Posts Tagged ‘Engineering’

The mathematically designed, 3D-printed acoustic metamaterial is shaped in such a way that it sends incoming sounds back to where they came from, Ghaffarivardavagh and Zhang say. Inside the outer ring, a helical pattern interferes with sounds, blocking them from transmitting through the open center while preserving air’s ability to flow through.

Boston University researchers, Xin Zhang, a professor at the College of Engineering, and Reza Ghaffarivardavagh, a Ph.D. student in the Department of Mechanical Engineering, released a paper in Physical Review B demonstrating it’s possible to silence noise using an open, ringlike structure, created to mathematically perfect specifications, for cutting out sounds while maintaining airflow.

“Today’s sound barriers are literally thick heavy walls,” says Ghaffarivardavagh. Although noise-mitigating barricades, called sound baffles, can help drown out the whoosh of rush hour traffic or contain the symphony of music within concert hall walls, they are a clunky approach not well suited to situations where airflow is also critical. Imagine barricading a jet engine’s exhaust vent — the plane would never leave the ground. Instead, workers on the tarmac wear earplugs to protect their hearing from the deafening roar.

Ghaffarivardavagh and Zhang let mathematics — a shared passion that has buoyed both of their engineering careers and made them well-suited research partners — guide them toward a workable design for what the acoustic metamaterial would look like.

They calculated the dimensions and specifications that the metamaterial would need to have in order to interfere with the transmitted sound waves, preventing sound — but not air — from being radiated through the open structure. The basic premise is that the metamaterial needs to be shaped in such a way that it sends incoming sounds back to where they came from, they say.

As a test case, they decided to create a structure that could silence sound from a loudspeaker. Based on their calculations, they modeled the physical dimensions that would most effectively silence noises. Bringing those models to life, they used 3D printing to materialize an open, noise-canceling structure made of plastic.

Trying it out in the lab, the researchers sealed the loudspeaker into one end of a PVC pipe. On the other end, the tailor-made acoustic metamaterial was fastened into the opening. With the hit of the play button, the experimental loudspeaker set-up came oh-so-quietly to life in the lab. Standing in the room, based on your sense of hearing alone, you’d never know that the loudspeaker was blasting an irritatingly high-pitched note. If, however, you peered into the PVC pipe, you would see the loudspeaker’s subwoofers thrumming away.

The metamaterial, ringing around the internal perimeter of the pipe’s mouth, worked like a mute button incarnate until the moment when Ghaffarivardavagh reached down and pulled it free. The lab suddenly echoed with the screeching of the loudspeaker’s tune.

“The moment we first placed and removed the silencer…was literally night and day,” says Jacob Nikolajczyk, who in addition to being a study co author and former undergraduate researcher in Zhang’s lab is a passionate vocal performer. “We had been seeing these sorts of results in our computer modeling for months — but it is one thing to see modeled sound pressure levels on a computer, and another to hear its impact yourself.”

By comparing sound levels with and without the metamaterial fastened in place, the team found that they could silence nearly all — 94 percent to be exact — of the noise, making the sounds emanating from the loudspeaker imperceptible to the human ear.

Now that their prototype has proved so effective, the researchers have some big ideas about how their acoustic-silencing metamaterial could go to work making the real world quieter.

“Drones are a very hot topic,” Zhang says. Companies like Amazon are interested in using drones to deliver goods, she says, and “people are complaining about the potential noise.”

“The culprit is the upward-moving fan motion,” Ghaffarivardavagh says. “If we can put sound-silencing open structures beneath the drone fans, we can cancel out the sound radiating toward the ground.”

Closer to home — or the office — fans and HVAC systems could benefit from acoustic metamaterials that render them silent yet still enable hot or cold air to be circulated unencumbered throughout a building.

Ghaffarivardavagh and Zhang also point to the unsightliness of the sound barriers used today to reduce noise pollution from traffic and see room for an aesthetic upgrade. “Our structure is super lightweight, open, and beautiful. Each piece could be used as a tile or brick to scale up and build a sound-canceling, permeable wall,” they say.

The shape of acoustic-silencing metamaterials, based on their method, is also completely customizable, Ghaffarivardavagh says. The outer part doesn’t need to be a round ring shape in order to function.

“We can design the outer shape as a cube or hexagon, anything really,” he says. “When we want to create a wall, we will go to a hexagonal shape” that can fit together like an open-air honeycomb structure.

Such walls could help contain many types of noises. Even those from the intense vibrations of an MRI machine, Zhang says.

According to Stephan Anderson, a professor of radiology at BU School of Medicine and a coauthor of the study, the acoustic metamaterial could potentially be scaled “to fit inside the central bore of an MRI machine,” shielding patients from the sound during the imaging process.

Zhang says the possibilities are endless, since the noise mitigation method can be customized to suit nearly any environment: “The idea is that we can now mathematically design an object that can block the sounds of anything,” she says.


Researchers at the University of Minnesota use a customized 3D printer to print electronics on a real hand. Image: McAlpine group, University of Minnesota

Soldiers are commonly thrust into situations where the danger is the unknown: Where is the enemy, how many are there, what weaponry is being used? The military already uses a mix of technology to help answer those questions quickly, and another may be on its way. Researchers at the University of Minnesota have developed a low-cost 3D printer that prints sensors and electronics directly on skin. The development could allow soldiers to directly print temporary, disposable sensors on their hands to detect such things as chemical or biological agents in the field.

The technology also could be used in medicine. The Minnesota researchers successfully used bioink with the device to print cells directly on the wounds of a mouse. Researchers believe it could eventually provide new methods of faster and more efficient treatment, or direct printing of grafts for skin wounds or conditions.

“The concept was to go beyond smart materials, to integrate them directly on to skin,” says Michael McAlpine, professor of mechanical engineering whose research group focuses on 3D printing functional materials and devices. “It is a biological merger with electronics. We wanted to push the limits of what a 3D printer can do.”

McAlpine calls it a very simple idea, “One of those ideas so simple, it turns out no one has done it.”

Others have used 3D printers to print electronics and biological cells. But printing on skin presented a few challenges. No matter how hard a person tries to remain still, there always will be some movement during the printing process. “If you put a hand under the printer, it is going to move,” he says.

To adjust for that, the printer the Minnesota team developed uses a machine vision algorithm written by Ph.D. student Zhijie Zhu to track the motion of the hand in real time while printing. Temporary markers are placed on the skin, which then is scanned. The printer tracks the hand using the markers and adjusts in real time to any movement. That allows the printed electronics to maintain a circuit shape. The printed device can be peeled off the skin when it is no longer needed.

The team also needed to develop a special ink that could not only be conductive but print and cure at room temperature. Standard 3D printing inks cure at high temperatures of 212 °F and would burn skin.

In a paper recently published in Advanced Materals, the team identified three criteria for conductive inks: The viscosity of the ink should be tunable while maintaining self-supporting structures; the ink solvent should evaporate quickly so the device becomes functional on the same timescale as the printing process; and the printed electrodes should become highly conductive under ambient conditions.

The solution was an ink using silver flakes to provide conductivity rather than particles more commonly used in other applications. Fibers were found to be too large, and cure at high temperatures. The flakes are aligned by their shear forces during printing, and the addition of ethanol to the mix increases speed of evaporation, allowing the ink to cure quickly at room temperature.

“Printing electronics directly on skin would have been a breakthrough in itself, but when you add all of these other components, this is big,” McAlpine says.

The printer is portable, lightweight and cost less than $400. It consists of a delta robot, monitor cameras for long-distance observation of printing states and tracking cameras mounted for precise localization of the surface. The team added a syringe-type nozzle to squeeze and deliver the ink

Furthering the printer’s versatility, McAlpine’s team worked with staff from the university’s medical school and hospital to print skin cells directly on a skin wound of a mouse. The mouse was anesthetized, but still moved slightly during the procedure, he says. The initial success makes the team optimistic that it could open up a new method of treating skin diseases.

“Think about what the applications could be,” McAlpine says. “A soldier in the field could take the printer out of a pack and print a solar panel. On the cellular side, you could bring a printer to the site of an accident and print cells directly on wounds, speeding the treatment. Eventually, you may be able to print biomedical devices within the body.”

In its paper, the team suggests that devices can be “autonomously fabricated without the need for microfabrication facilities in freeform geometries that are actively adaptive to target surfaces in real time, driven by advances in multifunctional 3D printing technologies.”

Besides the ability to print directly on skin, McAlpine says the work may offer advantages over other skin electronic devices. For example, soft, thin, stretchable patches that stick to the skin have been fitted with off-the-shelf chip-based electronics for monitoring a patient’s health. They stick to skin like a temporary tattoo and send updates wirelessly to a computer.

“The advantage of our approach is that you don’t have to start with electronic wafers made in a clean room,” McAlpine says. “This is a completely new paradigm for printing electronics using 3D printing.”

By Vanessa Bates Ramirez

3D printing is being used to produce more and more novel items: tools, art, even rudimentary human organs. What all those items have in common, though, is that they’re small. The next phase of 3D printing is to move on to things that are big. Really big. Like, as big as a house.

In a small town in western Russia called Stupino, a 3D printed house just went up in the middle of winter and in a day’s time.

Pieces of houses and bridges have been 3D printed in warehouses or labs then transported to their permanent locations to be assembled, but the Stupino house was printed entirely on-site by a company called Apis Cor. They used a crane-sized, mobile 3D printer and a specially-developed mortar mix and covered the whole operation with a heated tent.

The 38-square-meter (409-square-foot) house is circular, with three right-angled protrusions allowing for additional space and division of the area inside. Counter-intuitively, the house’s roof is completely flat. Russia’s not known for mild, snow-free winters. Made of welded polymer membranes and insulated with solid plates, the roof was designed to withstand heavy snow loads.

Apis Cor teamed up with partners for the house’s finishing details, like insulation, windows, and paint. Samsung even provided high-tech appliances and a TV with a concave-curved screen to match the curve of the interior wall.

According to the company, the house’s total building cost came to $10,134, or approximately $275 per square meter, which equates to about $25 per square foot. A recent estimate put the average cost of building a 2,000 square foot home in the US at about $150 per square foot.

The homes of the future?

Since these houses are affordable and fast to build, is it only a matter of time before we’re all living in 3D printed concrete circles?

Probably not—or, at least, not until whole apartment buildings can be 3D printed. The Stupino house would be harder (though not impossible) to plop down in the middle of a city than in the Russian countryside.

While cities like Dubai are aiming to build more 3D printed houses, what many have envisioned for the homes of the future are environmentally-friendly, data-integrated ‘smart buildings,’ often clad with solar panels and including floors designated for growing food.

Large-scale 3D printing does have some very practical applications, though. Take disaster relief: when a hurricane or earthquake destroys infrastructure and leaves thousands of people without shelter, 3D printers like Apis Cor’s could be used to quickly rebuild bridges, roads, and homes.

Also, given their low cost and high speed, 3D printed houses could become a practical option for subsidized housing projects.

In the US, tiny houses have been all the rage among millennials lately—what if that tiny house could be custom-printed to your specifications in less than a week, and it cost even less than you’d budgeted?

Since software and machines are doing most of the work, there’s less margin for human error—gone are the days of “the subcontractor misread the blueprint, and now we have three closets and no bathrooms!”

While houses made by robots are good news for people looking to buy a basic, low-cost house, they could be bad news for people employed in the construction industry. Machines have been pouring concrete for decades, but technologies like Apis Cor’s giant printer will take a few more human workers out of the equation.

Nonetheless, the company states that part of their mission is “to change the construction industry so that millions of people will have an opportunity to improve their living conditions.”

by Matt Hickman

When Tesla, the Silicon Valley automaker and energy storage firm founded by billionaire and Mars colonization enthusiast Elon Musk, unveiled its gorgeous solar roofing system back in October, it was assumed that said shingles would be significantly spendier than conventional roofing — you know, roofing that isn’t capable of transforming free and abundant sunshine into a form of home-powering renewable energy.

After all, why would a roof that’s more durable, longer-lasting and flat-out sexier also be comparable in price — or, gasp, even more affordable — than a traditional asphalt roof?

Weeks later, Musk, a clean tech entrepreneur never without a few surprises up his sleeve, is claiming that Tesla’s sleek solar roofing option will indeed be the cheaper option even before the annual energy savings associated with having an electricity-producing roof kick in.

Made from tempered glass, Tesla’s low-cost solar roofing shingles are slated for a widespread rollout at the end of 2017.

Musk made the potentially too-good-to-be-true claim directly following last week’s announcement that Tesla shareholders had voted to merge with SolarCity, the residential solar behemoth founded by Musk’s cousin Lyndon Rive. (Musk himself serves as chairman of SolarCity, which will now operate as a wholly owned subsidiary of Tesla).

As noted by Bloomberg, the $2 billion acquisition aims to position Tesla, primarily known to most consumers as a manufacturer of beautiful yet prohibitively pricey electric sports cars and sedans, as “one-stop shopping for consumers eager to become independent of fossil fuels.” In the near future, Tesla showrooms won’t just be places to buy and/or ogle high-end EVs. They’ll also be places where consumers can peruse solar roofing options that will help to power their homes and, of course, that Tesla Model S parked in the garage.

Noting that the tiles’ electricity-producing capabilities are “just a bonus,” Musk goes on to pose the question: “So the basic proposition will be: Would you like a roof that looks better than a normal roof, lasts twice as long, costs less and — by the way — generates electricity? Why would you get anything else?”

To be available in a quartet of styles — Slate, Tuscan, Textured Glass and Smooth Glass — that closely mimic not-so-cheap premium roofing materials, Tesla’s solar shingles are a boon for consumers who have long balked at the thought of installing rooftop solar for aesthetic reasons. (Read: big black patches that invoke the ire of the neighbors). Tesla’s shingles look just like the real deal — even nicer. “The key is to make solar look good,” said Musk during last month’s public debut of Tesla’s solar shingles, which you can watch below in its entirety. “We want you to call your neighbors over and say, ‘Check out this sweet roof.’” You can hear his pitch in more detail in the video below:

As reported by Bloomberg, while Tesla’s inoffensive-looking solar shingles are indeed considered a premium product when compared to non-solar shingles, significant savings kick in when considering the cost of shipping. Traditional roofing tiles are heavy and awkward and, as a result, cost an arm and a leg to transport. They’re also super-fragile and have a high rate of breakage. Tesla’s engineered glass shingles, on the other hand, are durable, lightweight (as much as five times lighter than conventional roofing materials) and easy to ship. The significant cost-savings associated with decreased shipping costs, as anticipated by Musk, will be passed on to consumers.

While there are skeptics who doubt that the savings gained in decreased shipping costs will render Tesla’s solar singles the most affordable option for upfront cost-focused consumers, others are embracing Musk’s claims as a potential game-changer that could potentially usher in the end of “dumb” roofing as we know it.

Dubai launches world’s first “functional” 3D printed office building. 3D Printed Building Of 250 square meter structure, Comprises Of A Single Floor With All amenities was printed in 17 days, and assembled in just two days.