Dr. Bishakh Bhattacharya, Professor, Dept. of Mechanical Engineering, IIT Kanpur

Lattice based meta-structures have shown tremendous application in electro-magnetic and sonic wave absorption which could in principle create ‘invisibility’ of an object either in optical or in acoustic domain. Existing lattice and crystal based phononic materials have however, practical limitations in terms of customizability and hence, they can be generally used in a narrow band of frequency. In this research, we have demonstrated how with the use of a micro-structured hour-glass shaped metastructure in the lattice unit, one can get a wider variation of propagation and stop bands. The hour-glasses are developed in the Smart Materials Laboratory of IIT Kanpur using additive manufacturing.

Inspiration of this lattice has come from a two-headed drum called ‘Dambaru’ or ‘Damaru’ which is used in ancient Hinduism and Tibetan Buddhism. It is said that Lod Shiva has produced a special sound through this musical instrument to create and regulate the universe.

Interestingly, in this application, we have shown the nature of stiffness of a vibrating medium could be altered drastically by controlling the lattice micro-structure from regular honeycomb to auxtetic honeycomb structure.This has wide applications in the field of vibration isolation in high speed trains,stealth submarines and helicopter rotors. We have also shown that for dynamic systems,we can control the propagation and band-gaps very effectively which can usher in the development of new ultrasonic devices with capacity of sub-wave length imaging empowering the medical practitioners and the health management industry.This work is sponsored by a SPARC project of MHRD and is the outcome of a successful collaboration between Professor Bishakh Bhattacharya and his PhD student Mr.Vivek Gupta of the Department of Mechanical Engineering,IIT Kanpur, and Professor Sondipon Adhikari of Swansea University. The work is published in the scientific report on 1^st December, 2020 with the title “Exploring the dynamics of hourglass shaped lattice Metastructures”.