Highlights - 2016

Livermore engineers have achieved unprecedented scalability in 3D-printed architectures of arbitrary geometry, opening the door to super-strong, ultra-lightweight, and flexible metallic materials for aerospace, the military, and the automotive industry. In a study published online July 18 in Nature Materials, Laboratory engineers report building multiple layers of fractal-like lattices with features ranging from the nanometer to centimeter scale, resulting in a nickel-plated metamaterial with a high elasticity not found in any previously built metal foams or lattices. Metamaterials are synthetic composites with engineered properties that generally do not exist in natural materials.

Prior to this achievement, no one had been able to scale up 3D features from the nanoscale to see how they behave. The lattices were initially printed out of polymers, using a one-of-a-kind Large Area Projection Micro-Stereolithography printer invented by Livermore engineer Bryan Moran, who won an R&D; 100 award for the design. The lattice structure was then coated with a nickel-phosphorus alloy and then processed to remove the polymer core, leaving extremely lightweight, hollow tube structures of the alloy. 3D additively manufactured materials have direct application in the Laboratory’s stockpile stewardship mission, as well as in a broad array of applications requiring materials whose properties, such as compression, tension, and shear, can be tuned. The Laboratory Directed Research and Development program funded this research (15-LW-083), together with the Defense Advanced Research Projects Agency (DARPA) and a Virginia Tech startup.

Scientists have found that changes in cloud patterns during the last three decades match those predicted by climate model simulations. These cloud changes are likely to have had a warming effect on the planet. The research from Livermore, Scripps Institution of Oceanography, University of California, Riverside, and Colorado State University appears in the journal Nature.

Records of cloudiness from satellites originally designed to monitor weather are typically plagued by erroneous variability related to changes in satellite orbit, instrument calibration, and other factors. In order to combat these inconsistencies, the team used a new technique to remove the variability from the records. The corrected satellite records exhibited large-scale patterns of cloud change between the 1980s and 2000s that are consistent with climate model predictions, including retreat of mid-latitude storm tracks towards the poles, expansion of subtropical dry zones, and increasing height of the highest cloud tops. “After the spurious trends were removed, we saw consistent responses among several independent datasets and with model simulations,” says Mark Zelinka, a Livermore scientist and co-author of the paper. “That is a nice confirmation of the models’ predictions, at least for the types of cloud changes that models agree on.” The National Oceanic and Atmospheric Administration, the Department of Energy Office of Science, and NASA funded the research.

Researchers from Lawrence Livermore, the University of Melbourne, and the U.S. Geological Survey, have found a way to reveal potential microbially mediated mercury methylation (the formation of toxic methylmercury through anaerobic bacterial processes) in polar marine environments. To explore mercury methylation sources, they combined measurements of total and methylated mercury with metagenomic analysis (genomic analysis from environmental samples) of whole-community microbial DNA from Antarctic snow, brine, sea ice, and seawater. Their research paper appears in the journal Nature Microbiology. 

Atmospheric deposition of mercury onto sea ice and seawater in the polar regions provides mercury for microbial methylation and contributes to the bioaccumulation of the neurotoxin methylmercury in the marine food web. Scientists are concerned that methylmercury stored in the fatty tissues of fish will accumulate enough mercury to pose a health hazard to humans. Little is known about the controls on microbial mercury methylation in polar marine systems, but mercury methylation is known to occur alongside photochemical and microbial mercury reduction. The scientists’ research identified the marine bacterium Nitrospina as a potential mercury methylator within sea ice.

The Department of Energy’s Office of Science funded this work.

A team of Livermore researchers has developed protective yet breathable membrane materials featuring small-diameter (less than 5 nanometers) carbon nanotubes (CNT) as moisture-conductive pores. The membranes provide water vapor transport at a rate 20 times faster than those predicted by conventional gas diffusion theories, surpassing commercial breathable fabrics such as Gore-Tex. Their findings are described in a paper featured on the back cover of the July printed issue of the journal Advanced Materials.

The team reported that these new CNT membranes can efficiently block biological threats such as Dengue virus because their size prevents them from passing through. Future work will aim to encode the membrane with a smart and dynamic response to chemical hazards, which could lead to a new paradigm of adaptive, breathable, and protective materials. The work was supported by the Defense Threat Reduction Agency’s “Dynamic Multifunctional Materials for a Second Skin” program and the Laboratory Directed Research and Development program.

Livermore researchers and their colleagues have used a new experimental technique to measure the total hydrodynamic instability growth near peak velocity (about 900,000 mph or 1,400,00 km/h) of a National Ignition Facility (NIF) implosion. Their research was published online in the journal Physical Review Letters. A NIF implosion has two distinct phases—an acceleration phase and a deceleration (rebound shock) phase, both of which are unstable. For the experiment, scientists used special target capsules with pre-imposed sinusoidal modulations, or “ripples,” on the capsule surface. They measured the growth of hydrodynamic instabilities as a function of the frequency, or “mode” of the ripples (the number of ripples inscribed on the capsule).

To view the state of the implosion at peak velocity, the researchers employed a novel technique designed by Livermore physicist Bruce Hammel. They added a small amount of argon to the gas in the plastic capsule to enhance the x-ray emissions from the central hot plasma created during the shock rebound phase, effectively resulting in self-radiography. This technique allowed the scientists to achieve the highest direct measurement of hydrodynamic growth in any inertial confinement fusion experiment to date—an areal density (mass per unit area) amplification of 7,000x. The purpose of the work is to help NIF researchers to better understand hydrodynamic instabilities that inhibit nuclear fusion ignition, and develop strategies to remove this obstacle to fusion.

Livermore researchers and partners have developed the first-ever biological identification method that exploits the information encoded in proteins of human hair. Scientists from Lawrence Livermore and a Utah startup company, Protein-Based Identification Technologies, LLC, have developed the groundbreaking technique. Their work, currently funded by the Department of Defense and the Laboratory Directed Research & Development program, is described in a paper in the online journal PLOS ONE.

The method will offer another tool to law enforcement authorities for crime scene investigations as well as to archaeologists, since the technique can detect protein in human hair more than 250 years old. In their study, the researchers examined male and female hair samples of 66 European-Americans, 5 African Americans, 5 Kenyans, and 6 skeletal remains from the 1750s and 1850s, finding a total of 185 protein markers. The protein markers used by the scientists are variants resulting from amino acid substitutions that stem from DNA mutations, also known as single amino acid polymorphisms. Each person’s number of hair protein markers combined with their pattern of protein markers is unique, so researchers are able to provide a distinct pattern for an individual that would distinguish that person among a population of one million. The researchers’ ultimate goal is to establish a set of 90–100 protein markers that would identify an individual among the world’s population using a single hair—providing law enforcement with the capability of identifying remains that no current technique allows.