Graphene is a thin, flexible and strong material that is useful in electronics. It is a good conductor of heat and electricity, and helps in miniaturisation of devices that is otherwise challenging.

As electronic components continue to shrink, the challenge of managing excess heat becomes increasingly crucial for maintaining the device's performance while ensuring its longevity.

To address this, scientists at the Indian Institute of Technology, Madras (IIT-M) have proposed to control heat flow in graphene using a mechanical strain, that is using stress to control the direction of heat flow.

Thermal rectification (TR) is a ratio that highlights a material's ability to conduct heat preferentially in one direction. This ratio is a key area of focus for achieving active heat control. Reaching controlled thermal rectification in graphene has historically meant making structural modifications that are difficult and costly to create.

Sarith Sathian, Professor at the Department of Applied Mechanics and Biomedical Engineering at the Institute, co-authored the paper that appeared in the Applied Physics Journal with research scholar Dheeraj Venkata Sai Kavuri. Prof Sathian says: "A metal piece will conduct heat in both directions. At a bigger scale, direction-dependent heat transfer does not exist."

But in 2D material, like graphene, directionality has been observed. "It will conduct efficiently in one direction, but in the opposite direction, it could work as an insulator."

The team also took into account the vibrations of the material's lattice. "Phonon is a particle that carries energy. We aimed to manipulate the vibrations of the lattice in the transport of heat in material like graphene; that is, change it structurally by bending it or stretching it or compressing it. The objective is to efficiently design direction-dependent heat transfer material."

Simpler approach

The research work shows how controlled application of strain across the graphene surface helps manage heat. Their study reported that with compressive strain, heat was found to flow from highly compressed regions to less compressed ones, achieving a TR ratio of up to 120 per cent. (The higher the ratio, the better). Even in larger systems of up to 100 nm, a significant 30 per cent TR was observed. (One nanometre is one-billionth of a metre.)

By merely changing the location of the strain, it was possible to tune both the ratio as well as the direction of heat flow.

Commercial viability

The authors say that their proposed methods are "experimentally feasible as they do not involve significant geometric alterations or the production of complex structures". This could significantly reduce challenges in manufacturing and costs associated with heat control in nanoscale devices.

When eventually adopted by industry, this could lead to more efficient heat management in high-performance computing and miniaturised electronics, and other critical technological sectors such as defence. Better heat management could result in further miniaturisation of devices - which means we can pack in more within a given surface area.

Computer simulation

The team was able to validate the outcome using computer simulation models. Prof Sathian says, "Most such studies are based on limited number of lab experiments because doing experiments is expensive."

'When we do these simulations, we model the entire structure of atoms as in a real lattice graphene sheet and then apply all these conditions - such as supplying heat. Which means, we generally give more energy to the atoms at one end, but remove energy for those at the other end. We call it molecular dynamic simulations using computers."

"If we wish to vibrate an atom, we need to give an excitation to the atom. When you give some energy to the atom, the velocity keeps changing. We observe the velocity of the atom and from that velocity information we can directly calculate what the kinetic or the potential change of the atom is, and that is quantified as the energy.

We can also create a system - like take up a series of atoms and try to connect these atoms to something called the force field. As you know, any atom will attract or repel the nearby atom. What is the force of attraction between two carbon atoms in a graphene sheet? That is already well known. That means we can actually represent that mechanism in a mathematical way.

We ask the computer to simulate this mechanism and cross the outcome."

Now, what is the next step for the team?

Says Prof Sathian, "We have only done very simple geometry. The actual geometry will be different. The system in the real-world will have different layers - we have studied only one layer of wrapping. In an actual scenario there could be many layers. Calculations that take into account multiple layers would require more complex geometry."

Finally, he says he would like to collaborate with an experimental group working on such functional electronic material to develop usable devices or a technique. "That is the final frontier."

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Published on September 8, 2025

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