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Dirac’s Plate Trick, the Hairy Ball Theorem and more: Research probes physics of irregular objects on inclined planes

How gravity causes a perfectly spherical ball to roll down an inclined plane is part of the elementary school physics canon. But the world is messier than a textbook.

Scientists in the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have sought to quantitatively describe the much more complex rolling physics of real-world objects. Led by L. Mahadevan, the Lola England de Valpine Professor of Applied Mathematics, Physics, and Organismic and Evolutionary Biology in SEAS and FAS, they combined theory, simulations, and experiments to understand what happens when an imperfect, spherical object is placed on an inclined plane.

Published in Proceedings of the National Academy of Sciences, the research, which was inspired by nothing more than curiosity about the everyday world, could provide fundamental insights into anything that involves irregular objects that roll, from nanoscale cellular transport to robotics.

Nanowires keep surfaces sterile with silver and electricity

Metals like silver, gold and copper can kill bacteria and viruses. An electric current can also eliminate microorganisms. A team of U of A researchers combined the two approaches and created a new type of antimicrobial surface.

“It is a ,” said physicist Yong Wang, one of the lead researchers on the project. “It’s not like 1+1=2. When we combine the two, it’s much more effective.”

In , the new technology, which uses thin nanowires of silver to carry a microampere electric current, eliminated all the E. coli bacteria on glass surfaces.

DNA-loaded lipid nanoparticles are poised to bring gene therapy to common chronic diseases

A breakthrough in safely delivering therapeutic DNA to cells could transform treatment for millions suffering from common chronic diseases like heart disease, diabetes, and cancer.

A new process that transports DNA into cells using tiny fat-based carriers called lipid nanoparticles (LNPs) developed by researchers at the Perelman School of Medicine at the University of Pennsylvania improved the process of turning on the DNA’s instructions in mice to make proteins inside cells, which is crucial in fighting disease. Signs also point to an improvement in reducing treatment risks, such as immune reactions, as compared to older DNA transfer techniques.

The team’s findings were recently published in Nature Biotechnology.

Scalable nanotechnology-based lightsails developed for next-generation space exploration

Researchers at TU Delft and Brown University have developed scalable nanotechnology-based lightsails that could support future advances in space exploration and experimental physics. Their research, published in Nature Communications, introduces new materials and production methods to create the thinnest large-scale reflectors ever made.

Lightsails are ultra-thin, reflective structures that use laser-driven radiation pressure to propel spacecraft at high speeds. Unlike conventional nanotechnology, which miniaturizes devices in all dimensions, lightsails follow a different approach. They are nanoscale in thickness—about 1/1000th the thickness of a human hair—but can extend to sheets with large dimensions.

Fabricating a as envisioned for the Breakthrough Starshot Initiative would traditionally take 15 years, mainly because it is covered in billions of nanoscale holes. Using advanced techniques, the team, including first author and Ph.D. student Lucas Norder, has reduced this process to a single day.

3D nanotech blankets offer new path to clean drinking water

Researchers have developed a new material that, by harnessing the power of sunlight, can clear water of dangerous pollutants. Created through a combination of soft chemistry gels and electrospinning—a technique where electrical force is applied to liquid to craft small fibers—the team constructed thin fiber-like strips of titanium dioxide (TiO₂), a compound often utilized in solar cells, gas sensors and various self-cleaning technologies.

Despite being a great alternative energy source, solar fuel systems that utilize TiO₂ nanoparticles are often power-limited because they can only undergo photocatalysis, or create , by absorbing non-visible UV light. This can cause significant challenges to implementation, including low efficiency and the need for complex filtration systems.

Yet when researchers added copper to the material to improve this process, their new structures, called nanomats, were able to absorb enough light energy to break down harmful pollutants in air and water, said Pelagia-Iren Gouma, lead author of the study and a professor of materials science and engineering at The Ohio State University.

Single-qubit sensing puts new spin on quantum materials discovery

Working at nanoscale dimensions, billionths of a meter in size, a team of scientists led by the Department of Energy’s Oak Ridge National Laboratory revealed a new way to measure high-speed fluctuations in magnetic materials. Knowledge obtained by these new measurements, published in Nano Letters, could be used to advance technologies ranging from traditional computing to the emerging field of quantum computing.

Many materials undergo phase transitions characterized by temperature-dependent stepwise changes of important fundamental properties. Understanding materials’ behavior near a critical transition temperature is key to developing new technologies that take advantage of unique physical properties. In this study, the team used a nanoscale quantum sensor to measure spin fluctuations near a phase transition in a magnetic thin film. Thin films with magnetic properties at room temperature are essential for data storage, sensors and electronic devices because their magnetic properties can be precisely controlled and manipulated.

The team used a specialized instrument called a scanning nitrogen-vacancy center microscope at the Center for Nanophase Materials Sciences, a DOE Office of Science user facility at ORNL. A nitrogen-vacancy center is an atomic-scale defect in diamond where a nitrogen atom takes the place of a carbon atom, and a neighboring carbon atom is missing, creating a special configuration of quantum spin states. In a nitrogen-vacancy center microscope, the defect reacts to static and fluctuating magnetic fields, allowing scientists to detect signals on a single spin level to examine nanoscale structures.

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