Tag Archives: nanopatterning

Nano crafts class: get out your ‘paper’ and scissors

It’s not all atomic force microscopy and nanotweezers as scientists keep reminding us that the techniques we learned in kindergarten can be all the high technology we need even when working at the nanoscale. From the Nov. 14, 2012 news item on ScienceDaily,

Two Northwestern University researchers have discovered a remarkably easy way to make nanofluidic devices: using paper and scissors. And they can cut a device into any shape and size they want, adding to the method’s versatility.

The Nov. 14, 2012 Northwestern University news release by Megan Fellman explains both nanofluidic devices and the new technique,

Nanofluidic devices are attractive because their thin channels can transport ions — and with them a higher than normal electric current — making the devices promising for use in batteries and new systems for water purification, harvesting energy and DNA sorting.

The “paper-and-scissors” method one day could be used to manufacture large-scale nanofluidic devices without relying on expensive lithography techniques.

The Northwestern duo found that simply stacking up sheets of the inexpensive material graphene oxide creates flexible “paper” with tens of thousands of very useful channels. A tiny gap forms naturally between neighboring sheets, and each gap is a channel through which ions can flow.

Using a pair of regular scissors, the researchers simply cut the paper into a desired shape, which, in the case of their experiments, was a rectangle.

“In a way, we were surprised that these nanochannels actually worked, because creating the device was so easy,” said Jiaxing Huang, who conducted the research with postdoctoral fellow Kalyan Raidongia. “No one had thought about the space between sheet-like materials before. Using the space as a flow channel was a wild idea. We ran our experiment at least 10 times to be sure we were right.”

The process is a little more complex than kindergarten crafts (from Fellman’s news release),

To create a working device, the researchers took a pair of scissors and cut a piece of their graphene oxide paper into a centimeter-long rectangle. They then encased the paper in a polymer, drilled holes to expose the ends of the rectangular piece and filled up the holes with an electrolyte solution (a liquid containing ions) to complete the device.

Next they put electrodes at both ends and tested the electrical conductivity of the device. Huang and Raidongia observed higher than normal current, and the device worked whether flat or bent.

The nanochannels have significantly different — and desirable — properties from their bulk channel counterparts, Huang said. The nanochannels have a concentrating effect, resulting in an electric current much higher than those in bulk solutions.

Graphene oxide is basically graphene sheets decorated with oxygen-containing groups. It is made from inexpensive graphite powders by chemical reactions known for more than a century.

Scaling up the size of the device is simple. Tens of thousands of sheets or layers create tens of thousands of nanochannels, each channel approximately one nanometer high. There is no limit to the number of layers — and thus channels — one can have in a piece of paper.

To manufacture very massive arrays of channels, one only needs to put more graphene oxide sheets in the paper or to stack up many pieces of paper. A larger device, of course, can handle larger quantities of electrolyte.

Kindergarten techniques worked well for Andre Geim and Konstantin Novoselov who received Nobel prizes for their work on graphene (from my Oct. 7,2010 posting),

The technique that Geim and Novoselov used to create the first graphene sheets both amuses and fascinates me (from the article by Kit Eaton on the Fast Company website),

The two scientists came up with the technique that first resulted in samples of graphene–peeling individual atoms-deep sheets of the material from a bigger block of pure graphite. The science here seems almost foolishly simple, but it took a lot of lateral thinking to dream up, and then some serious science to investigate: Geim and Novoselo literally “ripped” single sheets off the graphite by using regular adhesive tape.

Then, there’s the ‘Shrinky Dinks’ nanopatterning technique (from my Aug. 16,2010 posting),

Scientists at a Northwestern University laboratory have taken to using a children’s arts and crafts product, Shrinky Dinks, for a new way to create large area nanoscale patterns on the cheap.

It’s good to be reminded that science at its heart is not about expensive equipment and complicated techniques but a means of exploring the world around us with the means at hand.

Using Shrinky Dinks for SANE nanopatterning

I’m charmed. Scientists at a Northwestern University laboratory have taken to using a children’s arts and crafts product, Shrinky Dinks, for a new way to create large area nanoscale patterns on the cheap. First, something more about the Shrinky Dinks (from their website),

We are the Originators and Manufacturers of SHRINKY DINKS shrinkable plastics.

The very first SHRINKY DINKS were sold on October 17, 1973 at Brookfield Square Shopping Mall in Brookfield Wisconsin. Since that time there has been over 250 different Toy Activity and Craft Kits created and marketed.

SHRINKY DINKS SHRINK to approximately 1/3rd their original size and actually become 9 times thicker. Simply place the SHRINKY DINKS piece you created into a Home Oven or Toaster Oven for 2 magic minutes. Watch as your creation gets smaller and smaller.

It’s “MAGICAL” and it’s so quick and easy to do!

There’s also a video (sadly I can’t embed it here)  about the origins, some very simple science, and ideas on how to use Shrinky Dinks.

As for the scientists, there’s no word on how they decided to use this  product for their work (from the news item on physorg.com),

“Anyone needing access to large-area nanoscale patterns on the cheap could benefit from this method,” said Teri W. Odom, associate professor of chemistry and Dow Chemical Company Research Professor in the Weinberg College of Arts and Sciences. Odom led the research. “It is a simple, low-cost and high-throughput nanopatterning method that can be done in any laboratory.”

Details of the solvent-assisted nanoscale embossing (SANE) method are published by the journal Nano Letters. The work also will appear as the cover story of the journal’s February 2011 issue.

The method offers unprecedented opportunities to manipulate the electronic, photonic and magnetic properties of nanomaterials. It also easily controls a pattern’s size and symmetry and can be used to produce millions of copies of the pattern over a large area. Potential applications include devices that take advantage of nanoscale patterns, such as solar cells, high-density displays, computers and chemical and biological sensors.

“No other existing nanopatterning method can both prototype arbitrary patterns with small separations and reproduce them over six-inch wafers for less than $100,” Odom said.

ETA Aug. 17, 2010: I emailed the originator of Shrinky Dinks, Betty J. Morris asking her how she came up with the name for her product yesterday. Here is her very kind reply,

You were wondering how we came up with the name Shrinky Dinks…To be honest, we were trying to come up with a name that would describe the process…the pieces “shrink” and they become “small”… what are words that mean small…one of the words we came up with was “dinky”…we thought of Shrink Dinky…Shrink Dinkies…Shrinkie Dinkies but ultimately liked the sound of Shrinky Dinks…it was just trying out different words that we thought might be unique and worthy of getting a Trademark…our product has now been on the market 37 years…we have Shrinky Dinks Trademarks in 42 different countries and there have been over 250 different SD kits created and marketed over the years…who would have ever imagined such a success story… not me…that’s for sure!

The story reminds me of how one writes a poem, playing with words.  As Betty says it is a remarkable story and, for me, the science (nanopaterning)/kid’s play (Shrinky Dinks) connection is the best part.

ETA Aug.17.10: I also contacted Teri W. Odom, professor at Northwestern University about why they use Slinky Dinks in their work. She very kindly responded with this:

Part of what we are interested in is the development of low-cost nanofabrication tools that can create macroscale areas of nanoscale patterns in a single step. For a variety of reasons, this end-product is hard to obtain—even though we and others have chipped away at this problem for years.

As an example, to achieve smaller and smaller separations between patterns, either expensive, top-down serial tools (such as electron beam lithography or scanning probe techniques) or bottom-up assembly methods need to be used. However, the former cannot easily create large areas of patterns, and the latter cannot readily control the separations of patterns.

We needed a way to obtain nanopatterns separated by specific distances on-demand. Here is where the Shrinky Dinks material comes in. My student had read a paper (published in 2007 in Lab on a Chip) about how this material was used to make microscale patterns starting from a pattern printed using a laser printer. I imagine his thought was: if this material could be used for microscale patterns, why not for nanoscale ones? It would be cheap, and it’s easy to order.

So, we combined this substrate with our new molding method—solvent assisted nanoscale embossing (SANE)—and could now heat the material to shrink the spacing between patterns. And thus, in some sense, we made available to any lab some of the capabilities of the billion-dollar nanofabrication industry for less than one-hundred dollars.

There is something pleasing about using an everyday, inexpensive product for high end technology. Brava!

ETA Aug.23.10: Michael Berger has written an in depth article at Nanoterk on this type of nanofabrication which includes an interview with Teri Odom.