Category Archives: News Updates

Scientists affiliated with leading research institutions across the U.S. state in a letter published Monday in the journal Science that researchers across disciplines must converge to deliver clear public health guidance about how SARS-CoV-2 is spread in the air.

The researchers write in the open letter that the scientific community must clarify the terminology used related to aerosols and droplets, and employ a more modern size threshold, rather than the existing one based on 1930s-era work. Authors include experts from the University of California San Diego, University of Maryland, Virginia Tech, and others.

Public health officials should make a clear distinction between droplets ejected by coughing or sneezing — which have inspired the social distancing mantra of six feet of separation between people — and aerosols that can carry the virus for much greater distances. Viruses in aerosols smaller than 100 microns can remain airborne in a confined space for prolonged periods of time, and accumulate in poorly ventilated air, leading to transmission.

“The balance of attention must be shifted to protecting against airborne transmission,” said the group, led by Kimberly Prather, Director of the National Science Foundation-funded Center for Aerosol Impacts on Chemistry of the Environment based at Scripps Institution of Oceanography at UC San Diego.

“Viruses in aerosols can remain suspended in air for many seconds to hours, like smoke, and be inhaled,” according to the letter. “They are highly concentrated near an infected person, so they can infect people most easily in close proximity. But aerosols containing infectious virus can also travel more than [two meters] and accumulate in poorly ventilated indoor air, leading to superspreading events.”

In addition to mask wearing, social distancing and hygiene efforts, the researchers urge for public health officials to articulate the importance of moving activities outdoors, improving indoor air using ventilation and filtration, and improving protection for high risk workers.

“The goal of this letter is to make it clear that the SARS-Cov-2 virus travels in the air and people can become infected via inhalation,” said Prather, a distinguished professor who holds a joint appointment between UC San Diego’s Scripps Institution of Oceanography and its Department of Chemistry and Biochemistry. “It is important to acknowledge this pathway so efforts can focus on cleaning the air and providing guidance on how to avoid risky indoor settings.”

Co-author Linsey Marr, the Charles P. Lunsford Professor of Civil and Environmental Engineering at Virginia Tech and an expert on airborne transmission of viruses, added, “It is important for people to wear masks at all times in public buildings and confined spaces, not only when we can’t maintain social distance. This isn’t just an academic question, but a point that will help reduce transmission if public health officials offer clear and forceful guidance about this.”

Along with Prather and Marr, letter authors include physicians Robert Schooley of UC San Diego School of Medicine, Melissa McDiarmid and Donald Milton of the University of Maryland, and Mary Wilson of the University of California, San Francisco School of Medicine and Harvard T.H. Chan School of Public Health.

Researchers at the National Institute of Standards and Technology (NIST) have developed a new method of 3D-printing gels and other soft materials. Published in a new paper, it has the potential to create complex structures with nanometer-scale precision. Because many gels are compatible with living cells, the new method could jump-start the production of soft tiny medical devices such as drug delivery systems or flexible electrodes that can be inserted into the human body.

A standard 3D printer makes solid structures by creating sheets of material — typically plastic or rubber — and building them up layer by layer, like a lasagna, until the entire object is created.

Using a 3D printer to fabricate an object made of gel is a “bit more of a delicate cooking process,” said NIST researcher Andrei Kolmakov. In the standard method, the 3D printer chamber is filled with a soup of long-chain polymers — long groups of molecules bonded together — dissolved in water. Then “spices” are added — special molecules that are sensitive to light. When light from the 3D printer activates those special molecules, they stitch together the chains of polymers so that they form a fluffy weblike structure. This scaffolding, still surrounded by liquid water, is the gel.

Typically, modern 3D gel printers have used ultraviolet or visible laser light to initiate formation of the gel scaffolding. However, Kolmakov and his colleagues have focused their attention on a different 3D-printing technique to fabricate gels, using beams of electrons or X-rays. Because these types of radiation have a higher energy, or shorter wavelength, than ultraviolet and visible light, these beams can be more tightly focused and therefore produce gels with finer structural detail. Such detail is exactly what is needed for tissue engineering and many other medical and biological applications. Electrons and X-rays offer a second advantage: They do not require a special set of molecules to initiate the formation of gels.

But at present, the sources of this tightly focused, short-wavelength radiation — scanning electron microscopes and X-ray microscopes — can only operate in a vacuum. That’s a problem because in a vacuum the liquid in each chamber evaporates instead of forming a gel.

Kolmakov and his colleagues at NIST and at the Elettra Sincrotrone Trieste in Italy, solved the issue and demonstrated 3D gel printing in liquids by placing an ultrathin barrier — a thin sheet of silicon nitride — between the vacuum and the liquid chamber. The thin sheet protects the liquid from evaporating (as it would ordinarily do in vacuum) but allows X-rays and electrons to penetrate into the liquid. The method enabled the team to use the 3D-printing approach to create gels with structures as small as 100 nanometers (nm) — about 1,000 times thinner than a human hair. By refining their method, the researchers expect to imprint structures on the gels as small as 50 nm, the size of a small virus.

Some future structures made with this approach could include flexible injectable electrodes to monitor brain activity, biosensors for virus detection, soft micro-robots, and structures that can emulate and interact with living cells and provide a medium for their growth.

“We’re bringing new tools — electron beams and X-rays operating in liquids — into 3D printing of soft materials,” said Kolmakov. He and his collaborators described their work in an article posted online on September 16, 2020, in ACS Nano.

Reference: “Electron and X-ray Focused Beam-Induced Cross-Linking in Liquids: Toward Rapid Continuous 3D Nanoprinting and Interfacing using Soft Materials” by Tanya Gupta, Evgheni Strelcov, Glenn Holland, Joshua Schumacher, Yang Yang, Mandy B. Esch, Vladimir Aksyuk, Patrick Zeller, Matteo Amati, Luca Gregoratti and Andrei Kolmakov, 16 September 2020, ACS Nano.