The Laboratory in the News

Exploring Ion Transport in Nanoporous Materials

Understanding and controlling the movement of ions in porous materials and at hydrophobic interfaces is critical to a wide variety of energy and environmental technologies. However, a detailed understanding of how such transport occurs at the nanoscale is still in its infancy. In a recent study, Lawrence Livermore scientists, in collaboration with the University of California at Irvine, demonstrated that ion transport of aqueous solutions at a hydrophobic interface can be highly dependent on the size and hydration strength of the solvated ions. The team’s results appeared in the March 17, 2020, issue of ACS Nano.

As part of the research effort, the team designed nanopores containing a hydrophobic entrance on one side and a hydrophilic, highly charged entrance on the other side. During experiments, this configuration allowed the researchers to induce the wetting of nanopores using lower voltages (less than 2 volts) and explore gating—ion activation and deactivation—with different ion types. The team’s experimental results, coupled with first-principle calculations and molecular dynamics simulations, revealed that large anions, such as bromine and iodine, are prone to migrate from an aqueous solution to a hydrophobic interface. This process leads to the anion accumulation responsible for pore wetting and enhanced ion currents.

Lawrence Livermore’s Anh Pham, co-author of the research paper, explains, “The findings are important for designing nanoporous systems that are selective to ions of the same charge, as well as for realization of ion-induced wetting in hydrophobic pores.” Such systems are relevant in applications ranging from ion-selective membranes, drug delivery platforms, and biosensing to ion batteries and supercapacitors.
Contact: Anh Pham (925) 423-6501 (pham16@llnl.gov).

Harvesting Waste Heat from Untapped Sources

In the United States, thirteen quadrillion British Thermal Units (BTUs) of energy—enough to meet the nation’s total energy needs for 47 days—are lost annually to waste heat. Recently, a team of materials scientists, led by Livermore’s Alex Baker, have developed a cold-spray deposition technique to fabricate cost-efficient thermoelectric generators that can harvest waste heat from previously inaccessible sources. The research appeared in the April 8, 2020, edition of JOM (Journal of The Minerals, Metals, & Materials Society).

In conventional cold-spray deposition, micrometer-scale metal particles are entrained in supersonic gas and directed onto a metal surface. Upon impact, the particles plastically deform and bond with the surface or one another. Typically, this process has been limited to malleable materials, as functional materials, such as thermoelectrics, tend to become brittle. Funded by the Department of Energy’s Technology Commercialization Fund Program, Livermore and industrial partner TTEC Thermoelectric Technologies, LLC, used their additive manufacturing technique to cold spray thermoelectric bismuth-telluride powder onto substrates including stainless steel, aluminum silicate, and quartz. After deposition, the material showed no significant compositional change, indicating that thermoelectric generators can be fabricated without loss of integrity.

This process can be used to apply thermoelectric materials in place, creating generators that efficiently harvest waste heat emitted from components with complex shapes, such as pipes and valves. Says Baker, “We demonstrated the power and versatility of cold-spray additive manufacturing to build thermoelectric generators in locations that had been inaccessible with traditional approaches using rigid thermoelectric devices.”
Contact: Alex Baker (925) 424-3610 (baker97@llnl.gov).

Livermore Supercomputer Supports COVID-19 Research

As COVID-19 began impacting millions of people worldwide, Lawrence Livermore, Penguin Computing, and Advanced Micro Devices, Inc. (AMD), reached an agreement to upgrade the Laboratory’s Corona computing cluster with an in-kind contribution of cutting-edge AMD Instinct™ accelerators. “These accelerators boost the capability of the teams working on COVID-19,” says Livermore’s Jim Brase, the Computing Directorate’s deputy associate director for programs. “We can work faster, with more throughput.”

Using Corona, a Livermore team implemented a first-of-its-kind virtual screening platform to evaluate therapeutic antibody designs that could improve binding interactions with the antigen protein in SARS-CoV-2 (the virus that causes COVID-19). The team has narrowed the list of antibody candidates from a nearly infinite set to about 20 possibilities and has begun exploring additional antibody designs. The new accelerators allow researchers to increase the number of computationally expensive simulations they can perform, making the discovery of an effective antibody design more likely.

With the system upgrade complete as of April 2020, the Penguin Computing–built Corona machine—named for the total solar eclipse of 2017—exceeds a peak performance of 4.5 petaflops (10¹⁵ floating-point operations per second). In addition to the work being conducted by Lawrence Livermore researchers on discovery of potential antibodies and antiviral compounds, Corona is being utilized by the COVID-19 HPC Consortium, a nationwide public–private partnership involving more than a dozen member institutions in government, industry, and academia that aims to accelerate development of detection methods and treatments for the virus.
Contact: Jeremy Thomas (925) 422-5539 (thomas244@llnl.gov).