Late last year, Caltech researchers revealed that they had developed a new fabrication technique for printing microsized metal parts containing features about as thick as three or four sheets of paper. Now, the team has reinvented the technique to allow for printing objects a thousand times smaller: 150 nanometers, which is comparable to the size of a flu virus. In doing so, the team also discovered that the atomic arrangements within these objects are disordered, which would, at large scale, make these materials unusable because they would be considered weak and "low quality." In the case of nanosized metal objects, however, this atomic-level mess has the opposite effect: these parts can be three-to-five-times stronger than similarly sized structures with more orderly atomic arrangements.
The work was conducted in the lab of Julia R. Greer, the Ruben F. and Donna Mettler Professor of Materials Science, Mechanics and Medical Engineering; and Fletcher Jones Foundation Director of the Kavli Nanoscience Institute. It is described in a paper appearing in the journal Nano Letters. [Caltech story]
Andrei Faraon (BS '04), the William L. Valentine Professor of Applied Physics and Electrical Engineering, has been named a 2023 Experimental Physics Investigator by the Gordon and Betty Moore Foundation. The awards, given to 21 researchers this year, including Faraon, come with a five-year $1.25 million research grant intended to advance the field of experimental physics. [Caltech story]
For around 20 years, Caltech Professor of Applied Physics, Paul Bellan, and his group have been creating magnetically accelerated jets of plasma, an electrically conducting gas composed of ions and electrons, in a vacuum chamber big enough to hold a person. (Neon signs and lightning are everyday examples of plasma).
In that vacuum chamber, wisps of gas are ionized by several thousand volts. One hundred-thousand amps then flow through the plasma, producing strong magnetic fields that mold the plasma into a jet traveling around 10 miles per second. High-speed recordings show that the jet transitions through several distinct stages in a few tens of microseconds.
Bellan says the plasma jet looks like an umbrella growing in length. Once the length reaches one or two feet, the jet undergoes an instability that causes it to transform into a rapidly expanding corkscrew. This rapid expansion triggers a different, faster instability that creates ripples. [Caltech story]
Julia Greer, Ruben F. and Donna Mettler Professor of Materials Science, Mechanics and Medical Engineering; Fletcher Jones Foundation Director of the Kavli Nanoscience Institute, has been selected as the 2024 recipient of the Society of Engineering Science’s (SES) A.C. Eringen Medal. Greer was selected for her sustained outstanding contributions in the field of three-dimensional nano- and micro-architected materials as well as the development of innovative in-situ experimental methods and instruments used to study the mechanics of small-scale materials.
The SES A.C. Eringen Medal is awarded annually in recognition of sustained outstanding achievements in engineering science, and the award recipient is invited to speak at the SES annual meeting. The 2024 SES annual meeting will be hosted by Westlake University in China.
Lasers have become relatively commonplace in everyday life, but they have many uses outside of providing light shows at raves and scanning barcodes on groceries. Lasers are also of great importance in telecommunications and computing as well as biology, chemistry, and physics research.
In those latter applications, lasers that can emit extremely short pulses—those on the order of one-trillionth of a second (one picosecond) or shorter—are especially useful. Using lasers operating on such small timescales, researchers can study physical and chemical phenomena that occur extremely quickly—for example, the making or breaking of molecular bonds in a chemical reaction or the movement of electrons within materials. These ultrashort pulses are also extensively used for imaging applications because they can have extremely large peak intensities but low average power, so they avoid heating or even burning up samples such as biological tissues.
In a paper appearing in the journal Science, Caltech's Alireza Marandi, an assistant professor of electrical engineering and applied physics, describes a new method developed by his lab for making this kind of laser, known as a mode-locked laser, on a photonic chip. The lasers are made using nanoscale components (a nanometer is one-billionth of a meter), allowing them to be integrated into light-based circuits similar to the electricity-based integrated circuits found in modern electronics. [Caltech story]
On a cool, clear evening in May 2023, Caltech electrical engineer Ali Hajimiri and four members of his lab gathered on the roof of the Gordon and Betty Moore Laboratory of Engineering to await a signal from the heavens.
In preparation, the researchers had strewn portable floodlights across the floor and erected a collapsible canopy in a corner of the roof to shelter instruments and monitors stacked atop a small folding table. Two antennae perched nearby on heavy-duty tripods, their electronic gazes steadily tracking an invisible target drifting more than 300 miles overhead. The signal—if it came—would arrive in the form of a weak microwave beam transmitted from the Space Solar Power Demonstrator (SSPD-1), a 110-pound set of Caltech payloads that had launched into space five months earlier aboard a SpaceX rocket on the Momentus Vigoride-5 spacecraft. SSPD-1 is the first spaceborne prototype from Caltech’s Space Solar Power Project (SSPP). [Caltech story]