For years people have wanted to make circuits using a printer like in their home on paper. The possiblibilities in the near future to make 'rapid-prototyping circuits, integrated circuit on paper, sensors, functional RFID tags on books, even daily life personal electronics and educational training are endless. This concept is called Printed-Circuits-on-Paper (PCP). The idea is to make new devices, faster, cheaper and potentially disposable. Conventionally metal is deposited on a surface using a number of complex methods. But can you make this faster and do this with a regular desktop printer? The answer is yes!
There is a problem with doing this. The main problem people face in this field is to get the material they are printing with to the correct surface tension. The surface tension of the metal has to be correct in order to spray in the right size on the substrate. Now scientists in China have made developed a method to print flexible electronic circuits on paper using liquid metal ink. Electronic inks are more difficult because they have an extremely large surface tension.
How did this team from Beijing do this? Firstly, the scientists improved the adhesion of liquid metal alloy ink by an oxidation strategy. The team designed new print machinery to overcome the high surface tension of the ink. Generally you would want the surface tension to be from 37-60 mN/m depending on the substrate and the properties of the ink. This new machinery has a brush-like porous pinhead (looks a little bit like a mascara brush). The last step involved a specially coated paper (changing the substrate) that offered this special ink to attach easier. The scientists tested a number of different papers and used AFM to compare their properties. They mention that the whole printing process can be done at room temperature using an office printer. This is the future!
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