Lawrence Livermore researchers, in collaboration with Worchester Polytechnic Institute, have developed a new three-dimensional (3D) printing process called direct metal writing, which overcomes some of the limitations faced by 3D printing with fine metal powder fused together by lasers. Parts produced using selective laser melting and other powder-based metal techniques often have gaps or defects caused by various factors.
Instead, direct metal writing uses a metal ingot that is heated until it reaches a semi-solid state, in which solid metal particles are surrounded by liquid metal. The pastelike metal can then be forced through a nozzle. To achieve the required flow, researchers precisely control the temperature of the metal ink and how it is stirred. The process has also allowed the printing of self-supporting metal 3D structures, which had never been achieved before. The research appears in the February 27, 2017, edition of Applied Physics Letters.
“We’re in new territory,” states Wen Chen, a Livermore materials scientist and lead author of the paper. “We have developed a new, advanced metal additive manufacturing technique that people aren’t aware of yet. I think many researchers will be interested in continuing this work and expanding it into other alloys.” The technique uses a bismuth–tin mixture, which has a relatively low melting point of 300°C. Further work is needed to achieve higher printing resolution with more industry-relevant metals having higher melting points, such as aluminum and titanium. The research was supported by the Laboratory Directed Research and Development Program.
Contact: Wen Chen (925) 423-7006 (firstname.lastname@example.org).
An urgent need exists for rapid bacteria detection in rural areas and developing countries, among other applications. The current standard for bacterial identification is to isolate and grow the species in an assay, which can take hours to weeks. However, Livermore scientists, in collaboration with the University of Wisconsin at Madison, have developed a diagnostic kit that can assess up to 16 different diseases in roughly one hour. Designed to be low-cost, portable, and easy to use, the kit (shown in the image above) is about the size of a shoebox and runs on 9-volt batteries. A disposable sample container called a B-chip (bacteria-detection chip), which contains 16 microchambers, is loaded into the kit, whose B-chip reader detects pathogens by performing a recombinase polymerase amplification (RPA) assay.
Livermore principal investigator Tuan Nguyen explains, “RPA reactions are sensitive, specific, and rapid and operate at a constant, low temperature, which minimizes power consumption and simplifies heating and power handling.” The researchers tested the kit against a panel of bacterial infections called ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter), which often escape the effects of many antibiotics.
Nguyen says, “Making progress toward timely and accurate pathogen identification in an infection is the critical first step in effective patient care, especially in resource-limited environments, enabling proper usage of antibiotics to mitigate the growing emergence of antibiotic resistance.” Appearing in the February 2017 issue of Applied and Environmental Microbiology, the research was funded by the Department of Defense and the Bill and Melinda Gates Foundation, with support from the National Science Foundation.
Contact: Tuan Nguyen (925) 422-2516 (email@example.com).
A new method of generating x rays is capable of probing the size, density, pressure, and composition of highly transient states of matter, as well as studying the dynamics of high-energy-density plasmas and warm dense matter. The method was developed by a team of Livermore researchers led by physicist Félicie Albert in collaboration with the University of California (UC) at Los Angeles, SLAC National Accelerator Laboratory, Lawrence Berkeley National Laboratory, UC Berkeley, and the University of Lisbon in Portugal.
In research described in the March 31, 2017, edition of Physical Review Letters, a kilojoule-class picosecond laser was focused into a plasma to create a plasma wakefield. Each pulse from the laser overlaps with numerous plasma wake periods, and the resulting self-modulation and channeling accelerate electrons in the wake up to energies of 200 megaelectronvolts, causing the electrons to emit betatron x rays. This small-divergence broadband source of radiation can be used as a backlight to probe various samples.
To investigate betatron x-ray emission at the intensities and pulse durations relevant to larger scale laser facilities, such as the Advanced Radiographic Capability laser at the National Ignition Facility, the researchers conducted an experiment on Livermore’s Titan Laser. Betatron x-ray radiation driven by much longer, picosecond-duration laser pulses was observed. These results showed that the new radiation source holds great promise for applications at international large-scale laser facilities, where the source could be used for x-ray radiography and the phase-contrast imaging of laser-driven shocks, absorption spectroscopy, and opacity measurements.
Contact: Félicie Albert (925) 422-6641 (firstname.lastname@example.org).