Graphene : Elasticity meets electronics on atom-thin membranes

The speaker at the physics colloquium this week was Prof. Manu Jaiswal from the Dept. of Physics, IITM and his talk was about graphene, exciting research on the elasticity of graphene coatings/layers and on the recent developments in the field.

The talk started off with Zidane's penalty kick of the football world cup and at the end, he pointed out how the shape of the goal net has changed. He mentioned that physicist and mechanical engineers aren't the only people working on material elasticity, so are footballers, so to speak. The goal net design changed in 2002 from being a square net to a hexagonal net. It was shown, through simulations, how stress propagates along the two structures and how hexagonal structures behave like a 2D isotropic body where as square nets have local minima along the grid outlines.

Moving on the talk, he mentioned how he himself got involved in understanding the elasticity of graphene. As is the case with many-a-stories in science, results that couldn't be explained from earlier experiments were what pushed him to ask questions about elasticity of graphene. He talked about how studying the variation of resistivity of graphene layers on SrTiO3 with temperature helped them understand that a change in the morphology of the substrate on which graphene is grown can lead to a change in the resistivity of the graphene layer above. They explored this idea further by developing micro hydrogels. To be put simply, hydrogels are those that grow in size upon absorption of water. Similarly, in their lab, they worked on developing a structure of micro hydrogels that would grow in size upon hydration. The graphene layer would be deposited pre-hydration and it would be studied post-hydration, the effects of shear stress on the conductivity and effects, if any, when the graphene layer is completely detached (delaminated) from the substrate at certain regions. Think of a tent, held up by poles on all four sides and covered by a tarp. Now think of what will happen if the poles grow in size but the size of the tarp remains the same! Now imagine a thousand poles and a large tarp, where the poles are the micro hydrogels and the tarp or the covering is the graphene layer. He talked about theoretical and experimental results as to how the resistivity of the graphene layer changes during this process. He concluded his talk by talking about graphene origami electronics where graphene sheets would be bent, twisted and strained at will to create directional conductivity, to be used as processing elements or chips. I have skipped quite a few things that he talked about but well, this is the part that I understood and that I could follow.

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