By Neal Singer
Certain fish species blend with their environment by changing color like chameleons. Their tiny motor proteins carry skin pigment crystals in their “tails” as they walk with their “feet” along the microtubule skeletons of cells to rearrange the animal’s color display.
In two recent papers, Sandia researchers have demonstrated that, in theory, they could produce a similar color change to enable synthetic or hybrid materials to change color like fish do.
“Military camouflage outfits that blend with a variety of environments without need of an outside power source — blue, say, when at sea, and then brown in a desert environment — is where this work could eventually lead,” says principal investigator George Bachand (1132). “Or the same effect could be used in fabricating chic civilian clothing that automatically changes color to fit different visual settings.”
The power source for both the biological and the lab method relies on the basic cellular fuel called ATP, which releases energy as it breaks down. Fifty percent (roughly) is absorbed by the motor proteins.
To switch motor proteins on and off, nature uses complex signaling networks. The Bachand group’s switch is simpler. It involves the genetic insertion of a new binding pocket — a kind of docking port — in the motor protein’s structure. What’s bound and released are zinc ions. Bound zinc ions turn the protein’s action to “off.” Stripping zinc ions out with chemical agents allows the motor protein to work again. The effect is controllable, and even reversible.
Introducing an on/off switch
“We essentially reengineered the protein structure to introduce an on/off switch into the motor,” says George. “So we can now turn our nanofluidic devices on and off.”
Previous efforts at regulating motor activity have used fuel intake as a control mechanism: the less the fuel, the slower the process. The Bachand group’s switch operates independently of fuel by reversibly “freezing” the motor. The advance resembles the improvement in early automobile technologies when a simple ignition switch took over for more complicated rheostats. The paper describing this work was a spotlighted article in the journal Biotechnology and Bioengineering (vol. 100, p. 478).
But what is it that the switch operates?
In a cover article in the high-profile journal Advanced Materials (Dec. 2, 2008), the Sandia team describes a kind of inverted cellular world where motor proteins do not run about but instead are upended so that their tails are embedded in a protein-modified layer on a glass slide. Microtubules — cylindrical protein filaments — instead of forming the stationary cellular skeleton of cells, are passed along by the waving feet of the motor proteins like crowd surfers at a rock concert, or like buckets passed hand-to-hand along a line of firefighters.
Protein-coated quantum dots
Coating the biotin (vitamin H)-modified microtubules are protein (streptavidin)-coated quantum dots — nanoscopic groups of atoms that emit light, their frequency dependent on dot size.
Though the dots operate differently from pigment crystals — the dots do not emit the same frequency of light that they adsorb, while the biological system merely reflects incoming wavelengths — they can perform a similar coloring function.
When the motors transport the microtubules and collisions occur, the microtubules tend to stick together and twist until they resemble the cord of a desk phone. The twisting process ultimately forces the formation of stable rings of approximately five micrometers diameter. Their docked quantum dots of cadmium selenide produce a particular range of light frequencies. When mechanical strain in the rings causes them to rupture, the cracked segments are tugged out by the nearby motors until the ring is completely disassembled. The formation and destruction of the two states — free microtubules and rings — can also be reversibly controlled.
A tug-of-war between motor groups
The process resembles the action of fish color changes, which require one group of motor proteins carrying pigments to be “on” all the time while a second group of motor proteins is turned on by complex biological processes at the right time. This produces a tug-of-war between motor groups that results in pigment dispersion and ultimately a color change. When the second motor is switched off, the color returns to the ground aggregate state.
“Our overall process mimics the fish,” says George. “We essentially go from a dispersed particle state to a concentrated one and then back again to dispersed, similar to the fish. Thus, in principle, the mechanism could produce a color change. The underlying science provides a new basis for materials scientists to begin working toward real-world applications.”
The work was supported by DOE Basic Energy Sciences and Sandia’s LDRD office.
Key contributors to the Biotechnology & Bioengineering paper were Adrienne Greene (1132) and Amanda Trent (now a graduate student at University of California, Santa Barbara). Advanced Materials paper contributors were Haiqing Liu (now at Los Alamos National Laboratory), Erik Spoerke (1816), Marlene Bachand (1132), Steve Koch (former Sandia, now an assistant professor at the University of New Mexico), and Bruce Bunker (1816). -- Neal Singer
By Mike Janes
Recognizing the need for new energy solutions in the transportation sector that balance climate, security, and sustainability, Sandia has launched a new, Labs-wide venture aimed at filling this void through large-scale public-private partnerships with an array of domestic and international research institutions and programs.
Known as the Hub for Innovation in the Transportation Energy Community (HITEC), the effort will focus on vehicle engine efficiency, vehicle electrification, and low-carbon alternative fuels, all with an underpinning of systems analysis. The new initiative is led by Transportation Energy Center 8300 Director Bob Carling and his deputy Andy McIlroy, who are identifying potential industry, national laboratory, and university partners via personal contacts and state, national, and international conferences and events.
“We’re aggressively reaching out to the private sector and other entities that can join HITEC and help bridge the gaps between research, policy, and the marketplace for transportation energy,” says Andy.
Bob says HITEC, with the Combustion Research Facility (CRF) as its core, is being developed in parallel with the National Energy Innovation Initiative (NEII), spearheaded by Terry Michalske (6100). Other members of the HITEC senior management team include Bob Hwang (1130), Justine Johannes (1811), Cara Johnson (2540), John Merson (6310), Pat Falcone (8110), Denise Koker (8520), and Art Pontau (8360). Still, even as Sandia leads the effort, Bob says HITEC won’t necessarily be “owned” or directed by Sandia. Those responsibilities, he says, will be shared with HITEC partners.
In January, members of the HITEC team, largely composed of staff members in the business development support group (8529), actively participated in a series of overseas conferences and meetings with a variety of international companies and potential HITEC partners, including BP Alternative Energy, Ricardo, and Lotus Engineering. In addition, Sandia and HITEC served as sponsors at a recent transportation energy conference organized by CALSTART (a California-based organization dedicated to supporting and accelerating the growth of the advanced transportation technologies industry and its related markets). Groups like CALSTART could help broker even more key relationships, especially with companies in the state of California.
In addition to the outreach to industry, HITEC team members Bruce Balfour, Jill Micheau, Craig Smith, and Carrie Burchard (all 8529) have been researching other public-private partnership models that successfully mirror HITEC. Bruce and Jill, for instance, visited the Science and Enterprise Park at Loughborough University in Loughborough, UK, and met with the management of the Energy Technologies Institute (ETI) and Cenex, the UK’s Centre of Excellence for Low Carbon and Fuel Cell Technologies. Their hosts, Bruce said, proved very helpful in explaining the inner workings of ETI’s organizational structures and lessons learned in running an industry-driven public-private partnership.
R&D — and D
While Sandia tends to be very adept at traditional research and development, Bob says HITEC aims to add another D — demonstration — to the familiar “R&D.”
“Much like a recent General Motors project — which entailed science-based engineering and demonstration of a hydrogen fuel system — one of HITEC’s objectives will be to produce viable, real-world transportation energy solutions that can bridge the gap between research labs and commercial products,” says Bob.
“HITEC partners will include US and international transportation companies, energy firms, research organizations, and universities, as well as other DOE laboratories,” says Bob. The first order of business, he points out, is to identify representatives from a group of flagship partners who will form the basis of a steering committee. That team, Bob says, will help select the specific areas of research on which HITEC will focus, develop a workable funding structure, and help guide other hub decisions and priorities. Though no partners have yet committed to the venture, letters of support have been signed by several entities, and follow-up meetings are planned with several potential partners.
‘Open campus’ and other synergies
In the future, facilities and space for HITEC could come into play as the Livermore Valley’s “Open Campus” begins to come to fruition. Sandia and Lawrence Livermore Lab are creating the campus, which will allow greater international scientific engagement, enable closer interaction with industry and academia, and spur local economic development by providing opportunities for start-ups and technical spin-offs.
As currently envisioned, the proposed open campus will be anchored by two facilities, an LLNL-led International Center for High Energy Density Science and the Sandia-led HITEC. In a separate venture that could create additional synergies, the city of Livermore is also considering the creation of a technology park in an area near the campus.
Though he’s optimistic about the energy and enthusiasm surrounding the HITEC launch, Bob says a number of issues still need to be resolved before it’s a viable program.
“Through what channels can we most effectively articulate the benefits of HITEC to potential partners? What role will we define for academia? We believe we’ve got an excellent value proposition to offer, and we intend to enhance it as we continue to engage our partners,” says Bob.
Bob believes the foundation for a successful HITEC venture is in place at Sandia. “The timing couldn’t be better,” he says. “There’s a clear need, a new secretary of energy, and a new administration that has stated a commitment to energy security and innovation in transportation energy. Sandia has a distinctive blend of capabilities that make us an ideal entity to lead this effort. I expect us to succeed.”
Those interested in learning more about HITEC are invited to visit its website at: www.HITECtransportation.org.
Treating brackish water for human consumption “can be done and be done affordably” here in New Mexico and other parts of the country, says Mike Hightower (6332), Sandia water researcher.
Mike was among several presenters who recently talked at a public forum in Albuquerque about the promises and perils of desalination of saline or brackish waters. The event was sponsored by the Middle Rio Grande Water Assembly, a nonprofit group that focuses on water issues, and the University of New Mexico’s Water Resources Program.
“The cost of treating ocean and brackish water has fallen enough that it can be comparable to the expenses associated with developing new freshwater supplies,” Mike says. “It used to cost 50 cents per thousand gallons of water to supply freshwater. That is now up to $3 to $4 per thousand of gallons of water — due largely to the fact that freshwater near cities is generally already being used and utilities frequently have to pump water long distances, often as far as 100 miles, to get new freshwater supplies. This raises the cost of new water supplies and the associated price of water.”
At the same time, the cost of treating saline and brackish water has come down — to $2 to $3 per thousand gallons for water being treated at the ocean and $4 to $6 per thousand gallons for inland treatment.
“By the mid ‘90s you started to see the increasing costs of freshwater intersecting with the reduced costs of treating saline and brackish water,” Mike says.
It’s unlikely, however, that future water bills will be tripling or quadrupling because water that has been desalinized through processes such as reverse osmosis will often be only used to supplement current freshwater resources, not as the sole drinking water source for communities. It will become one of many tools in the toolbox, such as efficiency improvements and wastewater reuse, to meet future water supply demands.
30 million gallons of water a day
The use of desalinized water is growing more popular in places like Alamogordo, N.M., and El Paso, Texas, two communities that sit in the Tularosa Basin, which contains an essentially underground lake with brackish water that is 2,000 to 4,000 parts per million (ppm) total dissolved solids (TDS), better known as salt. The most easily treatable form of brackish groundwater has from 2,000 to 5,000 ppm TDS, so the groundwater in the Tularosa Basin falls well within the limits.
El Paso recently constructed the world’s largest inland desalination plant to produce 25 percent of the city’s water, or about 30 million gallons of water a day. Other communities in the Tularosa Basin that could use this brackish groundwater include White Sands Missile Range, Carrizozo, Corona, Chaparral, and Horizon City. Horizon City already has a working plant, and Alamogordo has obtained water rights to start a desalination plant there. Alamogordo is also the location of the Brackish Groundwater National Desalination Research Facility that was opened last year to support research and development of new desalination and concentrate management approaches for brackish groundwater.
West Mesa potential
Recently, brackish groundwater identified under Albuquerque’s West Mesa has received a lot of attention and studies and testing are currently underway to assess the costs and sustainability of this potential new water supply. However the water is more than 10,000 ppm TDS, much higher than normally considered for cost-effective treatment, and its potential is being assessed carefully.
Mike says a 1974 report, “New Mexico Water Resources Assessment for Planning Purposes,” estimated there are 15 billion acre-feet of groundwater in New Mexico. Seventy-five percent of that is brackish.
“The problem with that estimate is that the brackish water estimates include water down to 4,000 to 5,000 feet below the surface,” he says. “Freshwater is generally less than 500 feet below the surface.”
It is easier to get the freshwater, and no one has ever really done much pumping of the brackish waters 4,000 to 5,000 feet deep.
“We may be significantly overestimating the amount of recoverable brackish water — water that is easy to get to and use,” Mike says. “Some analyses suggest that the amount we can recover is only a fraction of the initial estimate. We won’t know until more testing is done. If it’s not economically recoverable, the water will not help us much and should not be counted on.”
The question asked at the public forum where Mike made his presentation was “Is desalination a silver bullet or pipe dream?”
“It’s not a silver bullet and definitely not a pipe dream either,” Mike says. “It is a reality. In the US, desalination treatment has increased by a factor of four over the past 15 years. Desalination is used in most all 50 states and in many countries all over the world. It is accepted and can be a cost-effective approach to supplement current freshwater resources and meet our future water supply needs.” — Chris Burroughs