STROBE in the News

How do you keep the world’s tiniest soda cold? UCLA scientists may have the answer.

A team led by UCLA physics professor Chris Regan has succeeded in creating thermoelectric coolers that are only 100 nanometers thick — roughly one ten-millionth of a meter — and have developed an innovative new technique for measuring their cooling performance.

“We have made the world’s smallest refrigerator,” said Regan, the lead author of a paper on the research published recently in the journal ACS Nano.

To be clear, these miniscule devices aren’t refrigerators in the everyday sense — there are no doors or crisper drawers. But at larger scales, the same technology is used to cool computers and other electronic devices, to regulate temperature in fiber-optic networks, and to reduce image “noise” in high-end telescopes and digital cameras.

The Pew Charitable Trusts has announced the 2020 grantees of the Pew Innovation Fund which supports research collaborations among alumni of their biomedical programs. This year, six pairs of researchers will partner on some of the most complex questions in human biology and disease. From neuroscience and virology to biophysics and computational biology, the 2020 Innovation Fund teams are combining their expertise to explore a variety of research areas.

Pew Scholars Polina Lishko, from the University of California, Berkeley and Buck Institute for Research on Aging and Ke Xu, from the University of California, Berkeley and a Chan-Zuckerberg Biohub Investigator, will collaborate to investigate the role of steroid hormones in Alzheimer’s, a disease affecting more than 5.8 million Americans aged 65 or older in 2020.

Ultrashort light pulses on the time scale of attoseconds provide a window into some of the fastest electronic effects occurring in solid-state systems. Obtaining structural information through coherent diffractive imaging is usually done with monochromatic x-ray sources. However, ultrashort pulses are inherently broadband, and getting transient structural information on such short time scales is challenging. Rana et al. describe a method that works with the broadband nature of ultrashort pulses. They split the pulses into 17 different wavelengths and then used an algorithm to computationally stitch together the diffraction patterns from each wavelength to reveal the structural image optimized across all wavelengths. Demonstrating the technique at optical wavelengths illustrates the feasibility of applying the method to ultrafast x-ray pulses.

Phys. Rev. Lett. 125, 086101 (2020).

A new algorithm could allow researchers to capture attosecond, multiwavelength images of an object. Illuminating a sample with attosecond x-ray pulses could let researchers image phenomena as fleeting as the rearrangement of electrons during chemical reactions. The uncertainty principle dictates that ultrashort pulses have a broad energy spectrum. However, because focusing different wavelengths typically requires multiple sets of optics, most attempts at attosecond imaging are spectroscopic, ignoring all but one radiation frequency. Now, Jianwei Miao at the University of California, Los Angeles, and colleagues have developed an innovative algorithm that can simultaneously reconstruct multiple images of an object at different wavelengths using attosecond pulses. The method offers a way to take spectroscopic images without the need for sophisticated instruments.

The coronavirus pandemic upended schools in the spring of 2020, sending students and faculty home. This rapidly changed how instructors handled laboratory physics courses. With a NSF RAPID grant, JILA Fellow Heather Lewandowski asked instructors what worked—and what didn’t—as they moved their lab courses online.

Extremely thin films of dielectrics and other materials play vital roles in many types of advanced microelectronics, but their tiny dimensions and atomic make-up can impair mechanical performance.

Now, researchers at the NSF STROBE Science and Technology Center in the U.S. have shown they can characterize the mechanical properties of silicon-carbide films as thin as 5 nm using tabletop sources of extreme ultraviolet laser light—showing them to be far softer than thicker films of the same material (Phys. Rev. Mater., doi: 10.1103/PhysRevMaterials.4.073603).

CU Boulder researchers have used ultra-fast extreme ultraviolet lasers to measure the properties of materials more than 100 times thinner than a human red blood cell. The team, led by scientists at JILA, reported its new feat of wafer-thinness this week in the journal Physical Review Materials. The group’s target, a film just 5 nanometers thick, is the thinnest material that researchers have ever been able to fully probe, said study coauthor Joshua Knobloch. “This is a record-setting study to see how small we could go and how accurate we could be,” said Knobloch, a graduate student at JILA, a partnership between CU Boulder and the National Institute of Standards and Technology (NIST). He added that when things get small, the normal rules of engineering don’t always apply. The group discovered, for example, that some materials seem to get a lot softer the thinner they become.

Many of the life’s elementary processes and material properties are determined by how molecules couple and interact. Until recently, it’s been impossible to see how these molecules interact with each other with a high enough resolution. The Raschke Group has used infrared lasers and a new microscope to get a high-resolution view of molecular coupling in porphyrin nanocrystals.

A team of scientists has developed four-dimensional (the three dimensions of space plus the fourth dimension of time) atomic electron tomography. Tomography is a technique for creating images of cross sections of an object using X-rays or ultrasound. The technique directly images the dynamics of structural changes at the atomic scale during nucleation. Nucleation is the creation of structure in a vapor, solution, or liquid. The scientists found that the nuclei came in a broad range of shapes and sizes and possess a diffuse interface surrounding a stable core. Their observations challenge the long-held classical nucleation theory that posits nucleation begins with the formation of perfectly spherical nuclei that grow after they reach a certain critical size.

Two scientists at the University of Colorado Boulder, Professor Henry Kapteyn and Professor Margaret Murnane, a married couple and partners in physics research, have been awarded the 2020 Benjamin Franklin Medal in Physics by the Franklin Institute. lt is one of several awards given out yearly by the institute. In its 196th year, the Franklin Institute continues to pay tribute to its namesake, Benjamin Franklin, by honoring the greatest minds in science. “The Franklin Institute Awards pay tribute to America’s original scientist, Benjamin Franklin, by honoring the greatest minds in science, engineering, and industry,” said Chris Franklin, chair of the Awards Corporate Committee, in a statement. “We believe in the work the Institution does to inspire a passion for learning about science and technology.” Professor Margret Murnane believes that sharing the honor with her husband is one of the best parts about winning the award.