You are browsing the archives of University of Illinois.

Check ‘em out:

US firm uses solar power to recover oil reserves

A new technology to increase oil production is being tested on one of US’s oldest oil fields in one of the largest demonstration projects of its kind. The new project was launched by Chevron Technology Ventures at the Coalinga Field in California. More than 7,600 mirrors are being used to focus the sun’s energy onto a solar boiler to produce steam that can then be injected into oil reservoirs to enhance oil recovery.

UC Merced research team demonstrates nontracking solar concentrator technology to power air-conditioning unit

Professor Roland Winston and his team of student researchers have designed and developed a system that gathers and concentrates sunlight onto specially made collector tubes. The heat generated can then be transformed using existing technology for cooling, heating and a number of other potential uses. The key factor in their design is this: The collectors are entirely stationary. Typically, solar collectors must move and track the sun to achieve optimal energy production, necessitating additional equipment that can be costly to install and complex to maintain.

Global greenhouse gas emissions hit an all-time high in 2010

Global greenhouse gas emissions increased by 5.8% in 2010 to hit an all-time high of 33 billion tonnes, as continued growth in developing countries swamped both greater use of renewable power and gains in energy efficiency, according to an analysis by the European Commission’s Joint Research Centre and the PBL Netherlands Environmental Assessment Agency. Emissions in China and India increased by 10% and 9%, respectively, compared with 3% in the United States.

Molecular sudoku

A team of scientists from the Catalan Institute of Nanotechnology, ICREA, and Universitat Autonoma de Barcelona investigated the properties of a special kind of sudoku, made by assembling tiny molecules into a 3×3 square array The result is not a mind-boggling game, but a detailed picture of how each molecule interacts with its neighbors and conducts electricity when squeezed between two metallic electrodes.

Mirage effect from thermally modulated transparent carbon nanotube sheets (pdf)

The single-beam mirage effect, also known as photothermal deflection, is studied using a free-standing, highly aligned carbon nanotube aerogel sheet as the heat source. The extremely low thermal capacitance and high heat transfer ability of these transparent forest-drawn carbon nanotube sheets enables high frequency modulation of sheet emperature over an enormous temperature range, thereby providing a sharp, rapidly changing gradient of refractive index in the surrounding liquid or gas.

How fuel cells can help cell phones in a hurricane

A cleaner alternative is emerging. Wireless service providers increasingly are investing in fuel cell systems for backup power. Fuel cells use hydrogen and oxygen, the molecules that create water, to produce electricity with no pollution. We see it as a green alternative that is on the rise. Clean and energy efficient fuel cells can help reduce CO₂ emissions by 50 percent as well as decrease other toxic emissions and deliver additional environmental and efficiency benefits. They also are very quiet, less costly to maintain and are not targets for theft.

Pump may help materials self repair

Artificial microvascular systems can be integrated into structures and materials to aid in self-repair when there’s damage, such as cracks in a coating applied to a building or bridge. Until now, the systems have relied on capillary force to transport healing agents. The team of researchers at the Beckman Institute of the University of Illinois has developed different methods for self-healing, including microvascular systems for self-repair of polymers. The vascular system works when reactive fluids are released in response to stress, enabling polymerization that restores mechanical integrity.

Share

Mathematics—the common language of science and engineering—often proves to be the doorway between disciplines. The common ground between a skyscraper, an airplane wing, and facial bones may not seem obvious until one realizes that from a structural perspective, they are all framework systems that must support and transmit loads within certain constraints. By breaking a structure into trusses, nodes, forces, etc., the mathematics transcends the application, and modeling principles can be applied broadly.

A story on the NSF website describes a study that demonstrates the use of topological optimization to “engineer” new faces when facial bones are destroyed by severe injury or disease. The standard surgical approach to craniofacial repair has been to take part of a larger bone from the patient and sculpt it to shape for implantation, an imperfect approach that may leave the patient improved but still significantly deformed.

“The middle of the face is the most complicated part of the human skeleton. What makes the reconstruction more complicated is the fact that the bones are small, delicate, highly specialized and located in a region highly susceptible to contamination by bacteria,” says Glaucio Paulino in the story. Paulino is program director of the mechanics of materials program at the NSF, professor of civil and environmental engineering at the University of Illinois, Urbana-Champaign and one of the PIs on the study.

Topological optimization takes into account limiting factors, such as available space, applied force, load and layout constraints. From the story, “Imagine a building grid in which you can determine where there should be material and where there shouldn’t. Moreover, you can express loads and supports that would affect certain parts of this block of material. Your final result is an optimized structure that fits your established constraints.”

In a PNAS paper (pdf) published in 2010, Paulino and his colleagues from Ohio State University’s School of Medicine demonstrated the feasibility of using the method to custom design a bone replacement for a massive facial injury. In the conclusions of the paper, they also note that the computational algorithms can be expanded to include other critical variables like oxygen levels, surgical flaps, aesthetics and even cost.

(This fascinating 40-second video shows the transformation of a block into a complex upper jaw prosthesis.)

This approach to designing the prosthetic’s structure dovetails very nicely with work already being done in the materials community on additive manufacturing and laser-based manufacturing fabrication of surgical implants.

At the Fraunhofer Institute in Germany, studies are showing that selective laser melting can be used to fabricate a porous polylactide-tricalcium phosphate composite that the body absorbs as natural bone grows into the scaffold. Structures have been assembled that can close openings of up to 25 cm. Selective laser melting is an additive manufacturing process that uses three dimensional CAD renderings to guide a laser beam through a powder bed to melt powders into a dense component.

The Roger Narayan group at the combined UNC-NC State biomedical engineering department is using two-photon polymerization to synthesize polymeric and zirconia shapes for medical applications. Two-photon polymerization uses laser radiation to initiate chemical reactions, polymerization and hardening of a material to build submicrometer structures.

There are commercial examples, too, of rapid prototyping fabrication of customized surgical implants. TMJ Concepts manufactures temporomandibular joint prostheses from titanium using computer numerical control machining based on patient CAT scans.

Share

A group of researchers representing several institutions report in Science they have gained new abilities to “print” graphene oxide-based nano-scale replacements for IC wiring and some semiconductor devices using a method that employs an atomic force microscope to act as a printer head do the detailed work of tuning the conductivity of the material in precise patterns.

GO is an interesting material because it is more resilient to mechanical stresses than standard graphene. Furthermore, in a reduced form, GO becomes a semiconductor (reduced GO – rGO – has a conductivity that is 33,000 times higher than that of doped hydrogenated amorphous silicon).

The innovation the researchers are pioneering is the use of a heated AFM tip on GO to precisely create nanoribbons of rGO. The group – from Georgia Tech, Naval Research Lab, Chung Ang University (Korea), University of Illinois at Urbana-Champaign and CNRS-Institut Néel (France) – didn’t invent thermochemical nanolithography, but the were the first to employ TCNL, via an AFM probe tip, to reduce patterned regions of GO simply by varying the temperature of the tip.

They tested their TCNL method on both GO flakes on a SiO_x/Si substrate and large-area GO films (>15 mm²) formed from epitaxial graphene grown on the carbon face of silicon carbide. They were able to print the rGO nanoribbons at a rate of about  2 µm per second, forming ribbons as narrow as 25 nm. They were able to demonstrate the formation of nanoribbons in zigzag and cross-shaped patterns.

What’s down the road for this? The researchers envision graphene nanoelectronics made by using large arrays of independent heated probe tips that would “print” nanostructures on wafer-scale areas at high speed.

Share

Credit: Bok Yeop Ahn and Jennifer A. Lewis.

As you can see above, ACerS Fellow Jennifer Lewis and her team at the University of Illinois at Urbana-Champaign have figured out how to make intriguing and beautifully simple (yet complex) origami structures by bending and folding planar lattices. The lattices are made by extruding “inks” of ceramic, metal or polymeric materials using a precise, direct-write method.

In general, beads of inks are laid down in a particular pattern and allowed to partially dry. They are then trimmed, folded and finally annealed to complete the structure.

Direct writing of lattice. Credit: Bok Yeop Ahn and Jennifer A. Lewis.

But this makes it sound much too easy. In fact, Lewis,  Bok Yeop Ahn, David Dunand and others in her team faced significant materials and technical challenges. In a University press release, Lewis says, “Most of our inks are based on aqueous formulations, so they dry quickly. They become very stiff and can crack when folded.”

She says the challenge, then, was to find a solution that would render the printed sheets pliable enough to manipulate, yet firm enough to retain their shape after folding and annealing. The answer came by combining  wet-folding origami techniques (where paper is partially wetted to enhance its foldability) with special inks containing a mixture of fast- and slow-drying solvents.

The combination yields a lattice that can can be partially dry but flexible enough to fold through multiple steps. The origami crane - requiring 15 steps – allows them to demonstrate the agile possibilities of their methods.

For Lewis, a professor of materials science and engineering and the director of the university’s Frederick Seitz Materials Research Laboratory, these structures have a serious side. “By combining these methods, you can rapidly assemble very complex structures that simply cannot be made by conventional fabrication methods,” Lewis says.

Practically speaking, this technique could provide an alternative to existing “rapid prototyping” approaches to build scaffolds for tissue engineering. There are limits to rapid prototyping, which builds 3D structures by laying down layer after layer of material, due to the sagging of lower layers or compressing under their own weight.

Lewis’ team’s method could create light, strong structures that can be bent, folded and rolled out of lattices  formed from nearly any pattern. Stents, bone-repair scaffolds, biomedical devices or even catalytic substrates are possible.

Samples of stents and other structures. Credit: Bok Yeop Ahn and Jennifer A. Lewis.

Dunand says the next step is to try larger and much smaller structures and test ink compositions that would contain other ceramic and metallic materials.

“We’ve really just begun to unleash the power of this approach,” Lewis said.

A short video providing a closer look at some of the structures is available here.

Adding . . . Advanced Materials published a paper on this work, and if you look in the comments, the editor of the magazine has kindly posted a link for a free download of the paper.

Share

(Either JavaScript is not active or you are using an old version of Adobe Flash Player. Please install the newest Flash Player.)

In the revolutionary way that aerogel is starting to redefine insulation, geopolymer may be poised to redefine cement, concrete and a lot of other advanced composite materials. And, like aerogel, geopolymer hasn’t received the public attention it should.

In this video,  geopolymer expert Trudy Kriven, a professor of material science at the University of Illinois at Urbana-Champaign, explains how geopolymers are essentially inorganic polymers made from readily available aluminum- and silica-containing materials.

As Kriven explains, a motive for finding a replacement like geopolymer for traditional Portland cement is environmental: Portland cement production requires a tremendous amount of energy to heat and convert the raw materials (at 1450°C), and can generate nearly one ton of CO₂ for every ton of processed cement.

Geopolymer, on the other hand, doesn’t have to be fired. In addition, Kriven notes, geopolymer is twice as strong as cement in compression, three-times as strong in flexure and can set up in one day.

The reality is that given the need to reduce global CO₂ emissions and given the plans for large scale construction and transportation growth in countries such as China, alternatives to Portland cement are extremely important.

Besides using geopolymer to make concrete, this novel material can be used for fire and corrosion resistant coatings, water and air filtration, CO₂ sequestration materials, projectile armor, substrates for solar and fuel cells, and even a paint substitute.

Adding for clarification . . . Trudy’s comments at around the 3 minute mark can be misconstrued when she says the geopolymer “looks like a ceramic, feels like a ceramic, but wasn’t fired at high temperature.” She is referring to “traditional” ceramics that are fired in a kiln or sintered. However, geopolymer falls within the broad grouping of “ceramic materials.”

Share