How to tune thermal conductivity of 2D materials

Researchers have found an unexpected way to control the thermal conductivity of two-dimensional (2-D) materials, which will allow electronics designers to dissipate heat in electronic devices that use these materials.

2-D materials have a layered structure, with each layer having strong bonds horizontally, or “in plane,” and weak bonds between the layers, or “out of plane.” These materials have unique electronic and chemical properties, and hold promise for use in creating flexible, thin, lightweight electronic devices.

For many of these potential applications, it’s important to be able to dissipate heat efficiently. And this can be tricky. In 2-D materials, heat is conducted differently in plane than it is out of plane.

For example, in one class of 2-D materials, called TMDs, heat is conducted at 100 watts per meter per Kelvin (W/mK) in plane, but at only 2 W/mK out of plane. That gives it a “thermal anisotropy ratio” of about 50.

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Crystallized sulfur

Known to be behind the characteristic odor of rotting eggs, sulfur is essential for all living cells. Cells make proteins that form strong chemical bonds called disulfide bridges between two adjacent sulfur atoms. These bridges give strength to our hair, outer skin, and nails. Eggs are loaded with sulfur because disulfide bridges are needed to form feathers, which explains why eggs smell on rotting. Because sulfur is easy to smell, natural gas lines–which are normally odorless–have sulfur additives to help people identify and smell a gas leak when it occurs.

Image by Dr. Edward Gafford.