|A laptop computer. / Photo by: Marcel De Grijs via 123RF|
Built-in sensors in electronic devices enabled the rising trend of the internet of things. Wireless sensors, machines, gadgets, and autonomous vehicles can become connected in a single ecosystem. To make the expansion of IoT easier, a team of engineers developed electronic stickers to support large-scale ecosystems.
In a traditional use of silicon wafers -- flat and rigid substrate used to produce electronic films -- most manufacturers apply high temperature and chemical etching to remove the circuits. However, the two elements can damage the wafer itself and manufacturers will need another set of wafers to produce the same circuits.
Opposed to the standard method, the engineers tweaked the method to create a new fabrication method called transfer printing. In transfer printing, electronic circuits are built individually on silicon wafers and instead of applying chemical etching and high temperature, they applied water to remove the film from the wafer. The new method allowed them to produce multiple numbers of circuit-bearing thin films from just one wafer.
“It’s like the red paint on San Francisco’s Golden Gate Bridge – paint peels because the environment is very wet. So in our case, submerging the wafer and completed circuit in water significantly reduces the mechanical peeling stress and is environmentally friendly,” explained Chi Hwan Lee, an author of the study from Purdue University.
To use water to help peel off the films, they inserted a ductile metal layer in between the electronic film and the silicon wafer. The electronic films peeled from the wafer can be trimmed and pasted on any surface, equipping that object with electronic features. These circuits can provide ordinary chairs, flower pots, and beds with electronic capabilities. The engineers tested these films and they were able to control an LED light display.
"We could customize a sensor, stick it onto a drone, and send the drone to dangerous areas to detect gas leaks, for example," Lee added.