This is part of a wave of new methods that are cheaper and have higher throughput than past approaches. (cheaper and easier to use AFMs, Thermochemical nanolithography, nanopantography, DIY AFM parts)
"The goal is to do manufacturing," says John Rogers, a professor of engineering at the University of Illinois, Urbana Champaign. The new printers can use a broad range of materials for manufacturing novel devices, from plastic electronics and flexible displays to photovoltaic cells and new biomedical sensors, says Rogers.
The researchers have demonstrated that the new inkjets can print very precise patterns of electrically conducting polymers and carbon nanotubes; they have also shown that DNA can be printed without damaging it. "It's hard to do this with traditional silicon fabrication techniques," says Rogers.
Nano printing: This image shows a picture of a flower printed using a novel electrohydrodynamic inkjet printer. Each dot is just eight micrometers in diameter and made up of single-walled carbon nanotubes. Credit: University of Illinois, Urbana Champaign
Rogers and his colleagues use a different approach, called electrohydrodynamic inkjet (or e-jet) printing. "We pull the fluids rather than push them," he says.
This involves using electric fields to create the droplets and relies upon there being a certain amount of electrically charged particles, or ions, within the fluid. Capillary forces pull the fluid from its reservoir to form a semispherical droplet hanging from its rim, like a drop of water on a faucet.
By using electrodes to create an electric field between the nozzle tip and the substrate upon which one wants to print the material, it is possible to make the droplet conical, says Rogers. "Ions accumulate at the surface of the fluid, at the apex of the cone," he says. This concentration of ions allows the tip of the cone to break away and form a droplet that's just a fraction of the volume of the cone.
Using this approach, Rogers and his colleagues have shown that they can print lines of a material 700 nanometers wide or individual dots just 250 nanometers in diameter.
In addition to the size of the droplets, the spatial accuracy is also improved, says Rogers. He and his team discovered quite serendipitously that the field used to create the droplet also helps guide the charged droplet toward the target substrate.
Regular printers can eject droplets on the order of between 10,000 and 100,000 times a second. Rogers's e-jets, on the other hand, operate at around 1,000 times a second. One solution is to use arrays of inkjet heads.