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Experiments reveal the factors that determine the friction between the single-atom-thick layers in van der Waals materials, which may have uses in lubrication technology.

Van der Waals (vdW) materials consist of stacked, single-atom-thick layers, and these layers can experience very low friction as they slide over one another, a property that might be exploited for lubrication. A research team has now distinguished several contributions to this low friction and has shown that effects at the edges of the sliding regions dominate [1]. Some of their experiments involved sliding a several-layer-thick flake across a surface made of a similar material containing a crack, which allowed the team to systematically control the edge length. The findings could guide efforts to engineer controllable frictional forces into such materials in micromechanical devices.

The very low friction, called superlubricity, exhibited by vdW materials has been previously shown to depend on the relative orientations of the layers. If one layer is rotated by some angle, called the twist angle, with respect to the layer below, the two layers form a “superlattice” in which the two atomic lattices fall periodically in and out of registry, like a pair of overlaid combs with slightly different spacings. This arrangement is called a Moiré pattern, and the repeating elements, or unit cells, of the superlattice are called Moiré tiles. Superlubricity arises because, in general, the contributions to the frictional force from the atoms within one Moiré tile cancel each other out: Some exert a push, while others exert a pull.

Using a 3D printer that works with molten glass, researchers forged LEGO-like glass bricks with a strength comparable to concrete. The bricks could have a role in circular construction in which materials are used over and over again.

“Glass as a structural material kind of breaks people’s brains a little bit,” says Michael Stern, a former MIT graduate student and researcher in both MIT’s Media Lab and Lincoln Laboratory. “We’re showing this is an opportunity to push the limits of what’s been done in architecture.”

Continue reading “‘Brain-breaking’ glass bricks are 3D printed, reusable, and strong” »

Researchers have created a disk-like nanostructure that dramatically improves light frequency conversion efficiency. This innovation in photonics combines material and optical resonances in a compact form, paving the way for advanced optical and photonic applications.

Scientists at Chalmers University of Technology, in Sweden, have for the first time succeeded in combining two major research fields in photonics by creating a nanoobject with unique optical qualities. Since the object is a thousand times thinner than a human hair, yet very powerful, the breakthrough has great potential in the development of efficient and compact nonlinear optical devices. “My feeling is that this discovery has a great potential,” says Professor Timur Shegai, who led the study at Chalmers.

Harnessing Light With Advanced Photonics.

Researchers have developed a new organic thermoelectric device that can harvest energy from ambient temperature. While thermoelectric devices have several uses today, hurdles still exist to their full utilization. By combining the unique abilities of organic materials, the team succeeded in developing a framework for thermoelectric power generation at room temperature without any temperature gradient.

Their findings were published in the journal Nature Communications.

Thermoelectric devices, or thermoelectric generators, are a series of energy-generating materials that can convert heat into electricity so long as there is a temperature gradient —where one side of the device is hot and the other side is cool. Such devices have been a significant focus of research and development for their potential utility in harvesting waste heat from other energy-generating methods.

2 likes, — infinitywithoutend on July 21, 2024: ‘Graphene’

Molecular materials for computing progress intensively but the performance and reliability still lag behind. Here the authors assess the current state of computing with molecular-based materials and describe two issues as the basis of a new computing technology: continued exploration of molecular electronic properties and process development for on-chip integration.

Stanford researchers mimic brain structure with ferroelectric material.

After thousands of years as a highly valuable commodity, silk continues to surprise. Now it may help usher in a whole new direction for microelectronics and computing.

Photonic crystals are materials with repeating internal structures that interact with light in unique ways. We can find natural examples in opals and the vibrant colored shells of some insects. Even though these crystals are made of transparent materials, they exhibit a “photonic bandgap” that blocks light at certain wavelengths and directions.