printed leg actuators.
Following this, UCSD researchers used nanoscale 3D printing on dynamic surfaces to replicate the radiant color patterns distributed by male Peacock Spiders.
The research paper “Three-dimensional integrated stretchable electronics” is co-authored by the Xu Research Group.
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Featured image shows the 3D smart bandage. Photo via UCSD.
