MIT Researchers Create Perfect Nanoscrolls from Graphene Oxide

Source: Jennifer Chu, MIT News

An electron microscopy image shows many examples of nanoscrolls. The insert zooms in on a single nanoscroll and reveals its conical nature.

Using both low- and high-frequency ultrasonic techniques, scientists have fabricated nanoscrolls made from graphene oxide flakes.

Water filters of the future may be made from billions of tiny, graphene-based nanoscrolls. Each scroll, made by rolling up a single, atom-thick layer of graphene, could be tailored to trap specific molecules and pollutants in its tightly wound folds. Billions of these scrolls, stacked layer by layer, may produce a lightweight, durable, and highly selective water purification membrane.

But there’s a catch: Graphene does not come cheap. The material’s exceptional mechanical and chemical properties are due to its very regular, hexagonal structure, which resembles microscopic chicken wire. Scientists take great pains in keeping graphene in its pure, unblemished form, using processes that are expensive and time-consuming, and that severely limit graphene’s practical uses.

Seeking an alternative, a team from MIT and Harvard University is looking to graphene oxide — graphene’s much cheaper, imperfect form. Graphene oxide is graphene that is also covered with oxygen and hydrogen groups. The material is essentially what graphene becomes if it’s left to sit out in open air. The team fabricated nanoscrolls made from graphene oxide flakes and was able to control the dimensions of each nanoscroll, using both low- and high-frequency ultrasonic techniques. The scrolls have mechanical properties that are similar to graphene, and they can be made at a fraction of the cost, the researchers say.

“If you really want to make an engineering structure, at this point it’s not practical to use graphene,” says Itai Stein, a graduate student in MIT’s Department of Mechanical Engineering. “Graphene oxide is two to four orders of magnitude cheaper, and with our technique, we can tune the dimensions of these architectures and open a window to industry.”

Stein says graphene oxide nanoscrolls could also be used as ultralight chemical sensors, drug delivery vehicles, and hydrogen storage platforms, in addition to water filters. Stein and Carlo Amadei, a graduate student at Harvard University, have published their results in the journal Nanoscale.

This sketch illustrates how a nanoscroll forms from a graphene oxide flake as a result of ultrasonic irradiation.

Getting away from crumpled graphene

The team’s paper originally grew out of an MIT class, 2.675 (Micro/Nano Engineering), taught by Rohit Karnik, associate professor of mechanical engineering. As part of their final project, Stein and Amadei teamed up to design nanoscrolls from graphene oxide. Amadei, as a member of Professor Chad Vecitis’ lab at Harvard University, had been working with graphene oxide for water purification applications, while Stein was experimenting with carbon nanotubes and other nanoscale architectures, as part of a group led by Brian Wardle, professor of aeronautics and astronautics at MIT.

“Our initial idea was to make nanoscrolls for molecular adsorption,” Amadei says. “Compared to carbon nanotubes, which are closed structures, nanoscrolls are open spirals, so you have all this surface area available to manipulate.”

“And you can tune the separation of a nanoscroll’s layers, and do all sorts of neat things with graphene oxide that you can’t really do with nanotubes and graphene itself,” Stein adds.

When they looked at what had been done previously in this field, the students found that scientists had successfully produced nanoscrolls from graphene, though with very complicated processes to keep the material pure. A few groups had tried doing the same with graphene oxide, but their attempts were literally deflated.

“What was out there in the literature was more like crumpled graphene,” Stein says. “You can’t really see the conical nature. It’s not really clear what was made.”

Collapsing bubbles

Stein and Amadei first used a common technique called the Hummers’ method to separate graphite flakes into individual layers of graphene oxide. They then placed the graphene oxide flakes in solution and stimulated the flakes to curl into scrolls, using two similar approaches: a low-frequency tip-sonicator, and a high-frequency custom reactor.

The tip-sonicator is a probe made of piezoelectric material that shakes at a low, 20Hz frequency when voltage is applied. When placed in a solution, the tip-sonicator produces sound waves that stir up the surroundings, creating bubbles in the solution.

Similarly, the group’s reactor contains a piezoelectric component that is connected to a circuit. As voltage is applied, the reactor shakes — at a higher, 390 Hz frequency compared with the tip-sonicator — creating bubbles in the solution within the reactor.

Stein and Amadei applied both techniques to solutions of graphene oxide flakes and observed similar effects: The bubbles that were created in solution eventually collapsed, releasing energy that caused the flakes to spontaneously curl into scrolls. The researchers found they could tune the dimensions of the scrolls by varying the treatment duration and the frequency of the ultrasonic waves. Higher frequencies and shorter treatments did not lead to significant damage of the graphene oxide flakes and produced larger scrolls, while low frequencies and longer treatment times tended to cleave flakes apart and create smaller scrolls.

While the group’s initial experiments turned a relatively low number of flakes — about 10 percent — into scrolls, Stein says both techniques may be optimized to produce higher yields. If they can be scaled up, he says the techniques can be compatible with existing industrial processes, particularly for water purification.

“If you can make this in large scales and it’s cheap, you could make huge bulk samples of filters and throw them out in the water to remove all sorts of contaminants,” Stein says.

This work was supported, in part, by the Department of Defense through the National Defense Science and Engineering Graduate (NDSEG) fellowship program.

Publication: Carlo A. Amadei, et al., “Fabrication and morphology tuning of graphene oxide nanoscrolls,” Nanoscale, 2016,8, 6783-6791; DOI: 10.1039/C5NR07983G

Engineers Design Calcium-Based Multi-Element for Liquid Batteries

Source: David L. Chandler, MIT News

March 22, 2016

An artist’s rendering of a calcium liquid battery.

In a newly published study, MIT researchers show that calcium can form the basis for both the negative electrode layer and the molten salt that forms the middle layer of the three-layer battery.

Liquid metal batteries, invented by MIT professor Donald Sadoway and his students a decade ago, are a promising candidate for making renewable energy more practical. The batteries, which can store large amounts of energy and thus even out the ups and downs of power production and power use, are in the process of being commercialized by a Cambridge-based startup company, Ambri.

Now, Sadoway and his team have found yet another set of chemical constituents that could make the technology even more practical and affordable, and open up a whole family of potential variations that could make use of local resources.

The latest findings are reported in the journal Nature Communications, in a paper by Sadoway, who is the John F. Elliott Professor of Materials Chemistry, and postdoc Takanari Ouchi, along with Hojong Kim (now a professor at Penn State University) and PhD student Brian Spatocco at MIT. They show that calcium, an abundant and inexpensive element, can form the basis for both the negative electrode layer and the molten salt that forms the middle layer of the three-layer battery.

That was a highly unexpected finding, Sadoway says. Calcium has some properties that made it seem like an especially unlikely candidate to work in this kind of battery. For one thing, calcium easily dissolves in salt, and yet a crucial feature of the liquid battery is that each of its three constituents forms a separate layer, based on the materials’ different densities, much as different liqueurs separate in some novelty cocktails. It’s essential that these layers not mix at their boundaries and maintain their distinct identities.

It was the seeming impossibility of making calcium work in a liquid battery that attracted Ouchi to the problem, he says. “It was the most difficult chemistry” to make work but had potential benefits due to calcium’s low cost as well as its inherent high voltage as a negative electrode. “For me, I’m happiest with whatever is most difficult,” he says — which, Sadoway points out, is a very typical attitude at MIT.

Another problem with calcium is its high melting point, which would have forced the liquid battery to operate at almost 900 degrees Celsius, “which is ridiculous,” Sadoway says. But both of these problems were solvable.

First, the researchers tackled the temperature problem by alloying the calcium with another inexpensive metal, magnesium, which has a much lower melting point. The resulting mix provides a lower operating temperature — about 300 degrees less than that of pure calcium — while still keeping the high-voltage advantage of the calcium.

The other key innovation was in the formulation of the salt used in the battery’s middle layer, called the electrolyte, that charge carriers, or ions, must cross as the battery is used. The migration of those ions is accompanied by an electric current flowing through wires that are connected to the upper and lower molten metal layers, the battery’s electrodes.

The new salt formulation consists of a mix of lithium chloride and calcium chloride, and it turns out that the calcium-magnesium alloy does not dissolve well in this kind of salt, solving the other challenge to the use of calcium.

But solving that problem also led to a big surprise: Normally there is a single “itinerant ion” that passes through the electrolyte in a rechargeable battery, for example, lithium in lithium-ion batteries or sodium in sodium-sulfur. But in this case, the researchers found that multiple ions in the molten-salt electrolyte contribute to the flow, boosting the battery’s overall energy output. That was a totally serendipitous finding that could open up new avenues in battery design, Sadoway says.

And there’s another potential big bonus in this new battery chemistry, Sadoway says. “There’s an irony here. If you’re trying to find high-purity ore bodies, magnesium and calcium are often found together,” he says. It takes great effort and energy to purify one or the other, removing the calcium “contaminant” from the magnesium or vice versa. But since the material that will be needed for the electrode in these batteries is a mixture of the two, it may be possible to save on the initial materials costs by using “lower” grades of the two metals that already contain some of the other.

“There’s a whole level of supply-chain optimization that people haven’t thought about,” he says.

Sadoway and Ouchi stress that these particular chemical combinations are just the tip of the iceberg, which could represent a starting point for new approaches to devising battery formulations. And since all these liquid batteries, including the original liquid battery materials from his lab and those under development at Ambri, would use similar containers, insulating systems, and electronic control systems, the actual internal chemistry of the batteries could continue to evolve over time. They could also adapt to fit local conditions and materials availability while still using mostly the same components.

“The lesson here is to explore different chemistries and be ready for changing market conditions,” Sadoway says. What they have developed “is not a battery; it’s a whole battery field. As time passes, people can explore more parts of the periodic table” to find ever-better formulations, he says.

“This paper brings together innovative engineering advances in cell design and component materials within a strategic framework of ‘cost-based discovery’ that is amenable to the massive scale-up required of grid-scale applications,” says Richard Alkire, a professor of Chemical and Biomolecular Engineering at the University of Illinois, who was not involved in this research.

Because this work builds on a base of well-developed electrochemical systems used for aluminum production, Alkire says, “the path forward to grid-scale applications can therefore take advantage of a large body of existing engineering experience in areas of sustainability, environmental, life cycle, materials, manufacturing cost, and scale-up.”

The research was supported by the U.S. Department of Energy’s Advanced Research Projects Energy (ARPA-E) and by the French energy company Total S.A.

Publication: Takanari Ouchi, et al., “Calcium-based multi-element chemistry for grid-scale electrochemical energy storage,” Nature Communications 7, Article number: 10999; doi:10.1038/ncomms10999

Researchers Combine Excited States of Two Materials into a New Quantum Mechanical State

• Date: March 3, 2014
• Source: University of Michigan
• Image: Tal Galfsky, CUNY

In an optical cavity — a filament lined with mirrors — researchers have used light to bind together quantum mechanical states of two disparate materials. The result could one day enable more robust, efficient solar cells and lighting solutions. Image credit: Tal Galfsky, CUNY

A team of researchers has taken the excited states of two principally different materials and combined them into a new quantum mechanical state that shares their best properties.

Ann Arbor — Like a spring connecting two swings, light can act as photon glue that binds together the quantum mechanical properties of two vastly different materials.

The effect could harness the most useful characteristics from each material for hybrid solar cells and high efficiency lighting, among other applications.

Researchers at the University of Michigan and Queens College, City University of New York, used light to create links between organic and inorganic semiconductors in an optical cavity—a mirror-lined nanoscale filament about 1/1,000th the width of a hair.

Semiconductors are materials whose electrical conductivity can be adjusted by adding impurities, known as dopant atoms. They’re used in all electronic devices, including cell phones and laptops, and also in solar cells and light-emitting diodes.

Organic semiconductors are made of carbon-rich compounds that don’t necessarily come from biological sources, but resemble them. They are newer to the market than their inorganic counterparts such as silicon. But they are finding widespread applications in smart phone displays and room lighting. Organics hold promise to be flexible and inexpensive, perhaps even deployed on large plastic rolls.

“What we’ve done is taken the excited states of two principally different materials and combined them into a new quantum mechanical state that shares their best properties,” said Stephen Forrest, professor of physics and materials science and also the William Gould Dow Collegiate Professor of Electrical Engineering.

This new state demonstrates stronger light absorption and possibly enhanced “nonlinear” optical properties useful in optical switching, said Vinod Menon, associate professor of physics at Queens College.

“Developing engineered nonlinear optical materials with properties that surpass naturally occurring materials is important for developing next generation photonic technologies that rely on the quantum properties of light,” Menon said. “For example, one could develop an optical switch that uses one photon to turn on or off the path of a second photon. This is basically a light switch that regulates light, one photon at a time—an important building block for quantum communication and computing.”

To demonstrate the effect, the researchers started with an inorganic semiconductor—zinc oxide—and made it into nanowires. Then they surrounded it with an organic material—naphthalene tetracarboxylic dianhydride, or NTCDA.

“We chose these two materials because their excited states would be at nearly the same energies. That is, they are in resonance with one another. And we then sandwiched them between two mirrors to form an optical cavity that traps photons, also at the same energy as the excited states,” Forrest said.

“The result was a third, unique quantum state that is a combination of the photon, the excited state of the inorganic semiconductor and the excited state in the organic semiconductor. That sounds hard and it is.”

He likened the construction to two swings connected by a spring. The swings in this case are excitons, or electronically attractive electron-hole pairs. An electron is a negatively charged subatomic particle and a “hole” in this context is the absence of an electron. In a semiconducting material, a hole carries a positive charge.

In the optical cavity, the photon essentially “glues” together all these quantum mechanical states, forming a unique and potentially useful new state called a polariton that can efficiently transfer energy from one material to another, Forrest said.

“In that new state lies their magic,” he said. “Uses in solar energy conversion, light emission and optical switching are just a few examples of applications that can benefit.

The study is titled “Room Temperature Frenkel-Wannier-Mott Hybridization of Degenerate Excitons in a Strongly Coupled Microcavity.” The graduate students who led the experiments are Michael Slootsky, a doctoral student in physics and engineering at U-M, and Xiaoze Liu a doctoral student at CUNY. The paper is published in the current issue of Physical Review Letters. The research is funded by the National Science Foundation Division of Material Research.

Publication: 

Michael Slootsky, et al., “Room Temperature Frenkel-Wannier-Mott Hybridization of Degenerate Excitons in a Strongly Coupled Microcavity,” Phys. Rev. Lett. 112, 076401, 2014; DOI:10.1103/PhysRevLett.112.076401

Engineer models heart valves, wind turbines for better designs, performance

• Date:January 26, 2016
• Source:Iowa State University
• Summary:Computer modeling technologies are being developed to help engineers design better machines. The models are being applied to wind turbines, artificial hearts and gas turbines.

Iowa State's Ming-Chen Hsu is developing a computational toolkit to improve the design, engineering and operation of all kinds of machines.        Credit: Christopher Gannon/Iowa State University

Three thin leaflets blew open and blood blasted through an artificial heart valve, the center stream firing reds and yellows, the colors indicating a flow speed up to 125 centimeters per second. When the leaflets slammed shut, the flow turned to light blue eddies, indicating blood flow had nearly stopped.

And then Ming-Chen Hsu, an Iowa State University assistant professor of mechanical engineering, searched his computer for another video and clicked play.

This time the tip of a wind turbine blade appeared on his monitor, constantly moving, flexing and vibrating as the blade rotated around the rotor hub. Red indicated air moving at a relative speed of 52 meters per second over the top of the blade; blue and green marked the slower air around the blade.

These are computer models featuring technologies called computational mechanics, fluid-structure interaction and isogeometric analysis. They show the flow fields and stresses that mechanical systems have to withstand. And they're part of a toolkit Hsu and his research group are developing to improve the design, engineering and operation of all kinds of machines.

"If we are able to use computers to model and simulate these engineering designs, we can save a lot of time and money," Hsu said. "We don't have to build and test every prototype anymore."

Hsu said it would be impractical, for example, for the wind energy industry to build and test full-scale prototypes of each and every idea for improving the performance of wind turbines.

Instead, the wind energy industry can opt for computational models. Hsu said they're based on complex mathematical equations. They're full of data. And studies show they're accurate.

Using the models, "We can predict the real physics of the problems we are looking at," he said.

And so those videos showing blood flowing through an artificial heart valve or the vibrations of a wind turbine blade are a lot more than colorful graphics. To engineers, they can be as good as full-scale prototypes for studying durability and performance.

Hsu has a background in computational mechanics and started modeling wind turbines during his doctoral studies at the University of California, San Diego. He started modeling heart valves as a postdoctoral research associate at the University of Texas at Austin.

He's been at Iowa State since the fall of 2013 and has built a research group that currently includes doctoral students Austin Herrema, Chenglong Wang, Michael Wu and Fei Xu plus undergraduate student Carolyn Darling. The group is now working on two wind turbine studies and an engine project:

• They're modeling the performance of the "Hexcrete" concrete wind turbine towers being developed by Sri Sritharan, Iowa State's Wilson Engineering Professor in Civil, Construction and Environmental Engineering. The goal is to use prefabricated concrete to build taller wind turbine towers that can access the steadier winds at 120 meters and higher. The project is primarily supported by the U.S. Department of Energy.

• They're also developing software to help engineers design wind turbine blades. The software will bridge a wide gap between blade design tools and performance simulations. The project is supported by a National Science Foundation grant that established Iowa State's graduate program in wind energy science, engineering and policy.

• And Hsu's research group is modeling the performance of the rotors inside gas turbines. The models will help engineers design the next generation of turbine engines. The project is supported by a grant from the U.S. Army Research Office.

Hsu, who teaches courses in fluid mechanics, said the modeling can be applied to all sorts of questions about a machine. In wind turbines, for example, the models can provide answers about material stress and fatigue, rotor aerodynamics, blade design, the wake behind turbines and power efficiency.

"Ten to 15 years ago, computational fluid-structure interaction was new to everyone," Hsu said. "But with the success of this field, more and more methods are being picked up by industry. Our computational methods are improving engineering designs."

Story Source:

The above post is reprinted from materials provided by Iowa State University. Note: Materials may be edited for content and length.

Scientists Develop a Light-Driven Three-Dimensional Plasmonic Nanosystem

This scissor-like nanosystem consisting of bundles of coiled up DNA (grey) measures only a few nanometers. In visible light, the two DNA ends (red) sticking out of the bundles are linked up with each other. When the researchers switch on the UV light, the system opens up. They can measure the opening and closing with the aid of physical changes within the two gold rods (yellow).

Scientists at the Max Planck Institute for Intelligent Systems have developed a nanoplasmonic system in the form of a pair of scissors that they can open using UV light.

Nanomachines could take over a variety of tasks in future. Some day they may be able to perform medical precision work in the human body or help analyze pathogens and pollutants in mobile laboratories. Scientists at the Max Planck Institute for Intelligent Systems in Stuttgart have now presented a possible component which could be used to specifically move and control such a machine. They have developed a nanoplasmonic system in the form of a pair of scissors that they can open using UV light. As soon as they irradiate the nanostructure with visible instead of UV light, it closes again. The researchers can observe the structural changes with the aid of gold particles which they excite with the light.

Animal and plant cells, as well as bacteria store the information about their complete structure and all vital processes in their DNA. In nanotechnology, it is not the ability of DNA to carry the genetic make-up which scientists use, but its elastic structure. This allows them to build components of small machines, such as motors and other tools.

In order to be able to design complete nanomachines, however, scientists must design and further develop possible subunits of a machine step by step. Researchers from the Max Planck Institute for Intelligent Systems together with colleagues from Japan and the USA have now developed a structure made out of DNA that could serve as moving components of a nano-motor or nano-gearbox. Like the two blades of a scissors, they have two DNA bundles connected by a type of hinge. Each bundle is only 80 nanometres long and each consists of 14 strands of coiled up DNA lying parallel to each other. Initially, the motion of the scissor-like nanostructure is blocked by a type of chemical padlock made of azobenzenes, which can be opened by UV light.

The nanoplasmonic system consists of DNA and is closed via visible light. The two DNA bundles (grey) are held together by a small molecular padlock which consists of two protruding DNA ends (red). Embedded in it are azobenzenes which change their structure when excited by UV light (purple). This causes the two DNA bundles to separate from each other and the angle between the two DNA strands opens up. Researchers can detect this structural change using spectra obtained from so-called circular dichroism (CD) spectroscopy (top right), in which changes to the plasmons on the small gold rods (yellow) leave characteristic traces. When the researchers switch off the UV light with the system in the open state and switch on visible light (vis), the azobenzene changes its structure and the two DNA ends link up again.

The chemical padlock is opened by light

The azobenzene components are each connected with a DNA thread that protrudes from each bundle. In visible light, the azobenzene residues assume a structure which allows the protruding DNA strands of the two bundles to link up with each other – the two bundles lie very close to each other. However, as soon as the researchers excite the DNA-azobenzene complex with UV light, the azobenzene changes its structure. This leads to the two loose DNA ends separating and the hinge snapping open within only a few minutes. The light therefore acts, in a sense, like a lubricant for the motion. As soon as the UV light is switched off, the azobenzene changes its structure again, and the two DNA ends link up once more: the nanosystem closes. “When we want to develop a machine, it has to work not only in one direction, it has to be reversible,” says Laura Na Liu, who leads a Research Group at the Max Planck Institute in Stuttgart. The DNA bundles here do not move because the light changes or because the azobenzene changes its structure, but only because of the Brownian molecular motion.

The researchers can observe live how the nanostructure opens and closes. To this end, they have linked up the DNA nanotechnology with so-called nanoplasmonics: a research field that deals with the oscillations of electrons – so-called plasmons – at a metal surface. The plasmons can arise when light impinges on a metal particle, and leave behind a characteristic signature in suitable light.

Tiny gold rods provide information on the opening state

The Research Group led by Laura Na Liu has generated these plasmons on two tiny gold rods, each sitting on one of the two bundles of DNA. Using the analogy of the scissors, these two gold particles each lie on the outer side of a scissor blade and cross over like the DNA bundles at the hinge of the scissors. The light excitation causes not only the molecular padlock fixing the two DNA bundles together to spring open, plasmons on the gold particles also start to oscillate. When the scissor-like structure opens, the angle between the two gold rods changes as well, which has an effect on the plasmons. The researchers can observe these changes spectroscopically by irradiating the nanosystem with light with suitable properties and measuring how it changes. They can thus even determine the angle between the DNA bundles.

“We have succeeded for the first time in controlling a nanoplasmonic system with light. And this was precisely our motivation,” says Laura Na Liu. The researcher and her colleagues had previously worked on nanosystems that can be chemically controlled. However, the chemical controls are not as clean and leave residues in the system.

Laura Na Liu already has an application in mind for the light-controlled scissor design. The system could serve as a tool to control the arrangement of nanoparticles. “As the angle between the two DNA bundles can be controlled, it offers the possibility to change the relative position of nanoparticles in space,” says Laura Na Liu. Moreover, the scientists consider the current work as a step towards a nanomachine. The nanoplasmonic system could be part of such a machine.

Publication: Anton Kuzyk, et al., “A light-driven three-dimensional plasmonic nanosystem that translates molecular motion into reversible chiroptical function,” Nature Communications 7, Article number: 10591; doi:10.1038/ncomms10591

How jogging helps you stay sharp

Exercise can enhance the development of new brain cells that play an important role in learning and memory of adults, new research has found.

The process of developing new brain cells in the adult brain is called adult neurogenesis, the scientists explained.

The researchers found that mice that spent time running on wheels not only developed twice the normal number of new neurons, but also showed an increased ability to distinguish new objects from familiar objects.

“Our research indicates that exercise-induced increase in neurogenesis improves pattern separation by supporting unique and detailed long-term representations of similar but nevertheless different memory items,” explained lead investigator Josef Bischofberger,  professor at University of Basel in Switzerland.

“Pattern separation is involved in many memory tasks of everyday life. For example, when learning the game of chess, it is critically important to remember the different shapes of pieces like the pawn and bishop,” Bischofberger explained.

For the study, the researchers tested two groups of mice that were housed either without (sedentary) or with running wheels (voluntarily running) using a novel object recognition  task to assess learning and long-term memory.

The researchers found that whereas distinct objects were remembered and recognized by both cohorts of mice, only the running mice could faithfully distinguish similar looking objects.

Investigators determined therefore that the running mice had developed better pattern separation capabilities than sedentary mice.

To investigate further, the researchers looked for changes in the brains of the mice. By using markers that could identify newly-formed brain cells, they found that running mice developed about twice as many new cells.

The study was published in the journal of Brain Plasticity. (IANS)

Hydrogel superglue is 90 percent water

New 'water adhesive' is tougher than natural adhesives employed by mussels and barnacles 

Date:November 9, 2015

Source:Massachusetts Institute of Technology

Engineered hydrogel being pulled away from a glass surface. The material shows a property called "tough wet adhesion" comparable to tendon and bone interface. The wavy edge instability at the interface is a hallmark of strongly adhered soft material on a rigid surface.

Credit: Felice Frankel

Nature has developed innovative ways to solve a sticky challenge: Mussels and barnacles stubbornly glue themselves to cliff faces, ship hulls, and even the skin of whales. Likewise, tendons and cartilage stick to bone with incredible robustness, giving animals flexibility and agility.

The natural adhesive in all these cases is hydrogel -- a sticky mix of water and gummy material that creates a tough and durable bond.

Now engineers at MIT have developed a method to make synthetic, sticky hydrogel that is more than 90 percent water. The hydrogel, which is a transparent, rubber-like material, can adhere to surfaces such as glass, silicon, ceramics, aluminum, and titanium with a toughness comparable to the bond between tendon and cartilage on bone.

In experiments to demonstrate its robustness, the researchers applied a small square of their hydrogel between two plates of glass, from which they then suspended a 55-pound weight. They also glued the hydrogel to a silicon wafer, which they then smashed with a hammer. While the silicon shattered, its pieces remained stuck in place.

Such durability makes the hydrogel an ideal candidate for protective coatings on underwater surfaces such as boats and submarines. As the hydrogel is biocompatible, it may also be suitable for a range of health-related applications, such as biomedical coatings for catheters and sensors implanted in the body.

"You can imagine new applications with this very robust, adhesive, yet soft material," says Xuanhe Zhao, the Robert N. Noyce Career Development Associate Professor in MIT's Department of Mechanical Engineering. For example, Zhao's group is currently exploring uses for the hydrogel in soft robotics, where the material may serve as synthetic tendon and cartilage, or in flexible joints.

"It's a pretty tough and adhesive gel that's mostly water," Hyunwoo Yuk, a graduate student in mechanical engineering and the lead author of a paper on the work, says. "Basically, it's tough, bonding water."

Zhao and his students publish their results today in the journal Nature Materials.

A stretchy anchor

A tough, flexible hydrogel that bonds strongly requires two characteristics, Zhao found: energy dissipation and chemical anchorage. A hydrogel that dissipates energy is essentially able to stretch significantly without retaining all the energy used to stretch it. A chemically anchored hydrogel adheres to a surface by covalently bonding its polymer network to that surface.

"Chemical anchorage plus bulk dissipation leads to tough bonding," Zhao says. "Tendons and cartilage harness these, so we're really learning this principle from nature."

In developing the hydrogel, Yuk mixed a solution of water with a dissipative ingredient to create a stretchy, rubbery material. He then placed the hydrogel atop various surfaces, such as aluminum, ceramic, glass, and titanium, each modified with functional silanes -- molecules that created chemical links between each surface and its hydrogel.

The researchers then tested the hydrogel's bond using a standard peeling test, in which they measured the force required to peel the hydrogel from a surface. On average, they found the hydrogel's bond was as tough as 1,000 joules per square meter -- about the same level as tendon and cartilage on bone.

Zhao group compared these results with existing hydrogels, as well as elastomers, tissue adhesives, and nanoparticle gels, and found that the new hydrogel adhesive has both higher water content and a much stronger bonding ability.

"We basically broke a world record in bonding toughness of hydrogels, and it was inspired by nature," Yuk says.

Sticky robotics

In addition to testing the hydrogel's toughness with a hammer and a weight, Zhao and his colleagues explored its use in robotic joints, using small spheres of hydrogel to connect short pipes to simulate robotic limbs.

"Hydrogels can act as actuators," Zhao says. "Instead of using conventional hinges, you can use this soft material with strong bonding to rigid materials, and it can give a robot many more degrees of freedom."

The researchers also looked into its application as an electrical conductor. Yuk and other students added salts to a hydrogel sample, and attached the hydrogel to two metal plates connected via electrodes to an LED light. They found that the hydrogel enabled the flow of salt ions within the electrical loop, ultimately lighting up the LED.

"We create extremely robust interfaces for hydrogel-metal hybrid conductors," Yuk adds.

Zhao's group is currently most interested in exploring the hydrogel's use in soft robotics, as well as in bioelectronics.

"Since the hydrogel contains over 90 percent water, the bonding may be regarded as a water adhesive, which is tougher than natural glues, such as in barnacles and mussels, and bio-inspired underwater glues," Zhao says. "The work has significant implications in understanding bio-adhesion, as well as practical applications such as in hydrogel coatings, biomedical devices, tissue engineering, water treatment, and underwater glues."

This research was supported in part by the Office of Naval Research and the National Science Foundation

Lexus Hoverboard Proves the Future is the Present

Issue: August 2015

Author(s): John Hitch

https://youtu.be/ZwSwZ2Y0Ops

Lexus has dreamed the impossible dream, and after decades of rumors and hoaxes, the hoverboard is now a real thing. It may be the coolest, but certainly not the first eccentric idea to escape the 1980s.

The present is mere months away from becoming the future Marty McFly visited in "Back to the Future II." Oct. 21, 2015, to be exact. Just in time for the momentous event no one will care about on Oct. 22, Lexus has released evidence of a working hoverboard.

For as bad as "The Transformers" movies have been, this has restored my faith in the corporations exploitation of '80s nostalgia.

Cynics may point out that the 25-lb bamboo board only works in one custom-made "hoverpark" in Barcelona, which is embedded with magnets. Or that the liquid nitrogen that cools the superconducting blocks to achieve the magnetic levitation effect must be constantly replenished Or that it’s just a very expensive PR stunt and unfortunately not a real available to the public.

Cynicism is understandable in a lot of areas of our society -- especially in the technology sector-- but it has no place here. What the Lexus team, along with scientists at IFW Dresden and and evico GmbH, achieved in 18 months is amazing.

Think about it. Since children first heard the word hoverboard, whispers of its actual existence have delicately floated across playground asphalt the world over. Even last year, skateboarding icon Tony Hawk stirred up the man-child demographic by appearing on the mythical machine, though thatturned out to be a hoax from Funny or Die.  Now, modern engineering has made it a reality.

According to Rob Holland of Jalopnik.com, who got to take a test spin, the board works as promised.

“The closest feeling that comes to it is ice skating, but even that’s like comparing the finest silk to 300 grit sandpaper,” he wrote.

The hoverboard isn’t the first outlandish future tech from the movie to make it into our everyday lives. There’s an article from Newsweek.com that goes over all the other technological advances predicted or inspired just by "Back to the Future II," including smart glasses, large screen displays and biometrics.

Popular culture from the ’80s, specifically 1985, hit on a surprising number of predictions about the present day. Here are four more:

Drone technology, "Ender’s Game"

Ender’s Game author Orson Scott Card had the foresight to think up several technologies that operated like the Internet and iPads. The story's major twist revolves around the use of drone technology in a war against alien bugs, although this may be something he was warning us about.

Now, remote operators routinely use Predator drones to perform military strikes. Though out of harm’s way, like in "Ender’s Game," intelligence analysts still feel the psychological effects long after.

“I may not have been on the ground in Afghanistan, but I watched parts of the conflict in great detail on a screen for days on end. I know the feeling you experience when you see someone die. Horrifying barely covers it,” former DGS-1 analyst Heather Linebaugh wrote in The Guardian.

Biogas Plants, "Mad Max: Beyond Thunderdome"

Gasoline was in short supply in this post-apocalyptic future, estimated to be between 2014-2018. The Road Warrior found himself stuck in the city of Barter, which generated its power from methane, the byproduct of the anaerobic digestion of pig waste. The series was also recycled in this year’s "Mad Max: Fury Road."

For years, several factories across the world now employ biogas plants in their sustainability efforts.Germany even has an incentive program to increase biogas to phase out nuclear power by 2022.

Holograms, "Jem and the Holograms"

With the help of a hologram-generating computer, mild mannered Jerrica Benton transforms into Jem, who fronts a band and fights other singers, sort of like Taylor Swift.

In one of the larger scale uses of holograms, GE employs the light constructs to simulate future wind farms to allow engineers to tweak and optimize the height and placement of the wind turbines, as well as blade shape. This practice has reportedly made the capturing wind power 20% more effective.

Awkward Android, "Small Wonder"

Thankfully, the one on this list that hasn’t been made into a movie. In this show that somehow lasted four years, a robotics engineer brings home his pint-sized creation to adapt to humans. In typical '80s sitcom fashion, hilarity does not ensue.

The creators of Atlas, the DARPA-funded robot made by Boston Dynamics, may be a bit more clumsy, but infinitely more entertaining. Atlas is also 6'2, 345 lb, so laughing isn't recommended in its general vicinity.

CO₂: Clean for Cooling and Cool for Cleaning

Clean for Cooling

Liquid coolants have many benefits in machining, but they fall short when a work piece must remain dry. Machinists have tried to get around this problem by using cold air guns, but this dry method doesn’t lower temperatures quickly enough. Enter CO₂ as a viable alternative coolant.

CO₂ cooling delivers solid crystals of dry ice into the heat zone, where the tool and work piece meet, at a temperature of -110°F. The dry ice penetrates the vapor-heat barrier to improve heat transfer. This cooling effect keeps the cutting edge sharper and extends the tool’s life compared to conventional dry or minimum quantity lubrication processes. CO₂ coolant can be delivered in two ways: For drilling, it is delivered through ports in the tool. For milling and other machining processes, an external delivery is utilized.

Solid particles of CO₂, or dry ice, exit through the ports in the spindle used in a drilling operation to keep the tool cool and extend its overall life. CO₂ does not require special tooling and is compatible with any standard drill bit.

In the aerospace and automotive industries, manufacturers who work with composites opt away from using conventional liquid fluid coolant. Composite have a porous surface which can trap coolant and requires an extensive cleaning procedure. Drilling composites dry eliminates the necessary cleaning, which is why using dry CO₂ cooling is acceptable—e.g., it cools without leaving behind any trace residue.

This process works well with stack ups. Using the example of a composite titanium stack up, a drill penetrates easily through the composite without creating much heat. Once it hits a titanium layer, however, the drill meets resistance and generates a significant amount of heat. The concern for manufacturers is that this heat buildup greatly diminishes tool life. In addition, metal chips exiting can damage the composite layer, resulting in poor hole tolerances and delamination.

A side view of the stack up shows a composite on top of titanium. As the drill goes deeper in the stack up, an increase in heat is shown in red. Without proper cooling, the heated tool and chips can cause the composite’s properties to become jeopardized.

CO₂ technology addresses both of these issues. First, the CO₂ moves through the drill, maintaining an ambient temperature. As the drill continues to move through the layers, it cools the hole—making it harder, and significantly reducing the damage done by the metal chips. Plus, the process remains completely dry while allowing tighter hole tolerances and increases in tool life.

Cool for Cleaning

CO₂ is also finding use as a cleaning agent. In the automotive industry, several major car makers have found that CO₂ cleaning saves them money and time while lowering their negative impact on the environment.

CO₂ is used for pretreatment of plastics; it can clean parts such as automotive trim, door handles, dashboards, and headlights, prior to a painting or coating. CO₂ spray effectively removes all contaminants that may affect the quality of the paint, such as light oils, water marks, dusts, and fingerprints.

CO₂ spray cleaning systems are integrated directly into the manufacturing line. The parts heading for the entrance to the painting booth are cleaned with the help of two robots that work simultaneously to remove all the foreign objects on the surface.

CO₂ spray is delivered at pressures high enough to clean parts effectively, but low enough not to damage parts’ surfaces. Unlike traditional cleaning processes, CO₂ evaporates completely, leaving no residue to necessitate a second cleaning. It also cleans without condensation, so there is no need for cleaning zones in most plants. After cleaning with dry CO₂, parts can move directly into painting/coating, saving energy and time associated with expensive drying processes.

Aqueous cleaning has been the norm for industries that relied on traditional methods for cleaning and sterilization. Although cleaning with water has been very successful in many applications, the process is showing drawbacks as newer materials, like porous implants, are adopted. Water-based cleaning uses water and ultrasonics to clean. Water can become trapped in the substrate after cleaning, leaving water spots. When that happens, an additional drying procedure is required. 

Similar to pretreatment plastics cleaning, CO₂ cleans optic lenses of water spots and light particulate without damaging the surface. Other industries include, but not limited to electronics, semiconductor, medical, and aerospace.

Liquid CO₂ (LCO₂) provides a solution where a part is completely immersed and concealed in a highly pressurized vessel at around 600-900 psi. The low viscosity and surface tension of LCO₂ lets it flow easily through porous parts, rinsing away contamination without leaving behind residue.

After pressure is released from the vessel, the CO₂ evaporates and a clean, dry, porous part remains—all in about 20 to 45 minutes. As an added environmental benefit, the CO₂ is recaptured after use, reducing the amount of energy used to recover it.

LCO₂ can also be used to clean materials by extracting unwanted compounds (such as unreacted silicone oils) with minimal damage or denaturing. The biggest advantage of LCO₂ is its low levels of toxicity. LCO₂ cleaning works well on medical implants, catheters, silicone tubing, and silicone disks to outgas. Compared to expensive vacuum bake out systems, LCO₂ takes significantly less time (1 to 6 hours, compared to 24 to 72 hours).

In summation, CO₂ is changing the manufacturing landscape in more ways than one. It’s time to start taking notice.

Welcome to the Industrial Wearable Revolution

While wearable technologies struggle to get footing in the consumer market, the devices are already stirring a full-on technological revolution behind the factory walls.

Author(s): Travis Hessman

Sep. 17, 2015

In the consumer world, we generally think of wearables as something new and exciting—a piece of sci-fi futurism just starting to come to life. It's something to watch, something that could one day be the next be thing.

However, a new report suggests that the wearable revolution is already well underway in the industrial sector. 

According to the report, "State of Enterprise Wearables," a whopping 93% of the large industrial companies surveyed in the study indicated that they are already either evaluating or using some kind of wearable device today. 

That kind of ubiquitous support and interest is unprecedented, especially for such a nascent industry. 

APX Labs

"We are experiencing an invisible revolution," says Brian Ballard, CEO and co-founder of APX Labs – the Virginia-based wearable software provider that commissioned the study.

While the consumer world is just now beginning to embrace wearables in our everyday lives, he explains, in the manufacturing world these smart watches and glasses, these wearable scanners and cameras are already being deployed at a furious rate. 

"Almost all of this is happening underneath the factory floor—it's happening out in field service companies," he says. "It's not something you just pick up at Best Buy; it's work first." 

Consumer vs Industry

The main difference between these two markets, it seems, is basic utility. Out in the consumer world, Google Glasses and Apple Watches are basically just nifty gadgets that help us stay connected. But on the plant floor, they can be powerful manufacturing tools. 

Of the 201 companies surveyed for the APX Labs report, 90% said they believe wearables will provide "significant benefits in reducing time, effort, and re-work while also improving quality, safety, and process flexibility."

Backing that up, the report also highlights a Gartner Research study that estimates that smart glasses will yield $1 billion in annual cost savings in the field service industry alone. 

So in this realm, these are hardly just nifty gadgets.

APX Labs

Another big different, Ballard notes, is that, under the factory roof, smart technologies and big data communication is already decades ahead of the outside world.

"The Internet of Things is 20 years old inside industry; it's already well established," he says.

Already today, he explains, factories are equipped with smart machines and communication protocols that offer high data rates communicating over low-cost, hi-fidelity Wi-Fi systems. Companies have already dug deep into big data and big analytics to increase efficiency and intelligence.

"The piece of the equation that has been missing is, once you have machines connected to analytics, how do you move forward into it?" Ballard argues. "Wearable technology is the interface into the connected Internet of Things—it is the most accessible, natural interface that we have today."

Wearable Barriers

This is not to say that dropping wearables into an industrial environment is without complication, though.

APX Labs

Generally, two issues are at the top of the barrier list: Cost and Security.

According to the report, nearly 70% of large companies (5,001+ employees) highlighted security as their top concern. That's not surprising, given the mature – and often complicated – cyber security measures these companies have in place.

The cost issue – again, not surprisingly – was the top concern for mid-sized companies (1,001-5,000 employees) for whom wide deployment of $1,000 glasses of $500 watches can wipe out a big chunk of the budget.

However, the biggest concern not mentioned in the report – but mentioned often among manufacturers – is the fear of so-called "distracted manufacturing."

For many, the idea of setting workers out in a plant filled with heavy equipment, moving machines, and a million hazards with a screen stuck to their faces defies their basic notion of industrial safety.

Ballard, however, is not so concerned.

"We definitely get that quite a bit," he says. "Depending on the customer, there might be a couple of ways to address it."

First, he says, if this is a hard and fast requirement in a factory, companies can simply be sure that the screen is not on while workers are moving. Simple enough.

The other point, he notes, is that "distracted manufacturing" might be a far greater fear than it should be.

"Just think about the amount of activities that people do a day in which their peripheral vision is blocked but they are still able to navigate safely. When you're driving, you're in a car that blocks, frankly, the majority of your peripheral vision," he says. "You still have instrumentation up, your speedometer, your odometer. These are critical tools to your job and they are always a glance away.

"Maybe one way to think of it is smart glasses might be the odometer for your job."

Furthermore, he argues, this concern might be ignoring our natural ability to adapt to these distractions.

"I've played a lot of sports in high school and college that required me to wear a helmet that blocked a good portion of my vision, but I could still play that position incredibly well," he says. "Your body learns to adapt to the equipment that you're wearing."

"And think about fighter pilots," he adds. "They are wearing heads up displays going past the speed of sound in multimillion dollar machines and they have been doing it for over 30 years."

What's Next?

While this report shows a strong movement already underway in the industrial wearable market, there remains a big wave of adoption still waiting to come through. 

"We have 93% penetration in brands using wearables, but we aren't at 93% of user population within these companies yet," Ballard says.

While today actual users wearing these device in the factory or in the field are still a rather small minority, the report indicates that, on average, respondents expect to deploy them to about 45% of their employee base.




"The fact that there are so many companies that have recognized this as an opportunity to connect and entire cross-section of the workforce is fantastic," Ballard says. "But there is still a lot of growth to come."

Increasing Production Uptime and Throughput in Packaging Applications

Author(s): Chris Graff, VP of Sales/Marketing at Butler Automatic Sep. 04, 2015

Downtime, both planned and unplanned, can have pronounced impact on packing line efficiency and throughput. This downtime, caused by film roll changes, registration errors, catastrophic film failures, bottlenecks, and more, is costly, and may seem impossible to avoid. Taking appropriate steps to streamline processes wherever possible can help to mitigate the repercussions of downtime, improving your overall line efficiency and therefore profitability.

Common Causes of Downtime in Packaging Lines

The single greatest cause of downtime in packaging lines according to line efficiency studies is the time it takes to change over rolls of packaging film as they expire. Operators often estimate that each packaging web roll changeover and splice to the previous roll takes about 1-2 minutes, which is itself a great deal of time when the number of roll changes per day are accounted for. These estimates are quite low, however; measured downtime runs closer to an average of 3-5 minutes per roll change. If, in a conservative estimate, a company continuously running a single packaging line must change film rolls ten times per day, the line loses an average of at least 30 minutes of production per day, or more than 8,000 minutes each year. Taking into account a similarly conservative estimate of 80 packages per minute and a $0.50 profit per item, the decreased throughput accounts for hundreds of thousands of dollars in potential profits lost per year.

Other causes of downtime in packaging lines also relate to film splicing. Improperly spliced film, for example, can lead to weak splices and splice failure during production. When the splice separates, or a weak spot in the film itself causes it to fail, the line must be shut down until the web path is rethreaded. This can take anywhere from 20 minutes to an hour in most applications, or two hours or more in aseptic applications where operators must re-sterilize machinery before restarting the line. Most packaging lines experience these kinds of critical failures about once every week.

Poor splices can also lead to registration errors in the film, where the film is improperly aligned and defective packages result. The registration error may result in barcoding issues, faulty seals, and/or package aesthetics that are simply unacceptable for consumer goods. These errors don’t cause downtime, but they can cause a great deal of waste and rework, thereby significantly decreasing line throughput and efficiency.

Bottlenecks are the final main cause of line downtime and inefficiency to be highlighted here. Bottlenecks represent a significant loss of potential throughput, given that the throughput of a packaging line is only maximized when there are no slow spots in the line that have to be compensated for by slowing or stopping the upstream parts of the line. If one stage of a packaging line can handle 1000 packages per minute, but the following stage can only handle 800, packages will accumulate between the two until the maximum accumulation is reached, at which point the first stage will have to be stopped or slowed until the excess packages are processed. Maximized throughput is critical to line efficiency and to maximizing profits, and so identifying and reducing bottlenecks are critical as well.

Key Techniques for Increasing Efficiency

For packaging line operators and managers looking to increase line efficiency and throughput by minimizing downtime, gathering accurate information 

Zero-speed automatic splicers, invented by Butler Automatic, are relatively small capital investments that lead to increased line efficiency and profitability.

about their packaging line is the first step. By committing to the measurement of the numerical performance of the line, operators can fully analyze the performance of the line and note where improvements can occur. Measuring and tracking performance can on its own help to improve performance, especially when people on the factory floor are engaged in the process. Employees who are encouraged to benchmark and objectively analyze their performance, as well as that of the line, become energized to find ways to create efficiencies. In this way, a culture of measuring and gauging emerges, to the benefit of the entire operation.

Measurement is also the best way to find efficiencies where bottlenecks are concerned. With accurate data about processing speeds at each stage and accumulation point sizes, plant operators can determine where bottlenecks occur, and how strategic changes or investments can reduce these bottlenecks and increase throughput.

Beyond measuring, specific changes to manufacturing practices can create efficiencies and increase throughput. Given that three major causes of downtime in packaging lines relate to film splicing, it is clear that utilizing a system that more efficiently carries out high-quality, accurate splices will significantly reduce downtime and increase profitability. Automatic splicing technology, invented by Butler Automatic and in use around the world, addresses these concerns and significantly reduces downtime. With this technology, the amount of time it takes to make a splice is greatly reduced and the accuracy of that splice is improved. Most importantly, however, the machines store a length of packaging film to use during the execution of the splice, so the production line runs continuously during splicing. 

The above example of potential profits lost due to roll change downtime is no longer relevant when roll change downtime is eliminated, and those potential profits can be realized. Catastrophic film failures become much less likely when automatic splicing is used due to the greater accuracy and quality of splices, as do registration errors. In addition, the reduced time spent on each splice often means that fewer operators can manage the task, thereby reducing labor costs. Film waste and the associated cost of lost packages on each roll is also reduced, as the machines are able to automatically sense the expiring roll, which leads to splices far closer to the end of the roll.

Impacts of Efficient Operation

By increasing productivity and efficiency with these above techniques, plant operators are increasing the profitability of the business. When line efficiency is maximized, each package is able to absorb more of the plant overhead. The existing capital structure can be utilized to fulfill more customer orders at what is ultimately a lower unit cost. Relatively small but highly strategic capital investments, such as automatic splicing machines or machinery to eliminate a single bottleneck point in the line, can be returned quickly and ultimately lead to even greater line profitability.