A new method for getting semi-conducting polymers in line could pave the way for cheaper, greener, “paint-on” plastic electronics. A Michigan Engineering team created a liquid polymer solution that they could brush over a surface, automatically aligning the molecules with one another in the direction of the stroke.
The researchers stopped the unaligned polymers from forming large chunks by adding flexible arms that extended off to the sides of the flat, wire-like polymer. These arms prevented too much close contact among the polymers while the bulkiness of the arms kept them from snagging on one another.
They made molecules that matched their design and built a device for spreading the polymer solution over surfaces such as glass or a flexible plastic film. The force from the silicon blade, moving at a constant speed across the liquid polymer, was enough to align the molecules.
The team then built the semiconducting film into a simple transistor, a version of the electronic components that make up computer processors. The device demonstrated the importance of the polymer alignment by showing that charge carriers moved 1,000 times faster in the direction parallel to the silicon blade’s brush-stroke than they did when crossing the direction of the stroke.
According to the researchers, the technique will work equally well with atomic-scale pen nibs or large trowel-like applicators for making electronics of all sizes such as LED displays or light-absorbing coatings for solar cells.
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