Image: Purdue University Image / Chi Hwan Lee
Billions of objects range from smartphones and watches up to Buildings, machine parts and medical devices have become wireless sensors in their environment and expand a network called the Internet of Things.
Society tries to connect all objects to the Internet ̵
Researchers at Purdue University and the University of Virginia have developed a new manufacturing method that makes tiny thin-film circuits peel off from a surface. The technique not only eliminates multiple manufacturing steps and the associated costs, but also allows each object to perceive its environment or be controlled by the application of a high-tech sticker.
Finally, these stickers could also facilitate wireless communication. The researchers demonstrate abilities to different objects in a recent work published in the Proceedings of the National Academy of Sciences . A YouTube video is available.
"We could adapt a sensor, stick it on a drone and send the drone to dangerous areas to detect gas leaks, for example," said Chi Hwan Lee, Purdue Assistant Professor of Biomedical Engineering and Mechanical Engineering
Most of today's electronic circuits are individually on their own silicon "wafer", a flat and rigid substrate. The silicon wafer can then withstand the high temperatures and chemical etching used to remove the circuitry from the wafer.
But high temperatures and etching damage the silicon wafer and force the manufacturing process to accommodate a completely new wafer every time. Lee's new manufacturing technique called "transfer printing" lowers the manufacturing cost by using a single wafer to form a near-infinite number of thin films containing electronic circuits. Instead of high temperatures and chemicals, the film can peel off at room temperature with the energy-saving help of plain water.
"It's like the red color on San Francisco's Golden Gate Bridge because the environment is very wet," Lee said. "In our case, immersing the wafer and the finished circuit in water significantly reduces the mechanical peel tension and is environmentally friendly."
A ductile metal layer, such as nickel, which is inserted between the electronic film and the silicon wafer, makes the peeling possible in water. This thin-film electronics can then be cut to each surface and adhered to give this object electronic properties.
For example, placing one of the stickers on a flowerpot may cause this flowerpot to detect temperature changes that could affect the surface growth of the plant.
Lee's lab also showed that the components of electronic integrated circuits work just as well before and after they are made into a thin film that has been stripped of a silicon wafer. The researchers used a film to turn an LED light display on and off.
"We optimized this process to delaminate electronic films from wafers without fail," Lee said.
This technology holds a non-provisional US patent. The work was supported by the Purdue Research Foundation, the Air Force Research Laboratory (AFRL-S-114-054-002), the National Science Foundation (NSF-CMMI-1728149), and the University of Virginia.
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