Printing Nanomaterials by Plasma Jet Deposition

Researchers from NASA Ames Research Center and SLAC National Accelerator Laboratory in California, have recently published a novel printing solution that aims to resolve the increasing demand on creating flexible electronics that can be attached to a myriad of wearable, flexible and uneven surfaces.

In their publication, they present a method that passes a helium plasma through a specially designed nozzle while carrying the atomized material of interest.  The helium plasma focuses the deposition of the material on the surface and creates a nice uniform thin layer much like using a spray gun to paint but on a smaller scale and using materials that traditionally were printed using inkjet or aerosol printing.

On one hand, nanomaterial inkjet printing requires the material to be dissolved in a liquid, much like an ink.  The downside is that not all nanomaterials dissolve well to form inks, ie be liquid and uniform enough to prevent clotting of the nozzle jets. Additionally, inkjet printing is limited to a certain type of relatively firm substrates like paper or acetate. Inkjet printing on flexible substrates or 3-dimensional surfaces is not very practical.

On the other hand, depositing nanomaterials using aerosol jet printing is more flexible in terms of printing on different substrates or surfaces.  The problem is, in order to improve the quality of the deposited films, sintering includes a lot of heat, sometimes hundreds of degrees. At this temperatures, most combustible organic substrate will burn.  Also, there is the limitation on the nanomaterials that can be heated at high temperatures without being burned or changing its structure.

The operation principle of this device is similar to the atomizing effect of aerosol jet printing.  The addition of the plasma gas by flowing of helium under a high voltage electric field yields a highly directional and dense printing of the sprayed material.  This translates into creating very dense films whose electrical performance were 2 orders of magnitude better than films created using standard aerosol printing. All of this, with the advantage that this is a device that creates the plasma at atmospheric pressure and the temperature close to the deposition spot is around 40 °C (104 °F).

Aerosol jet compared to Plasma jet. (Left) the printed material scatters easily. The material is wasted and the deposition is not uniform. (Right) The printed material is forced to remain close within the plasma beam and makes for a much denser deposition. CREDIT: NASA Ames Research Center

This operation temperature means paper, plastic substrates and fabrics are safe to function as substrates for novel sensing or communication applications.  “You can use it to deposit things on paper, plastic, cotton, or any kind of textile,” said Meyya Meyyappan of NASA Ames Research Center and one of the authors of this study.

Why printing nanomaterials is so important?

Printing of nanomaterials on virtually any surface, 3-dimensional structures and fabrics opens the doors to smart goods and brings us one step closer to the internet of things.  Imagine being able to monitor all sorts of physiological conditions with your clothes. Sensors that can be printed in band-aids than can bend and accommodate any shape in the body.  Gas sensors printed in paper that once used could be easily disposed and replaced.

The authors printed electrodes of multi-walled Carbon Nanotubes on paper and used it to detect ammonia down to 10ppm. This performance matches the one from detectors built on silicon substrates and printed electronics but at a fraction of the fabrication cost.

This publication can be found at, SOURCE.