The Internet of Things (IoT) is an expanding network of connected devices--billions of objects ranging from smartphones and wearables to buildings, machine parts and medical devices--that also often operate as wireless sensors of their environments.
And we're constantly connecting even more objects to the Internet – down to the level of furniture, tools and office supplies – which means that the technology enabling communication and sensing between all these objects will need to scale up quickly and effectively.
In the search for a fast and easy way to turn regular objects into IoT-enabled smart objects, researchers at Purdue University and the University of Virginia have developed a new fabrication method that makes tiny, thin-film electronic flexible circuits that can be applied to and peeled from a surface. These circuits are basically a high-tech sticker, allowing any object to sense its environment or be controlled from another device. The technique used to create these circuits also eliminates several manufacturing steps and the associated costs.
Eventually, the research team sees these stickers being used to facilitate wireless communication.
"We could customize a sensor, stick it onto a drone, and send the drone to dangerous areas to detect gas leaks, for example," said Chi Hwan Lee, assistant professor of biomedical engineering and mechanical engineering at Purdue.
Today, most electronic circuits are individually built on their own flat, rigid silicon “wafer” substrate that can withstand the high temperatures and chemical etching used to remove the circuits from the wafer. But these high temperatures and etching damage the silicon wafer, forcing the manufacturing process to accommodate an entirely new wafer each time.
Lee calls the new fabrication technique “transfer printing,” and explains that it cuts down manufacturing costs by using a single wafer to build a nearly infinite number of thin films holding electronic circuits. The film--with its circuits--can peel off the wafer at room temperature simply using water, instead of high temperatures and chemicals.
“It’s like the red paint on San Francisco’s Golden Gate Bridge – the paint peels because the environment is very wet,” Lee said. “So in our case, submerging the wafer and completed circuit in water significantly reduces the mechanical peeling stress and is environmentally friendly.”
A ductile metal layer, such as nickel, is inserted between the electronic film and the silicon wafer to enable the peeling while in water. These thin-film electronics can then be trimmed and pasted onto any surface, granting that object electronic features.
As an example, putting one of the stickers on a flower pot allowed that flower pot to sense temperature changes that could affect the plant’s growth.
Lee’s lab also demonstrated that the components of electronic integrated circuits work just as well before and after they were made into a thin film peeled from a silicon wafer. The researchers used one film to turn an LED light display on and off.
“We’ve optimized this process so that we can delaminate electronic films from wafers in a defect-free manner,” Lee said.
The researchers demonstrate capabilities on various objects in a paper recently published in the Proceedings of the National Academy of Sciences.
For more on innovative flexible circuits, check out these stories:
How To Make Waterproof Graphene Circuits
Electronic Skin for Improved Prosthetics
Source: Purdue University Newsroom