Chad Mirkin, director of Northwestern's International Institute for Nanotechnology, and the original developer of the technology behind NanoInk, which went bust earlier this year, is behind new research that employs beam-pen lithography to produce diverse structures at a fraction of the cost of today's nanofabrication technology.
At first, when the technology behind NanoInk was commercially launched, it was difficult to see how using an atomic force microscope-based dip-pen to execute lithography on the nanoscale would be scalable. As Tim Harper noted on this blog when NanoInk filed for bankruptcy, “NanoInk's offering was the equivalent of replacing the printing press with a bunch of monks. Illuminated manuscripts can look good but if you can't mass produce things there isn't a business.”
One of the key differences between this latest research, which was published in the journal Nature Communications (“Desktop nanofabrication with massively multiplexed beam pen lithography”), and NanoInk's original technology is that it employs relatively inexpensive components and still gives you nearly the same capabilities as an expensive AFM. It also operates pretty much like photolithographic techniques do, in that the light strikes a photosensitive substrate to generate structures. However, in this case the instrument can produce structures that range from the macro scale down to the nano scale in one go around.
“With this breakthrough, we can construct very high-quality materials and devices, such as processing semiconductors over large areas, and we can do it with an instrument slightly larger than a printer," said Mirkin in the press release. “"Instead of needing to have access to millions of dollars, in some cases billions of dollars of instrumentation, you can begin to build devices that normally require that type of instrumentation right at the point of use."
The inexpensive components used in the new instrument include beam-pen lithography (BPL) pen arrays. BPLs are structures consisting of arrays of polymeric pyramids that have been coated with an opaque layer; each has a 100-nanometer aperture at the tip. A single beam of light is projected through a digital micromirror device so that the light is broken up into thousand of individual beams. Each one of these beams of lights travels down the pyramidal pens in the array and through the apertures at their tip.
"There is no need to create a mask or master plate every time you want to create a new structure," Mirkin said. "You just assign the beams of light to go in different places and tell the pens what pattern you want generated."
The instrument is a brilliant piece of engineering and its development involved advances in the hardware and software that directs the light to go in the right places. However, it should be noted that this still is essentially top-down manufacturing and should not be confused with so-called “desk-top manufacturing”, which in theory would involve molecular assemblers building both nano-scale and macro-scale structures from the bottom up, atom by atom.
While it may not be molecular manufacturing, it does have the benefit of being available in the not-too-distant future. Mirkin believes that since the instrument uses components that are easily accessible a commercial product could be available in the next two years.
Images showing the diversity of patterns that can be created with the desktop nanofabrication system.
Image: X. Liao