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These days, everything is about the internet of things (IoT) network. Billions of objects ranging from smartphones and watches to buildings, machine parts and medical devices have become wireless sensors of their environments, expanding the IoT.
Whether it is technology, furniture or even office supplies — society is progressively moving towards connecting all objects to the internet. However, how can we connect objects that aren’t ‘tech’ in the first place? It doesn’t seem plausible to be able to connect your couch, which is seemingly just a wooden structure with stuffing and fabric, to the internet? In order to get all objects talking to each other, the technology that enables these objects to communicate and sense each other will need to be scaled up.
This is where researchers at Purdue University and the University of Virginia believe they can help. A team of researchers between the two universities have developed a new fabrication method that makes tiny, thin-film electronic circuits peel-able from a surface. The technique not only eliminates several manufacturing steps and the associated costs, but also allows any object to sense its environment or be controlled through the application of an electronic sticker.
“We could customize a sensor stick it in a drone, and send the drone to the 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 built on their own silicon ‘wafer,’ which is a flat and rigid substrate. The silicon wafer can then withstand the high temperatures and chemical etching that are used to remove the circuits from the wafer.
However high temperatures and etching can damage the silicon wafer, forcing the manufacturing process to accommodate an entirely new wafer each time. Lee has addressed this issue through a new fabrication technique called ‘transfer printing,’ which cuts down manufacturing costs by using a single wafer to build a nearly infinite number of thin films holding electronic circuits. Furthermore, these wafers do not require the need for high temperatures and/or chemicals, instead the film can easily peel off at room temperature with the help of water — a very energy efficient and eco-friendly combination.
“It’s like the red paint on San Francisco’s Golden Gate Bridge — paint peels because the environment is very wet,” Lee comments. “So in our case, submerging the wafer and completed circuit in water significantly reduces the mechanical peeling stress and is environmentally-friendly.
But how is the electronic sticker able to peel off? A ductile metal layer, such as nickel, inserted between the electronic film and the silicon wafer which makes the peeling possible in the water. These thin-film electronics can then be trimmed and pasted onto any surface, granting that object electronic features. For example, putting one of the stickers on a flower pot made the flower pot capable of sensing 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.
Eventually after further testing and deployment, these stickers could also facilitate wireless communication. The researchers demonstrate capabilities on various objects in a paper recently published in the Proceedings of the National Academy of Sciences.
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