Anyone who has stepped into the IISc campus is aware of its enormous expanse that is comparable to the area of a small city; however, it is not quite as simple to judge the scope of scientific work done at this institute. It is the uniqueness of each laboratory that makes the work done at IISc so valuable. Some researchers here work on things as large as satellites and ships while others work with the thinnest known material, called graphene. The Nano-micro Systems Laboratory, headed by Assistant Professor Dr. Abha Misra, is busy with cutting-edge research involving materials which are classified into the lowest physical size scale.
A single layer of pristine graphite is christened graphene. It is a planar, 2D material made up of carbon atoms that are arranged in a honeycomb lattice. For around sixty years, graphene or ‘2D graphite’ was studied theoretically, and was used as a basis to understand the properties of other carbon-based materials. However, it was thought to be only an integral part of 3D structures and presumed not to exist in the free state, and was hence called an ‘academic material’. It was only in 2004 that this “theoretical toy model” turned into a brilliant reality when free-standing graphene was isolated for the first time by Andre Geim and Kostya Novoselov at the University of Manchester. The unexpected discovery was soon realised to be so important that the two of them received Nobel Prize in physics in 2010.
Dr. Misra’s laboratory studies the mechanical, thermal, electric, and photoelectric behaviour of CNTs and graphene at multiple length scales. In addition to developing a fundamental understanding of these physical systems, they have also begun working on the development of tangible technologies such as novel CNT-based nano- and micro-electrical-mechanical systems (NEMS and MEMS), chemical sensors and actuators. They have also utilized the multifunctional properties of nano-materials for various large-area sensor arrays, like flame sensors, toxic gas detection sensors, chemical-energy storage and impact absorption. “Discovering cutting-edge solutions to problems and developing them for practical application in everyday life fascinates me. I am looking into both the fundamental and the engineering aspects of low-dimensional carbon materials,” says Dr. Misra about her motivation to work in this field.
On compressing or stretching certain materials, they undergo molecular rearrangements like fluids do, but regain their original shape when the deforming force is removed. This property is called viscoelasticity, a phenomenon usually observed in polymers.The laboratory has prepared bulk CNTs and graphene structures with outstanding structural and functional properties, which remain viscoelastic over a wide range of temperatures and impact rates. Furthermore, Dr. Misra's research on the electrical-tunnelling effect in interacting CNTs can be applied in the fabrication of highly sensitive sensors.
The laboratory uses Chemical Vapour Deposition (CVD) to synthesise multi-dimensional structures of both CNT and graphene. CVD is a chemical process to fabricate high-quality solid materials. Typically, it involves the exposure of a substrate to volatile, gaseous compounds, which react or decompose on the surface of the substrate in order to produce the desired material at multiple length-scales. In general, the mechanical properties of any material measure its strength and flexibility and the electrical properties are a measure of its suitability for application as a conductor of electrons (electricity). For real practical applications it is necessary to couple both mechanical and electrical characteristics, Dr. Misra’s lab uses the technique of nano-indentation, which involves mechanical deformation of the material’s surface at nanometer length scale and analyzes its effect on current carrying capability. This phenomenon can be utilized to sense the mechanical failure and deformation limits of conducting materials by measuring ultra small change in current.
The research carried out in this laboratory is paving the way for several far-reaching real life applications of carbon nanostructures. In the future, the lab's work can influence various commercial products like precise motion controllers, highly efficient smart chemical sensors to detect toxic and explosive gases such as Methane, Carbon Monoxide and Nitrogen Monoxide in hazardous work environments, designing materials for micro-packaging used in electronic gadgets like cell phones and cameras, and photodetectors which are used in solar cells and CCD cameras.
Just as for all other ground-breaking work, interesting research is also the result of harmonious team work. Although Dr. Misra has several prestigious honours like the Young Scientist Medal from the Indian National Science Academy (INSA) to her own name, and Associate of Indian Academy of Sciences (IAS), she fondly says about her team: “I have a highly motivated research group, which includes a combination of both scientists and engineers. Each member is very hard-working and capable of bringing together novel ideas and designing the experiments, including winning awards like Gandhian Young Technological Innovation Awards, for the year 2013, and 2014.”
About the Lab: Dr Abha Misra is an Assistant Professor at the Department of Instrumentation and Applied Physics, Indian Institute of Science. She heads the Nano-micro Systems Laboratory. Email: firstname.lastname@example.org, Phone: 080-2293-3198, 3149, 2985.