Tag Archives: Printing

Heat-free metallic print can form electronic circuits on soft surfaces (flowers, gelatin)

Martin Thuo of Iowa State University and the Ames Laboratory can show you several remarkable photos in his collection: a curled sheet of paper with a LED display or a rose with metal traces printed on a petal. This isn’t an artistic project — Thuo is working on a new technology which allows printing conductive metallic lines on all kinds of materials, from a wall to a leaf.

This could be a game changer.

Image credits: Martin Thuo.

The technology features liquid metal (alloys of bismuth, indium, and tin) and is remarkable for multiple reasons. For starters, it’s capable of producing extremely small particles, about 10 millionths of a meter across. The resulting print is also not hot, which means you can print it on anything you want — including living things.

The printed metal acts like a quickly-solidifying weld, creating conductive, metallic lines and traces which can be used for electronic circuits.

“This work reports heat-free, ambient fabrication of metallic conductive interconnects and traces on all types of substrates,” Thuo and colleagues write in a recent study.

Through the ‘printing’ process, the metal inside flows and solidifies, creating a heat-free weld or, in this case, printing conductive, metallic lines and traces on all kinds of materials — everything from a concrete wall to a leaf.

The technology could have numerous applications. It could be used to print sensors to measure the growth and state of crops (assessing whether everything is going smoothly, or if they require more water or are being attacked by pests). Similarly, the sensors could be used to monitor the structural integrity of a building. The technology has also been tested in this regard. The researchers used a paper-based setting as a base for the sensor, and the sensor read changes in electrical currents when the paper was curved. Researchers say that, ultimately, the approach could also be used for medical sensors or models for biological tissues (since it can also be printed on soft surfaces such as gelatin). All this is done without damaging the base, even when it’s a living biological system.

Printed electronic traces on gelatin. Image credits: Martin Thuo / Iowa State University.

Initially, this started as a teaching exercise. Thuo wanted to give his undergrad students something to work on that would be both useful and fun.

“I started this with undergraduate students,” he said. “I thought it would be fun to get students to make something like this. It’s a really beneficial teaching tool because you don’t need to solve 2 million equations to do sophisticated science.”

Now it’s grown spectacularly — the university has even sponsored Thuo’s lab with start-up funds to continue working on the technology.

“The students discovered ways of dealing with metal and that blossomed into a million ideas,” Thuo said. “And now we can’t stop.”

The study was published in the journal Advanced Functional Materials.

Round printing.

Novel 3D printing method makes furniture in vats of gel within minutes

MIT and Steelcase researchers have teamed up to revamp 3D printing and throw in a Westworld-esque vibe in the bargain. This new technique injects the material into a supportive gel and can print much larger objects than previously possible in a matter of minutes.

RLP in progress.

Dubbed Rapid Liquid Printing because MIT probably doesn’t have a naming division, the approach forgoes the layer-by-layer approach of traditional 3D printing methods and instead injects material directly into a vat of supportive gel. The injection head essentially ‘draws’ the object inside the vat, with the gel providing buoyancy and maintaining the shape of the object while it hardens.

Round printing.

Image via Youtube.

Altering the speed of injection and the speed at which the head travels through the gel will alter the thickness of lines laid down by the device, allowing for a huge range of shapes to be created.

Printing varying thickness line.

Image via Youtube.

Rapid Liquid Printing 2.

Rapid Liquid Printing 3.

RLP allows for much larger objects to be created much faster and using stronger materials than traditional printing methods. The developers, a mixed team of researchers from the MIT’s Self-Assembly Lab and furniture manufacturer Steelcase, hope the technology will address what they perceive are the main limitations of traditional 3D printing methods: slow manufacturing speed compared to conventional processes such as milling or injection molding, their (usually) small scale, and the narrow range of materials they can use (which are also comparatively lower quality than other industrial materials).

And it works, on all counts. This cool video the developers put together showcases how RLP can be used to print a whole piece of furniture in a matter of minutes. Check it out:

Unless otherwise specified, image credits go to MIT / Selfassemblylab.


UV-printed text allows sheets to be reset and re-used 80 different times

A new technology could change how we think about paper and printing — forever. Based on UV-sensitive paint, the method allows paper to be re-used, making it much cheaper and more sustainable than traditional printing.

A sample of the paper with text.
Image credits Wang et al, (2017) American Chemical Society.

So we’ve seen our fair share of creative ink recipes throughout time — some to grow, some to raise awareness, others made from pee. They’re all awesome. But once ink hits the paper, it’s there for good. If you want to print something else, you need a fresh sheet of paper.

Or do you? A joint US-Chinese team has developed a novel nanoparticle coating which can make traditional inks oh-so-last-year. This blue substance can easily be applied to paper — either by spraying or soaking — and changes color when exposed to concentrated ultraviolet (UV) light. If you need to print something else, just heat the sheet to 120 degrees Celsius (248 Fahrenheit) and voila — the ink ‘resets’. As each sheet of paper allows for more than 80 re-writes, the ink could reduce paper usage in the long run, saving a lot of money and a lot of trees in the process.

I’m blue

Treated paper “has the same feel and appearance as conventional paper, but can be printed and erased repeatedly without the need for additional ink” said teammember Yadong Yin from the University of California, Riverside, for Phys.org.

“Our work is believed to have enormous economic and environmental merits to modern society.”

The team combined two kinds of nanoparticles for the ink. The color is created using Prussian blue particles, a pigment which becomes colorless when it gains electrons. The other ingredient is titanium dioxide (TiO2) particles, which catalyze the photochemical reaction between UV rays and the ink — they release the electrons needed for the reaction.

Image credits Wang et al., (2017) American Chemical Society.

What you get is a beautiful blue color that turns colorless under UV rays. So unlike traditional printing methods, this ink prints the blank spaces of the page instead of the words themselves. Alternatively, you can print the letters only and the text will come out white on a blue backdrop.

The print remains stable for at least five days before the page slowly starts fading back to blue, as pigment particles shed the extra electrons. Or you can just heat it up to reset it as fast as you like.

Applying the coat is a quick and cheap process, and the researchers hope this will promote wide-scale use. As each sheet can be used for 80 or more different prints without further costs, it’s easy to see the commercial appeal of the technology.

Add to that the fact that it also reduces paper use and waste, and you get a real winner. In the US, estimates place up to 40% of waste as discarded paper. All this waste translates to added costs for transport, recycling, or disposal. It also fuels the country’s ever-growing need for paper, an industry which consumes around 68 million trees every year and is one of the dirtiest in the country.

Following the paper trail

Yin first unveiled the prototype ink in December 2014. Its first iteration could only sustain 20 printing cycles, and was trickier to apply onto paper than the current material. The team says they improved the stability, ease of application, and lowered production costs over their previous product.

Now, they’re hard at work taking their technology to a printer near you.

“Our immediate next step is to construct a laser printer to work with this rewritable paper to enable fast printing,” Yin told Phys.org.

“We will also look into effective methods for realizing full-colour printing.”

But my question is — can we make tattoos with this ink?

The full paper “Photocatalytic Color Switching of Transition Metal Hexacyanometalate Nanoparticles for High-Performance Light-Printable Rewritable Paper” has been published in the journal Nano Letters.