MIT researchers 3-D print colloidal crystals – For the Scale-Up of optical sensors, color displays, and light-guided electronics + YouTube Video

3-D-printed colloidal crystals viewed under a light microscope. Image: Felice Franke

Technique could be used to scale-up self-assembled materials for use as optical sensors, color displays, and light-guided electronics.

MIT engineers have united the principles of self-assembly and 3-D printing using a new technique, which they highlight today in the journal Advanced Materials.

By their direct-write colloidal assembly process, the researchers can build centimeter-high crystals, each made from billions of individual colloids, defined as particles that are between 1 nanometer and 1 micrometer across.

“If you blew up each particle to the size of a soccer ball, it would be like stacking a whole lot of soccer balls to make something as tall as a skyscraper,” says study co-author Alvin Tan, a graduate student in MIT’s Department of Materials Science and Engineering. “That’s what we’re doing at the nanoscale.”

The researchers found a way to print colloids such as polymer nanoparticles in highly ordered arrangements, similar to the atomic structures in crystals. They printed various structures, such as tiny towers and helices, that interact with light in specific ways depending on the size of the individual particles within each structure.

Nanoparticles dispensed from a needle onto a rotating stage, creating a helical crystal containing billions of nanoparticles. (Credit: Alvin Tan)

The team sees the 3-D printing technique as a new way to build self-asssembled materials that leverage the novel properties of nanocrystals, at larger scales, such as optical sensors, color displays, and light-guided electronics.

“If you could 3-D print a circuit that manipulates photons instead of electrons, that could pave the way for future applications in light-based computing, that manipulate light instead of electricity so that devices can be faster and more energy efficient,” Tan says.

Tan’s co-authors are graduate student Justin Beroz, assistant professor of mechanical engineering Mathias Kolle, and associate professor of mechanical engineering A. John Hart.

Out of the fog

Colloids are any large molecules or small particles, typically measuring between 1 nanometer and 1 micrometer in diameter, that are suspended in a liquid or gas. Common examples of colloids are fog, which is made up of soot and other ultrafine particles dispersed in air, and whipped cream, which is a suspension of air bubbles in heavy cream. The particles in these everyday colloids are completely random in their size and the ways in which they are dispersed through the solution.

If uniformly sized colloidal particles are driven together via evaporation of their liquid solvent, causing them to assemble into ordered crystals, it is possible to create structures that, as a whole, exhibit unique optical, chemical, and mechanical properties. These crystals can exhibit properties similar to interesting structures in nature, such as the iridescent cells in butterfly wings, and the microscopic, skeletal fibers in sea sponges.

So far, scientists have developed techniques to evaporate and assemble colloidal particles into thin films to form displays that filter light and create colors based on the size and arrangement of the individual particles. But until now, such colloidal assemblies have been limited to thin films and other planar structures.

“For the first time, we’ve shown that it’s possible to build macroscale self-assembled colloidal materials, and we expect this technique can build any 3-D shape, and be applied to an incredible variety of materials,” says Hart, the senior author of the paper.

Building a particle bridge

The researchers created tiny three-dimensional towers of colloidal particles using a custom-built 3-D-printing apparatus consisting of a glass syringe and needle, mounted above two heated aluminum plates. The needle passes through a hole in the top plate and dispenses a colloid solution onto a substrate attached to the bottom plate.

The team evenly heats both aluminum plates so that as the needle dispenses the colloid solution, the liquid slowly evaporates, leaving only the particles. The bottom plate can be rotated and moved up and down to manipulate the shape of the overall structure, similar to how you might move a bowl under a soft ice cream dispenser to create twists or swirls.

Beroz says that as the colloid solution is pushed through the needle, the liquid acts as a bridge, or mold, for the particles in the solution. The particles “rain down” through the liquid, forming a structure in the shape of the liquid stream. After the liquid evaporates, surface tension between the particles holds them in place, in an ordered configuration.

As a first demonstration of their colloid printing technique, the team worked with solutions of polystyrene particles in water, and created centimeter-high towers and helices. Each of these structures contains 3 billion particles. In subsequent trials, they tested solutions containing different sizes of polystyrene particles and were able to print towers that reflected specific colors, depending on the individual particles’ size.

“By changing the size of these particles, you drastically change the color of the structure,” Beroz says. “It’s due to the way the particles are assembled, in this periodic, ordered way, and the interference of light as it interacts with particles at this scale. We’re essentially 3-D-printing crystals.”

The team also experimented with more exotic colloidal particles, namely silica and gold nanoparticles, which can exhibit unique optical and electronic properties. They printed millimeter-tall towers made from 200-nanometer diameter silica nanoparticles, and 80-nanometer gold nanoparticles, each of which reflected light in different ways.

“There are a lot of things you can do with different kinds of particles ranging from conductive metal particles to semiconducting quantum dots, which we are looking into,” Tan says. “Combining them into different crystal structures and forming them into different geometries for novel device architectures, I think that would be very effective in fields including sensing, energy storage, and photonics.”

This work was supported, in part, by the National Science Foundation, the Singapore Defense Science Organization Postgraduate Fellowship, and the National Defense Science and Engineering Graduate Fellowship Program.

 

3-D Printing Technology May Soon Change – Revolutionize Our Lives

3D printing, or additive manufacturing, is the process of turning a 2D digital image into a 3D object through printing successive layers of materials until an entire item is created. Initial images are created in design software programs before being realized through 3D printing. The advent of consumer 3D printing has the potential to revolutionize its use as a technology, but also opens up a whole host of intellectual property (IP) debates.

Dr Dinusha Mendis’ research into the intellectual property issues around 3D printing stemmed from a personal interest in the latest technological advances. As Dr Mendis says: “While 3D printing was first developed more than 30 years ago, its expansion into consumer printing is revolutionary. Moving into the consumer market means it is developing rapidly as a technology, which opens up all sorts of questions around intellectual property rights and copyright.” The IP laws in the UK were created long before 3D printing, or any of its associated technologies came about, which means that legislation often lags behind the issues being faced by UK consumers and businesses. It leads to a number of grey areas, many of which Dr Mendis has tackled in her recent research for the UK Intellectual Property Office (“A legal and empirical study into the intellectual property implications of 3D printing”), in collaboration with Econolyst, the leading 3D printing and additive manufacturing company in the UK. As a technology, 3D printing has the potential to impact on a vast number of markets, ranging from toys and games for consumers, to personalized health equipment such as hearing aids, through to highly specialized parts to be used in aircraft. Its variety of uses also means that the potential impact on existing intellectual property laws is difficult to predict.

For example, what would be the copyright implications be if an individual modified an existing design file or scanned an existing object to create a new design file? Can computer-aided design (CAD) files be protected under copyright law? What are the implications of modifying someone else’s CAD file? For businesses, copyright issues could arise when replacement parts are produced, perhaps through a third-party supplier.

“Our research showed that for consumers, the key issue is providing better guidance about the copyright status of CAD files,” explains Dr. Mendis. “While online platforms for sharing 3D printing design files are still quite niche, interest in them and activity is increasing year-on-year. For businesses, the implications are unlikely to be felt immediately because the cost of printing replica parts is still relatively high. However, as the technology grows and becomes more widely used – particularly in the automotive industry – its effects need to be monitored and measured.”

As 3D printing becomes more popular and more accessible to the average consumer, the key issue for businesses will be ensuring that their products are readily available through legal channels. While it will be some time before 3D printing becomes as widely available, precedents from music and film sharing platforms suggest that the more accessible content is made for consumers, the less likely they are to resort to illegal downloads. By being conscious of these trends and building business models which take into account past precedents, the development of 3D printing as a consumer technology could avoid potential difficulties in the area of intellectual property rights law.

Source: Bournemouth University

Canada’s ‘Age’ of Technology Disruption ~ Eh?

Prepare for Canada’s disruption storm | Deloitte Canada

www2.deloitte.com•Rapid advances in technology are about to disrupt Canada’s business landscape. Robots, 3D printing, artificial intelligence, crowds, clouds and the Internet of Things will profoundly change our … (“Oh Canada ~ Eh!?”)

Read All About It Here:

Preparing for Canada’s Disruptive Storm

Genesis Nanotechnology, Inc. ~ “Great Things from Small Things”

3-D printed guides can help restore function in damaged nerves

Scientists at the Univ. of Sheffield have succeeded in using a 3-D printed guide to help nerves damaged in traumatic incidents repair themselves.

The team used the device to repair nerve damage in animal models and say the method could help treat many types of traumatic injury.

The device, called a nerve guidance conduit (NGC), is a framework of tiny tubes, which guide the damaged nerve ends towards each other so that they can repair naturally.

Patients with nerve injuries can suffer complete loss of sensation in the damaged area, which can be extremely debilitating. Current methods of repairing nerve damage require surgery to suture or graft the nerve endings, a practice which often yields imperfect results.

Although some NGCs are currently used in surgery, they can only be made using a limited range of materials and designs, making them suitable only for certain types of injury.

The technique, developed in Sheffield’s Faculty of Engineering, uses computer aided design (CAD) to design the devices, which are then fabricated using laser direct writing, a form of 3-D printing. The advantage of this is that it can be adapted for any type of nerve damage or even tailored to an individual patient.

Researchers used the 3-D printed guides to repair nerve injuries using a novel mouse model developed in Sheffield’s Faculty of Medicine, Dentistry and Health to measure nerve regrowth. They were able to demonstrate successful repair over an injury gap of 3 mm, in a 21-day period.

“The advantage of 3-D printing is that NGCs can be made to the precise shapes required by clinicians,” says John Haycock, professor of bioengineering at Sheffield. “We’ve shown that this works in animal models, so the next step is to take this technique towards the clinic”.

The Sheffield team used a material called polyethylene glycol, which is already cleared for clinical use and is also suitable for use in 3-D printing. “Further work is already underway to investigate device manufacture using biodegradable materials, and also making devices that can work across larger injuries,” says Dr. Frederik Claeyssens, senior lecturer in biomaterials at Sheffield.

“Now we need to confirm that the devices work over larger gaps and address the regulatory requirements,” says Fiona Boissonade, professor of neuroscience at Sheffield.

Source: Univ. of Sheffield

MIT: New Ultrastiff, Ultralight Material Developed

Nanostructured material based on repeating microscopic units has record-breaking stiffness at low density.

David L. Chandler | MIT News Office

What’s the difference between the Eiffel Tower and the Washington Monument?

Both structures soar to impressive heights, and each was the world’s tallest building when completed. But the Washington Monument is a massive stone structure, while the Eiffel Tower achieves similar strength using a lattice of steel beams and struts that is mostly open air, gaining its strength from the geometric arrangement of those elements.

Now engineers at MIT and Lawrence Livermore National Laboratory (LLNL) have devised a way to translate that airy, yet remarkably strong, structure down to the microscale — designing a system that could be fabricated from a variety of materials, such as metals or polymers, and that may set new records for stiffness for a given weight.

The new design is described in the journal Science by MIT’s Nicholas Fang; former postdoc Howon Lee, now an assistant professor at Rutgers University; visiting research fellow Qi “Kevin” Ge; LLNL’s Christopher Spadaccini and Xiaoyu “Rayne” Zheng; and eight others.

The design is based on the use of microlattices with nanoscale features, combining great stiffness and strength with ultralow density, the authors say. The actual production of such materials is made possible by a high-precision 3-D printing process called projection microstereolithography, as a result of the joint research collaboration between the Fang and Spadaccini groups since 2008.

Normally, Fang explains, stiffness and strength declines with the density of any material; that’s why when bone density decreases, fractures become more likely. But using the right mathematically determined structures to distribute and direct the loads — the way the arrangement of vertical, horizontal, and diagonal beams do in a structure like the Eiffel Tower — the lighter structure can maintain its strength.

A pleasant surprise

The geometric basis for such microstructures was determined more than a decade ago, Fang says, but it took years to transfer that mathematical understanding “to something we can print, using a digital projection — to convert this solid model on paper to something we can hold in our hand.” The result was “a pleasant surprise to us,” he adds, performing even better than anticipated.

“We found that for a material as light and sparse as aerogel [a kind of glass foam], we see a mechanical stiffness that’s comparable to that of solid rubber, and 400 times stronger than a counterpart of similar density. Such samples can easily withstand a load of more than 160,000 times their own weight,” says Fang, the Brit and Alex d’Arbeloff Career Development Associate Professor in Engineering Design. So far, the researchers at MIT and LLNL have tested the process using three engineering materials — metal, ceramic, and polymer — and all showed the same properties of being stiff at light weight.

“This material is among the lightest in the world,” LLNL’s Spadaccini says. “However, because of its microarchitected layout, it performs with four orders of magnitude higher stiffness than unstructured materials, like aerogels, at a comparable density.”

Light material, heavy loads

This approach could be useful anywhere there’s a need for a combination of high stiffness (for load bearing), high strength, and light weight — such as in structures to be deployed in space, where every bit of weight adds significantly to the cost of launch. But Fang says there may also be applications at smaller scale, such as in batteries for portable devices, where reduced weight is also highly desirable.

Another property of these materials is that they conduct sound and elastic waves very uniformly, meaning they could lead to new acoustic metamaterials, Fang says, that could help control how waves bend over a curved surface.

Others have suggested similar structural principles over the years, such as a proposal last year by researchers at MIT’s Center for Bits and Atoms (CBA) for materials that could be cut out as flat panels and assembled into tiny unit cells to make larger structures. But that concept would require assembly by robotic systems that have yet to be developed, says Fang, who has discussed this work with CBA researchers. This technique, he says, uses 3-D printing technology that can be implemented now.

Martin Wegener, a professor of mechanical engineering at Karlsruhe Institute of Technology in Germany who was not involved in this research, says, “Achieving metamaterials that are ultralight in weight, yet stiffer than you would expect from usual scaling laws for elastic solids, is of obvious technological interest. The paper makes an interesting contribution in this direction.”

The work was supported by the U.S. Defense Advanced Research Projects Agency and LLNL.