Lifeboat Foundation

Researchers at Leipzig University have succeeded in moving tiny amounts of liquid at will by remotely heating water over a metal film with a laser. The currents generated in this way can be used to manipulate and even capture tiny objects. This will unlock groundbreaking new solutions for nanotechnology, the manipulation of liquids in systems in tiny spaces, or in the field of diagnostics, by making it possible to detect the smallest concentrations of substances with new types of sensor systems.

The findings are described in an article recently published in Nature Communications (“Hydrodynamic manipulation of nano-objects by optically induced thermo-osmotic flows”).

Illustration of a gold nanoparticle trapped near a locally heated gold surface by hydrodynamic and van der Waals forces. (Image: Martin Fränzl, Universität Leipzig)

Delivering what has been so challenging to produce, researchers present an engineered analog of tooth enamel – an ideal model for designing biomimetic materials – designed to closely mimic the composition and structure of biological teeth’s hard mineralized outer layer. It demonstrates exceptional mechanical properties, they say.

Natural tooth enamel – the thin outer layer of our teeth – is the hardest biological material in the human body. It is renowned for its high stiffness, hardness, viscoelasticity, strength, and toughness and exhibits exceptional damage resistance, despite being only several millimeters thick.

Tooth enamel’s unusual combination of properties is a product of its hierarchical architecture – a complex structure made up of mostly hydroxyapatite nanowires interconnected by an amorphous intergranular phase (AIP) consisting of magnesium-substituted amorphous calcium phosphate. However, accurately replicating this type of hierarchical organization in a scalable abiotic composite has remained a challenge.

The Institute for Soldier Nanotechnologies (ISN), made up of the MIT, Caltech, ETH Zurich and the US Army Research Lab, has used 3D printing technology at the nanoscale to form a material that is reportedly more effective at stopping a projectile than Kevlar or steel.

Thinner than a single human hair, the material is made from tiny carbon struts that form interconnected tetrakaidecahedrons – structures with 14 faces – that are fabricated via two-photon lithography.

According to the team, the nano-architected material could potentially replace kevlar for a wide array of bulletproof protective gear used by the armed forces.

Quantum magnets can be studied using high-resolution spectroscopic studies to access magnetodynamic quantities including energy barriers, magnetic interactions, and lifetime of excited states. In a new report now published in Science Advances, Sascha Brinker and a team of scientists in advanced simulation and microstructure physics in Germany studied a previously unexplored flavor of low-energy spin excitation for quantum spins coupled to an electron bath. The team combined time-dependent and many-body perturbation theories and magnetic field-dependent tunneling spectra to identify magnetic states of the nanostructures and rationalized the results relative to ferromagnetic and antiferromagnetic interactions. The atomically crafted nanomagnets are appealing to explore electrically pumped spin systems.

Anomalous magnetodynamics

Magnetodynamics at the atomic scale form the cornerstone of spin-based nanoscale devices with applications in future information technologies. Interactions of local spin states also play a crucial role with the local environment to determine their properties. Researchers have described the impact of orbital hybridization effects, charge transfer, and the presence of nearby impurities as strong influencers on the magnetic ground state, to determine a range of magnetodynamic qualities, including magnetic anisotropy, spin lifetime and spin-relaxation mechanisms. Experimental methods can be developed to directly capture these properties and analyze the magnetic phenomena of classical and semiclassical descriptions at sub-nanometer scales to reveal the emergence of exquisite quantum mechanical effects.

A hundred years of physics tells us that collective atomic vibrations, called phonons, can behave like particles or waves. When they hit an interface between two materials, they can bounce off like a tennis ball. If the materials are thin and repeating, as in a superlattice, the phonons can jump between successive materials.

Now there is definitive, experimental proof that at the nanoscale, the notion of multiple thin materials with distinct vibrations no longer holds. If the materials are thin, their atoms arrange identically, so that their vibrations are similar and present everywhere. Such structural and vibrational coherency opens new avenues in materials design, which will lead to more energy efficient, low-power devices, novel material solutions to recycle and convert waste heat to electricity, and new ways to manipulate light with heat for advanced computing to power 6G wireless communication.

The discovery emerged from a long-term collaboration of scientists and engineers at seven universities and two U.S. Department of Energy national laboratories. Their paper, “Emergent Interface Vibrational Structure of Oxide Superlattices,” was published January 26 in Nature.

Water flows more easily through narrower carbon nanotubes than larger ones and we have struggled to explain why. Now, one team has an answer: it may all be due to quantum friction.

Friction in its standard, classical sense is well understood by most people. The greater the degree of contact between two things moving past one another, the greater the energy needed to overcome friction. A narrow pipe has a larger wall relative to its cross-sectional area than a wider pipe, so you would expect the frictional forces experienced by water inside the smaller pipe to be proportionally greater. This means the water should flow less easily.

But carbon nanotubes don’t obey this rule. These are made of thin layers of graphite rolled into tubes just a few nanometres wide – and the narrower the diameter, the easier it is for water to flow through them.

For 15 years, scientists have been baffled by the mysterious way water flows through the tiny passages of carbon nanotubes—pipes with walls that can be just one atom thick. The streams have confounded all theories of fluid dynamics; paradoxically, fluid passes more easily through narrower nanotubes, and in all nanotubes it moves with almost no friction. What friction there is has also defied explanation.

In an unprecedented mashup of fluid dynamics and quantum mechanics, researchers report in a new theoretical study published February 2 in Nature that they finally have an answer: ‘quantum friction.’

The proposed explanation is the first indication of quantum effects at the boundary of a solid and a liquid, says study lead author Nikita Kavokine, a research fellow at the Flatiron Institute’s Center for Computational Quantum Physics (CCQ) in New York City.

An exceptionally large grant will allow a team of Empa researchers to work on an ambitious project over the next ten years: The Werner Siemens Foundation (WSS) is supporting Empa’s CarboQuant project with 15 million Swiss francs. The project aims to lay the foundations for novel quantum technologies that may even operate at room temperature – in contrast to current technologies, most of which require cooling to near absolute zero.

“With this project we are taking a big step into the unknown,” says Oliver Gröning who coordinates the project. “Thanks to the partnership with the Werner Siemens Foundation, we can now move much further away from the safe shore of existing knowledge than would be possible in our ‘normal’ day-to-day research. We feel a little like Christopher Columbus and are now looking beyond the horizon for something completely new.”

The expedition into the unknown now being undertaken by Empa researchers Pascal Ruffieux, Oliver Gröning and Gabriela Borin-Barin under the lead of Roman Fasel was preceded by twelve years of intensive research activity. The researchers from Empa’s [email protected] laboratory, headed by Fasel, regularly published their work in renowned journals such as Nature, Science and Angewandte Chemie.

A newly created nano-architected material exhibits a property that previously was just theoretically possible: it can refract light backward, regardless of the angle at which the light strikes the material.