Tag Archives: printing

Printing in midair

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Dexter Johnson’s May 16, 2016 posting on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website) was my first introduction to something wonder-inducing (Note: Links have been removed),

While the growth of 3-D printing has led us to believe we can produce just about any structure with it, the truth is that it still falls somewhat short.

Researchers at Harvard University are looking to realize a more complete range of capabilities for 3-D printing in fabricating both planar and freestanding 3-D structures and do it relatively quickly and on low-cost plastic substrates.

In research published in the journal Proceedings of the National Academy of Sciences (PNAS),  the researchers extruded a silver-nanoparticle ink and annealed it with a laser so quickly that the system let them easily “write” free-standing 3-D structures.

While this may sound humdrum, what really takes one’s breath away with this technique is that it can create 3-D structures seemingly suspended in air without any signs of support as though they were drawn there with a pen.

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Laser-assisted direct ink writing allowed this delicate 3D butterfly to be printed without any auxiliary support structure (Image courtesy of the Lewis Lab/Harvard University)

Laser-assisted direct ink writing allowed this delicate 3D butterfly to be printed without any auxiliary support structure (Image courtesy of the Lewis Lab/Harvard University)

A May 16, 2016 Harvard University press release (also on EurekAlert) provides more detail about the work,

“Flat” and “rigid” are terms typically used to describe electronic devices. But the increasing demand for flexible, wearable electronics, sensors, antennas and biomedical devices has led a team at Harvard’s John A. Paulson School of Engineering and Applied Sciences (SEAS) and Wyss Institute for Biologically Inspired Engineering to innovate an eye-popping new way of printing complex metallic architectures – as though they are seemingly suspended in midair.

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“I am truly excited by this latest advance from our lab, which allows one to 3D print and anneal flexible metal electrodes and complex architectures ‘on-the-fly,’ ” said Lewis [Jennifer Lewis, the Hansjörg Wyss Professor of Biologically Inspired Engineering at SEAS and Wyss Core Faculty member].

Lewis’ team used an ink composed of silver nanoparticles, sending it through a printing nozzle and then annealing it using a precisely programmed laser that applies just the right amount of energy to drive the ink’s solidification. The printing nozzle moves along x, y, and z axes and is combined with a rotary print stage to enable freeform curvature. In this way, tiny hemispherical shapes, spiral motifs, even a butterfly made of silver wires less than the width of a hair can be printed in free space within seconds. The printed wires exhibit excellent electrical conductivity, almost matching that of bulk silver.

When compared to conventional 3D printing techniques used to fabricate conductive metallic features, laser-assisted direct ink writing is not only superior in its ability to produce curvilinear, complex wire patterns in one step, but also in the sense that localized laser heating enables electrically conductive silver wires to be printed directly on low-cost plastic substrates.

According to the study’s first author, Wyss Institute Postdoctoral Fellow Mark Skylar-Scott, Ph.D., the most challenging aspect of honing the technique was optimizing the nozzle-to-laser separation distance.

“If the laser gets too close to the nozzle during printing, heat is conducted upstream which clogs the nozzle with solidified ink,” said Skylar-Scott. “To address this, we devised a heat transfer model to account for temperature distribution along a given silver wire pattern, allowing us to modulate the printing speed and distance between the nozzle and laser to elegantly control the laser annealing process ‘on the fly.’ ”

The result is that the method can produce not only sweeping curves and spirals but also sharp angular turns and directional changes written into thin air with silver inks, opening up near limitless new potential applications in electronic and biomedical devices that rely on customized metallic architectures.

Seeing is believing, eh?

Here’s a link to and a citation for the paper,

Laser-assisted direct ink writing of planar and 3D metal architectures by Mark A. Skylar-Scott, Suman Gunasekaran, and Jennifer A. Lewis. PNAS [Proceedings of the National Academy of Sciences] 2016 doi: 10.1073/pnas.1525131113

I believe this paper is open access.

A question: I wonder what conditions are necessary before you can 3D print something in midair? Much as I’m dying to try this at home, I’m pretty that’s not possible.

Nanography™ at the 2016 Drupa international trade show

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Drupa is the largest printing equipment trade show and exhibition in the world (Wikipedia essay) and the 2016 edition is being held from May 31 – June 10, 2016 in Dusseldorf, Germany. As he did in 2012 (see my May 18, 2012 post), Benny Landa (a legendary figure in the printing equipment industry) is presenting nanotechnology-enabled printing presses. I gather 2012 featured a ‘concept’ presentation, which included the introduction of a new ink (NanoInk™) and this 2016 presentation will feature a working press. A May 6, 2016 article by Naomi Webb for Tech Guru Daily describes Landa’s position in the industry and his new presses (Note: The writer does not seem very familiar with nanotechnology),

One thing is certain about the upcoming Drupa show in Dusseldorf: you can expect a high level of excitement around Landa. The firm is the brainchild of Benny Landa – the ‘father of digital printing’ and a man described as the print industry’s Steve Jobs by Print Week. …

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As Landa himself told Print Week: “The crucial difference is that all processes where wet ink contacts paper suffer from the same problems. Water wicks along the paper fibres and it’s very, very difficult to dry it with so much water in the paper. Therefore, inkjet is limited. It’s either high-speed or high area coverage, but not both.

“The fact that there is no ink-paper interaction is the fundamental difference with Nanography [printing concept/technology]. No matter what you transfer to you get an identical image.” …

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It [Landa Company] will put on five 30-minute theatre presentations a day and arcade to showcase its inventions, with demonstrations to run on the S10, S10P and W10 Nanographic Printing Presses. On top of that, the Landa L50 Nano-Metallography Module will be used to print metallized labels on a conventional narrow web press.

I wonder if these new products are open systems. Landa’s last company featured equipment (Indigo) with a proprietary or closed system (meaning that if a printer had one piece of Indigo equipment, every other connecting piece also had to be an Indigo product).

Silky smooth tissue engineering

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Virginia Commonwealth University (VCU) researchers have announced a new technique for tissue engineering that utilizes silk proteins. From a May 13, 2014 news item on Nanowerk,

When most people think of silk, the idea of a shimmering, silk scarf, or luxurious gown comes to mind.

But few realize, in its raw form, this seemingly delicate fiber is actually one of the strongest natural materials around – often compared to steel.

Silk, made up of the proteins fibroin and sericin, comes from the silkworm, and has been used in textiles and medical applications for thousands of years. The [US] Food and Drug Administration has classified silk as an approved biomaterial because it is nontoxic, biodegradable and biocompatible.

Those very properties make it an attractive candidate for use in widespread applications in tissue engineering. One day, silk could be an exciting route to create environmentally sound devices called “green devices,” instead of using plastics. However, forming complex architectures at the microscale or smaller, using silk proteins and other biomaterials has been a challenge for materials experts.

Now, a team of researchers from the Virginia Commonwealth University School of Engineering has found a way to fabricate precise, biocompatible architectures of silk proteins at the microscale.

A May 12, 2014 VCU news release by Sathya Achia Abraham, which originated the news item, describes the research underlying two recently published papers by the research team

    Kurland [Nicholas Kurland, Ph.D.] and Yadavalli [Vamsi Yadavalli, Ph.D., associate professor of chemical and life science engineering] successfully combined silk proteins with the technique of photolithography in a process they term “silk protein lithography” (SPL). Photolithography, or “writing using light,” is the method used to form circuits used in computers and smartphones, Yadavalli said.

According to Yadavalli, SPL begins by extracting the two main proteins from silk cocoons. These proteins are chemically modified to render them photoactive, and coated on glass or silicon surfaces as a thin film. As ultraviolet light passes through a stencil-like patterned mask, it crosslinks light-exposed proteins, turning them from liquid to solid.

The protein in unexposed areas is washed away, leaving behind patterns controllable to 1 micrometer. In comparison, a single human hair is 80-100 micrometers in diameter.

“These protein structures are high strength and excellent at guiding cell adhesion, providing precise spatial control of cells,” Yadavalli said.

“One day, we can envision implantable bioelectronic devices or tissue scaffolds that can safely disappear once they perform their intended function,” he said.

The team’s current research focuses on combining the photoreactive material with techniques such as rapid prototyping, and developing flexible bioelectronic scaffolds.

Study collaborators included S.C. Kundu, Ph.D., professor of biotechnology at the Indian Institute of Technology Kharagpur in India, and Tuli Dey, Ph.D., postdoctoral associate, at the Indian Institute of Technology Kharagpur in India, who provided the silk cocoons used in the study and assisted with cell culture experiments. VCU has recently filed a patent on this work.

Here’s a link to and a citation for both papers,

Silk Protein Lithography as a Route to Fabricate Sericin Microarchitectures by Nicholas E. Kurland, Tuli Dey, Congzhou Wang, Subhas C. Kundu and Vamsi K. Yadavalli. Article first published online: 16 APR 2014 DOI: 10.1002/adma.201400777

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Precise Patterning of Silk Microstructures Using Photolithography by Nicholas E. Kurland, Tuli Dey, Subhas C. Kundu, and Vamsi K. Yadavalli. Advanced Materials Volume 25, Issue 43, pages 6207–6212, November 20, 2013 Article first published online: 20 AUG 2013 DOI: 10.1002/adma.201302823

© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Both papers are behind a paywall.

I have written about silk proteins in a Nov. 28, 2012 post (Producing stronger silk musically) that briefly mentioned tissue engineering with regard to a new technique for biosynthesising  materials.

Beautiful color printing for encoding high density data

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Researchers at A*STAR (Agency for Science Technology and Research) based in Singapore have printed images at an extraordinary resolution of 100,000 dots per inch according to an Apr. 10, 2013 news item on ScienceDaily,

To print the image, the team coated a silicon wafer with insulating hydrogen silsesquioxane and then removed part of that layer to leave behind a series of upright posts of about 95 nanometers high. They capped these nanoposts with layers of chromium, silver and gold (1, 15 and 5 nanometers thick, respectively), and also coated the wafer with metal to act as a backreflector.

Each color pixel in the image contained four posts at most, arranged in a square. The researchers were able to produce a rainbow of colors simply by varying the spacing and diameter of the posts to between 50 nanometers and 140 nanometers.

When light hits the thin metal layer that caps the posts, it sends ripples — known as plasmons — running through the electrons in the metal. The size of the post determines which wavelengths of light are absorbed, and which are reflected …

Although the current process is not practical, it takes several hours to print an image there are some intriguing benefits,

Printing images in this way makes them potentially more durable than those created with conventional dyes. In addition, color images cannot be any more detailed: two adjacent dots blur into one if they are closer than half the wavelength of the light reflecting from them. Since the wavelength of visible light ranges about 380-780 nanometers, the nanoposts are as close as is physically possible to produce a reasonable range of colors.

The researchers believe there may be applications for anti-counterfeiting tags and encoding high density data.

You can read more about the work and find a citation and link to the researchers’ study published in Nature Nanotechnology at the ScienceDaily news item.

Benny Landa and nanoprinting

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There’s one more announcement from DRUPA (the 2012 edition of the International Trade Fair for prepress, premedia, printing, book binding, print finishing and paper converting held May 3 – 16, 2012) that I want to feature here, especially since it’s nanotechnology-related.  From the May 17, 2012 news item on Nanowerk,

Landa Corporation announced the details of its groundbreaking Landa Nanographic Printing™ Presses that are set to transform mainstream commercial, packaging and publishing markets. With output speeds comparable to offset presses and employing NanoInk™ colorants that create unprecedented image qualities, the Landa Nanographic Printing™ Press portfolio is set to fundamentally change printing as we know it.

Landa Founder, Chairman and CEO Benny Landa says, “Nanography™ is a new technology for applying ink to paper. In developing Landa Nanographic Printing we had to re-think and reinvent the printing press. The result is digital printing with remarkable performance – from a family of presses that share stunning ergonomic design, a small footprint and some of the most advanced user functionality available in the market.”

There is very little technical detail which is typical of Landa’s approach. As I recall from my days working for a competitor, Indigo, Landa’s last printing company, sold presses built on proprietary software. Any printer who purchased Indigo products was locked into the ‘Indigo world’ as there was no possibility of mixing and matching products from other manufacturers.

On that note, I notice this reference to a propriety ink in Landa’s latest product announcement (May 17, 2012 news item),

At the heart of the Nanographic Printing™ process are Landa NanoInk™ colorants. Comprised of pigment particles only tens of nanometres in size (1 nanometer is about 100,000 times thinner than a human hair), these nano-pigments are extremely powerful absorbers of light and enable unprecedented image qualities. Landa Nanographic Printing is characterised by ultra-sharp dots of extremely high uniformity, high gloss fidelity and the broadest colour gamut of any four-colour printing process.

Nanographic Printing begins with the ejection of billions of microscopic droplets of water-based Landa NanoInk onto a heated blanket conveyor belt. Each droplet of aqueous NanoInk lands at a precise location on the belt, creating the colour image. As the water evaporates, the ink becomes an ultra-thin dry polymeric film, less than half the thickness of offset images.

The resulting image is then transferred to any kind of ordinary paper, coated or uncoated, or onto any plastic packaging film – without requiring pre-treatment. The NanoInk film image instantaneously bonds to the surface, forming a tough, abrasion-resistant laminated layer without leaving any residual ink on the blanket.

Since NanoInk images are already dry, there is no need for post drying. Two-sided printing becomes simple and printed goods can be immediately handled, right off the press, even in the most aggressive finishing equipment.

Given that the printing industry is not experiencing growth these days, it’ll be interesting to see if this ‘nano’ approach is going to work. My last posting about the 2012 DRUPA focused on 3-D printing and paper loudspeakers (May 4, 2012).

Coatings that shake off bacteria and biological photocopying

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The American Vacuum Society (AVS) is holding its 58th International Symposium and Exhibition from Oct. 30 – Nov. 4, 2011 in Nashville, Tennessee. Presentations are not focused on vacuuming (hoovering) floors but rather on something called vacuum science and they span from a presentation on bacteria and coatings to another on photocopying DNA to more.

From the Oct. 31, 2011 news item on Nanowerk,

“Sea water is a very aggressive biological system,” says Gabriel Lopez, whose lab at Duke University studies the interface of marine bacterial films with submerged surfaces. While the teeming abundance of ocean life makes coral reefs and tide pools attractive tourist destinations, for ships whose hulls become covered with slime, all this life can, quite literally, be a big drag. On just one class of U.S. Navy destroyer, biological build-up is estimated to cost more than $50 million a year, mostly in extra fuel, according to a 2010 study performed by researchers from the U.S. Naval Academy and Naval Surface Warfare Center in Maryland. Marine biofouling can also disrupt the operation of ocean sensors, heat-exchangers that suck in water to cool mechanical systems, and other underwater equipment.

I think rather than describing sea water as ‘aggressive’  which suggests intent, I’d use ‘active’ as Lopez does later in another context (excerpted from the news item),

Lopez and his group focus on a class of materials called stimuli-responsive surfaces. As the name implies, the materials will alter their physical or chemical properties in response to a stimulus, such as a temperature change. The coatings being tested in Lopez’s lab wrinkle on the micro- or nano-scale, shaking off slimy colonies of marine bacteria in a manner similar to how a horse might twitch its skin to shoo away flies. The researchers also consider how a stimulus might alter the chemical properties of a surface in a way that could decrease a marine organism’s ability to stick.

At the AVS Symposium, held Oct. 30 – Nov. 4 in Nashville, Tenn., Lopez will present results from experiments on two different types of stimuli-responsive surfaces: one that changes its texture in response to temperature and the other in response to an applied voltage. The voltage-responsive surfaces are being developed in collaboration with the laboratory of Xuanhe Zhao, also a Duke researcher, who found that insulating cables can fail if they deform under voltages. “Surprisingly, the same failure mechanism can be made useful in deforming surfaces of coatings and detaching biofouling,” Zhao said.

“The idea of an active surface is inspired by nature,” adds Lopez, who remembers being intrigued by the question of how a sea anemone’s waving tentacles are able to clean themselves. [emphasis mine] Other biological surfaces, such as shark skin, have already been copied by engineers seeking to learn from nature’s own successful anti-fouling systems.

(I did profile some biomimicry work being done with shark skin in my comments on part 4 of the Making Stuff programmes broadcast as part of the Nova series on PBS (US Public Broadcasting Stations) in my Feb. 10, 2011 posting.)

This next presentation is in the area of synthetic biology. From the Oct. 31, 2011 news item (DNA origami from inkjet synthesis produced strands) on Nanowerk,

In the emerging field of synthetic biology, engineers use biological building blocks, such as snippets of DNA, to construct novel technologies. One of the key challenges in the field is finding a way to quickly and economically synthesize the desired DNA strands. Now scientists from Duke University have fabricated a reusable DNA chip that may help address this problem by acting as a template from which multiple batches of DNA building blocks can be photocopied. The researchers have used the device to create strands of DNA which they then folded into unique nanoscale structures.

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“We found that we had an “immortal” DNA chip in our hands,” says Ishtiaq Saaem, a biomedical engineering researcher at Duke and member of the team. [emphasis mine] “Essentially, we were able to do the biological copying process to release material off the chip tens of times. [emphasis mine] The process seems to work even using a chip that we made, used, stored in -20C for a while, and brought out and used again.”

After releasing the DNA from the chip, the team “cooked” it together with a piece of long viral DNA. “In the cooking process, the viral DNA is stapled into a desired shape by the smaller chip-derived DNA,” explains Saaem. One of the team’s first examples of DNA origami was a rectangle shape with a triangle attached on one side, which the researchers dubbed a “nano-house.” The structure could be used to spatially orient organic and inorganic materials, serve as a scaffold for drug delivery, or act as a nanoscale ruler, Saaem says.

I’m not very comfortable with the notion of an “immortal DNA chip” but then I have many reservations about synthetic biology. Still, I think it’s important to pay attention and consider the possibility that my fears about synthetic biology might make as much sense as the fears many had about electricity in the 19th century.