Researchers have been working tirelessly in recent years to come up with smaller and flexible sensors for myriad Internet of Things (IoT) devices. Such devices are beginning to flood the market on their way to becoming ubiquitous throughout businesses, people’s homes, and even public locations. A team at Purdue University and the University of Virginia has come up with a solution in the development of electronic stickers that could allow these devices to sense their environment and eventually connect with other devices.
The stickers were created using a new fabrication method invented by a team led by Chi Hwan Lee, Purdue assistant professor of biomedical engineering and mechanical engineering. The method uses something called “transfer printing” to make tiny, thin-film electronic circuits that can be peeled from a surface.
This process eliminates several manufacturing steps and their associated costs. It also can turn any object essentially into a “smart object” that can sense its environment or be controlled through the application of a high-tech sticker, Lee told Design News.
“I thought that it would be great to have sticker-like thin-film sensors, such that it can be easily pasted onto any place of interest,” he said. Indeed, billions of objects ranging from smartphones and watches to buildings, appliances, machine parts, and medical devices have now become wireless sensors of their environments to create an ever-expanding IoT network. “With this approach, any surface can become functional and smart,” he added.
|A thin-film electronic circuit can peel easily from its silicon wafer with water, making the wafer reusable for building a nearly infinite number of circuits. (Image source: Purdue University image/Chi Hwan Lee)|
The technology enabling these devices to communicate and sense their environment and each other will need to allow complex functionality in smaller and simpler form factors that won’t weigh down devices or drain their energy. Until now, embedding high-performance electronic functionality into an arbitrary surface or substrate has been limited because of materials and manufacturing processes, Lee said.
Most of today’s electronic circuits are individually built on their own silicon “wafer,” a flat and rigid substrate that can withstand the high temperatures and chemical etching that are used to remove the circuits from the wafer. However, that process damages the silicon wafer, forcing the manufacturing process to accommodate an entirely new wafer each time. The sticker-like thin-film sensor technology can overcome this challenge by streamlining and simplifying the process considerably, Lee said. “Uniquely, this transfer-printing approach utilizes a controlled interfacial de-bonding process in a water environment at room temperature that allows clean, intact delamination of pre-fabricated thin-film devices from the original wafer,” Lee explained.
This is far simpler than conventional transfer-printing methods for electronic materials, he noted. “Using mechanical peeling in water rather than soaking in an etching solution for a long time can provide benefits in the manufacturing scheme in terms of simplicity, controllability, and cost-effectiveness.”
Lee said the sticker system can include various kinds of thin-film sensors that are incorporated with nanoscale semiconducting materials, such as silicon nanomembranes, nanoribbons, and nanowires—all of which are adhered on the surface of a thermally releasable tape. “The sticker can serve as a temporary holder in which you can easily handle and paste the electronics onto the surface where you want them to be, and then you can easily remove the sticker from the surface, leaving the electronics behind,” he explained.
Researchers experimented with the use of stickers—placing one, for example, on a flower pot, which made the pot capable of sensing temperature changes that could affect the plant’s growth. “Any objects can become smart and functional in this scheme…to detect environmental parameters, such as temperature and light, and/or provide electronic features, such as switches to operate LEDs, etc.,” Lee explained.
The team envisions that their technology even can be attached onto the service of unmanned aerial vehicles (UAVs) to monitor environmental gases or other conditions during flight. Researchers plan to continue their work to improve the technology, Lee said. Specifically, the team aims to overcome challenges associated with integrating the stickers with thin-film renewable-energy sources, such as solar cells and other energy harvesters—essentially to create a self-sustainable sensor system for myriad IoT devices, Lee said.
Elizabeth Montalbano is a freelance writer who has written about technology and culture for 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco, and New York City. In her free time, she enjoys surfing, traveling, music, yoga, and cooking. She currently resides in a village on the southwest coast of Portugal.
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