Nanoprinting
Ink-jet manufacturing for faster plastic electronics

Results: Using conventional ink-jet printing equipment, Henning Sirringhaus of the University of Cambridge in England and colleagues built organic-polymer circuits with switching speeds more than 100 times greater than those of existing polymer circuits. They printed circuit features that they estimated to be smaller than 100 nanometers, less than one-one-hundredth the size of the smallest features previously produced through ink-jet printing.

Why it Matters: Thin, flexible, and cheap plastic electronics could have many applications, from solar cells to radio frequency identification labels in product packaging. Ink-jet printing is an attractive manufacturing option because it deposits materials quickly and cheaply over large areas. But so far, it has yielded features no smaller than 20 micrometers, while the features of typical integrated circuits measure tens of nanometers. The Cambridge team seems to have broken the resolution barrier, making ink-jet printing viable.

Methods: The researchers produced their ultrasmall features using a homebuilt ink-jet printer. They deposited a conducting polymer “ink” as droplets on glass. They then chemically modified the droplets’ surfaces so they would repel additional droplets. A second set of droplets was applied; these flowed off of the first set, landing a tiny distance away. That distance represents the smallest feature size this technique can achieve. The researchers laid out transistors: the closely spaced droplets formed electrodes, and an organic semiconductor filled the gap between them. The researchers estimated the width of this gap based on the performance of the transistors.

Next Step: The researchers are now using better-performing organic semiconducting materials. They are also producing circuits that involve hundreds of interconnected transistors. – By Corie Lok

Source: Sele, C. W., et al. 2005. Lithography-free, self-aligned inkjet printing with sub-hundred-nanometer resolution. Advanced Materials 17:997-1001.