Vikram Deshpande - Publications#
10 significant publications in the last 5 years
1. A.B.C. Buskermolen, H. Suresh, S.S. Shishvan, A. Vigliotti, A. DeSimone, N.A. Kurniawan, C.V.C. Bouten and V.S. Deshpande (2019), Entropic forces drive cellular contact guidance, Biophysical Journal, 116, 1994-2008.
Most tissues in the human body exhibit a specific spatial organization of cells. This cellular organization plays a crucial role in the micro-architecture of tissues and dictates their biological and mechanical functioning. Deshpande in this study showed via a combination of experiments and new theoretical developments that similar to nematic ordering in liquid crystals, orientational ordering of cells on micropatterns is driven, rather counter-intuitively, by the tendency of cells to maximise morphological disorder. This finding reveals an alternative, entropy-mediated mechanism for explaining the response of cells to anisotropic environmental cues besides the often-invoked mechanisms that are predicated on very specific biochemical feedback pathways.
2. B. Liu, K. Kandan, H.N.G. Wadley and V.S. Deshpande (2019), Deep penetration of ultra-high molecular weight polyethylene composites by a sharp-tipped punch, Journal of the Mechanics and Physics of Solids, 123, 80-102.
Ultra-high molecular weight polyethylene composites now find extensive application in many protection applications including doors of civilian aircrafts. The mechanisms of their superior performance had remained mysterious. Deshpande working with his students performed elegant experiments coupled with details models including numerous microstructural features to elucidate the mechanisms of the penetration resistance of these composites. These models are now used my industries and disseminated by the manufacture of these composites.
3. S. Shishvan, G. Csányi and V.S. Deshpande (2020), Hydrogen induced fast-fracture, Journal of the Mechanics and Physics of Solids, 134, 103740.
Here Deshpande proposed, supported by detailed atomistic and continuum calculations, that unlike macroscopic toughness, hydrogen-mediated tensile failure is a result of a fast -fracture mechanism. Specifically, he showed that failure originates from the fast propagation of cleavage cracks that initiate from cavities that form around inclusions such as carbide particles. The novelty is his combined use of atomistic and solid mechanics models, with a deep understanding of diffusion theory, gives a new picture of why hydrogen leads to cracking of steels that would otherwise be tough and of high ductility. Deshpande in this publication has provided a new understanding for an old but unsolved problem with the potential to changing the way we think of developing steels that resist embrittlement.
4. S.S. Shishvan, N.A. Fleck, R.M. McMeeking and V.S. Deshpande (2020), Dendrites as climbing dislocations in ceramic electrolytes: initiation of growth, Journal of Power Sources, 456, 227989.
There is considerable current interest in solid-state Li-ion batteries with ceramic electrolytes being extensively investigated. However, short-circuiting of such batteries by dendrite formation and growth is consistently observed for most single-ion conductor ceramic electrolytes. No coherent mechanism has to-date been proposed to explain these observations. Here, Deshpande presented a comprehensive combined electro-chemo-mechanical treatment with many novel features that not only explains the process of dendrite growth but also make predictions that are consistent with measured values of the critical current densities. This provides key insights to improve the performance of these batteries.
5. S.S. Shishvan, N.A. Fleck, and V.S. Deshpande (2021), The initiation of void growth during stripping of Li electrodes in solid electrolyte cells, Journal of Power Sources, 488, 229437.
The first step to short-circuiting of solid-state Li-ion batteries is by dendrite formation is the initiation and growth of voids in the Li electrode during the stripping phase. No coherent mechanism had been proposed to explain the formation of these voids. In this study Deshpande showed that the usual Butler-Volmer interface kinetics predicts that such voids cannot form. Following on he developed a comprehensive combined electro-chemo-mechanical treatment of Li electrode/solid electrolyte interactions. The treatment has many novel features including a modification to Butler-Volmer kinetics to account for power-law creep within the Li. The study thereby provided electrochemical and mechanistic insights into void formation in such Li-ion cells which are proving invaluable to improving the design of such cells.
6. A.J.D. Shaikeea, H. Cui, M. O’Masta, X. Zheng and V.S. Deshpande (2022), The toughness of mechanical metamaterials, Nature Materials, 21, 297-304.
In this recent article, Deshpande has uncovered the fundamental laws of failure in mechanical architected/metamaterials. This was achieved via a combination of additive manufactured metamaterial samples with millions of unit cells printed by a large area high resolution additive manufacturing technique, a range of loading conditions and detailed in-situ X-ray tomography all combined with very large-scale numerical simulations (more than 100 billion degrees of freedom).
7. P. Indurkar, A.J.D. Shaikeea, Z. Xu, H. Cui, X. Zheng and V.S. Deshpande (2022), The coupled strength and toughness of interconnected and interpenetrating multi-material gyroids, MRS Bulletin (Impact Section), 47. 461-473.
The integration of materials and architectural features at multiple scales into mechanics gave us structural designs such as the Eiffel Tower. The explosion of additive manufacturing methods has opened new avenues for the invention of light and strong mechanical metamaterials. More recently, manufacturing methods have enabled the invention of multi-material micro-architected materials that simultaneously possess high strength and toughness at a low density, and thereby can fill the so-called white spaces in the Ashby strength-toughness space. The idea is to construct three-dimensional materials with a network of crack arrestors like in rip-stop nylon and break the link between toughness and strength prevalent in most engineering materials. Here Deshpande used interconnected and interpenetrating double gyroids comprising ductile and brittle phases as an exemplar to investigate the opportunities of such designs. He demonstrated that, unlike commonly presumed in the literature, from a perspective based solely on strength and toughness, multi-material micro-architectures cannot outperform their single material counterparts at a given relative density. This holds although the interpenetrating lattices exhibit all expected toughening mechanisms like crack tip plasticity and crack flank bridging. These findings have far-reaching implications for guiding the search of lightweight architected materials that lie in the white spaces in the Ashby strength-toughness maps.
8. S. Das, A. Ippolito, J.P. McGarry and V.S. Deshpande (2022), Cell reorientation on a cyclically strained substrate, Proceedings of the National Academy of Science, Nexus, 1, 1-15.
Cyclic loadings that cells experience in vivo are known to be important for cells to maintain their physiological responses. In turn, cyclic loading is critical in developing in vitro tissue engineering strategies. However, the mechanisms of cyclic strain avoidance have remained unclear. Here Deshpande developed a non-equilibrium statistical mechanics framework that couples the mechanobiochemistry of the cytoskeletal structure with cell morphology. With the cells constrained to maintain a homeostatic state, he demonstrated that, in line with observations, cell reorientation perpendicular to the cyclic strain rather than cytoskeletal reorganization is the primary mechanism of cyclic strain avoidance. Moreover, consistent with the physiological importance of cyclic loading the model predicts that cyclic loading induces the cell morphologies to become more deterministic. These novel findings not only provide critical insights into the bio-chemo-mechanical mechanisms of cyclic strain avoidance but also give a predictive multi-scale computational tool that spans from the subcellular cytoskeletal structure to cell morphology.
9. S. AlMahri, I. Grega, A.J.D. Shaikeea, H.N.G. Wadley and V.S. Deshpande (2023), Underexcitation prevents crystallization of granular assemblies subjected to high-frequency vibration, Proceedings of the National Academy of Sciences, 120 (29) e2306209120.
Crystallisation of granular assemblies is a crucial step in numerous manufacturing methods but the fundamentals of this is remarkably poorly understood. It is well-established that there exists an optimal frequency to maximise crystallization and the literature has hypothesised that high frequency vibration inhibits crystallization because of overexcitation of the assembly akin to formation of an amorphous liquid at high temperatures due to Brownian motion. Here, rather counter-intuitively, Deshpande showed that the opposite is true --- high frequency vibration under-excites the granular assembly. Using interrupted X-ray computed tomography and high-speed photography, we demonstrate that at high frequencies momentum transfer into the bulk of the assembly is prevented by the formation of a fluidised boundary layer which results in under-excitation. Direct numerical simulations support these observations and provide further mechanistic insights that has enabled us to design a simple procedure to prevent this under-excitation and thereby allow crystallisation to occur at high frequencies. These findings not only have fundamental scientific value but also provide a pathway to help increase the rate of the crystallisation and thereby manufacturing rate in a wide range of powder technology applications as well as open routes for the large-scale manufacture of self-assembled architected materials.
10. C.S. Ha, D. Yao, Z. Xu, C. Liu, D. Elkins, M. Kile, V.S. Deshpande, Z. Kong and X. Zheng (2023), Rapid Inverse Design of Metamaterials based on Prescribed Mechanical Behavior through Machine Learning, Nature Communications, 14, 5765.
An engineering stress-strain curve records the full mechanical behaviours of a material subject to loading, which includes elasticity, yielding, fracture, strain hardening, toughness, energy absorption, and recoverability. Current paradigm in design and manufacturing via designed 3D micro-architectures relies on finding topologies that meets pairs of target mechanical properties (e.g., strength and stiffness). Here Deshpande working with his collaborators developed a machine-learning based rapid inverse design and manufacturing methodology to create a material with prescribed mechanical behaviours. As an outcome they demonstrated rapid design and printing of sporting goods comprised of architected materials with graphically tailored engineering stress-strain curves that incorporates post yielding, multiple peak stress and programmed energy absorptions. Several broad, unprecedented scientific and engineering breakthroughs stand out from this work with most importantly the inverse design method transcending the current design and manufacturing paradigm that relies on labour-intensive, iterative design processes requiring the prior expert knowledge. It is already being adopted by a broad user base with a desktop 3D printer machine and other printable materials.
