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Printing Electronic Surfaces
Posted on January 4th, 2017 by Chris Walker in New Materials & Applications
There have been some incredible enabling technologies throughout history, which have opened up possibilities we so often now take for granted. While there is plenty of exciting technology under development out there, modern printing techniques look set to be an important enabler of a world which can only exist in science fiction at the moment.
3D printing is getting better all the time, and its application is making its way into the mainstream more and more. But potentially even more significant could be the developments being made in printable electronics.
What’s The Big Deal?
Although all of the potential applications of low-cost printed electronics are not yet known, there are some obvious technologies that would clearly benefit from the technique being developed.
With transistors being printed at a scale small enough to control individual pixels in high-resolution displays, one of the most exciting ways to exploit improvements in printing electronics would be in very thin and lightweight functional surfaces. Examples of this technology in action might include an electronic sticker on the side of a take-away cup letting you know the precise temperature of your coffee. Or intelligent food packaging with a digital countdown to its contents expiration date. The application of this type of technology could be far reaching.
Shorter term implementation of high resolution electronic printing might be in the development of very lightweight touchscreens or the rapid, low-cost prototyping of PCBs.
The Printing Process
There has been talk for a few years now of using inkjet printing techniques to print electronic surfaces. But the results haven’t quite lived up to expectations. Another common approach has been to use a rubber-stamp technique.
The problem with both of these methods is that they are only able to give limited control over the size and thickness of the layer that’s being printed at these small scales. The ink tends to spill into areas it’s not intended to be, or can be distributed unevenly. In either case, the resulting print often has less fidelity than is required for real-world use.
A team at MIT, with the support of the National Science Foundation and the MIT Energy Initiative, have been working on a different approach.
The team, who have a background in making carbon nanotubes, have applied their expertise to the printing problem. They’ve developed a “nanoporous” stamp (which, according the this article is a “stamp that’s more spongy than rubber and shrunk to the size of a pinky fingernail, with patterned features that are much smaller than the width of a human hair.”)
The stamp allows a solution of nanoparticles to flow uniformly onto the printing surface, which gives a much higher resolution than either the inkjet or rubber-stamping approach.
The team have drawn on their experience of growing carbon nanotubes to develop patterns of nanotubes on a surface of silicon. After infusing the stamp with electronic ink (which contains the nanoparticles to be printed), the stamp is pressed onto a substrate, and the nanoparticles are transferred.
Even pressure needs to be applied to the stamp to ensure a high-quality finish, which has lead the team to develop models to predict the necessary force to be applied. They’ve demonstrated the ability to print electronic surfaces at a rate comparable with current industrial printing technologies, with a tenfold improvement in resolution.
The impact of this technology being made available at an industrial scale will be significant, and we could start seeing some innovative uses of very lightweight electronic devices.
The next steps for the team at MIT include continuing to optimize the printing process, as well as looking at the application of this approach to other materials. They have their eyes set on implementing these printing technologies with graphene, to “enable new, ultrathin electronic and energy conversion devices”.
This field looks sure to continue attracting significant interest, and investment, over the coming years.
All opinions shared in this post are the author’s own.
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