Soft Matter

Soft materials have a number of emergent properties that arise from the combination of geometry and softness, and encompass everyday materials such as the polymers, gels, powders, colloids, suspensions etc that are in us, on us and surround us. The study of these materials cuts across the traditional boundaries of solids, fluids and gases. Theoretical and experimental approaches to these problems at a macroscopic level use a combination of observational tools and ideas from continuum and statistical mechanics, and physical chemistry. We are interested in the simple properties of these complex materials with the goal of understanding their qualitative behaviors, manifest as their mechanical and transport properties, and their stability in the presence of external stimuli. We are also interested in harnessing these properties in such instances as adhesion mechanisms, locomotory designs, and various self-organized and self-assembled material systems. using experiments and theory to guide each other.

bristleOne theme is the dynamics of soft fluid-infiltrated gels, sponges and related entities. Using the theory of poroelasticity, we explained a number of anomalous experimental observations associated with the collapse of colloidal gels and provided a quantitative explanation for their failure via cracking and buckling. This led to a scaling theory for the dynamics of crack growth in fluid-infiltrated solids with applications to the dynamics of cracks in confined clay films, and explains the differential cooling-driven hexagonal patterns in geophysical formations such as Giant’s Causeway, with predictions that have been confirmed experimentally.  We also proposed a new theory for the mechanics of cytoplasm as a poroelastic material, highlighting the role of water movements in various cell processes, that have been confirmed experimentally by our experimental collaborators.

A second theme involves understanding the role of fluid lubrication in soft systems, that lead to a general theory of lubrication at soft interfaces with relevance to cartilaginous joint lubrication,  via a mechanism to generate a dynamical Reynolds bearing in soft systems with various different geometries and material combinations (elastic, poroelastic… ). We later generalized this theory to account for adhesion to understand how things become stuck, and also applied the theory to understand how carpets may fly close to a wall (motivated by the motion of skates, rays, and other rajimorphs), and recently realized experimentally by other groups.

A third theme is the mechanical behavior of ordered and disordered materials. Specific contributions include the experiments and theory for the stiffness of an ordered actin bundle, a combine experimental and theoretical study of disordered actin networks, and most recently a general theory for the mechanics of fragile random networks above and below the Maxwell isostatic critical point that uses geometric and topological ideas to derive scaling principles for the stiffness of the structures as a function of the coordination number. This has implications for a large range of soft materials such as foams, athermal polymer networks, cell biology, etc.

A recent example that links many of the themes of interest is a study of active agents, e.g. bristlebots, to mimic active matter such as cells, social insects, and flocking animals, using a combination of experiment, theory, and computation to show that it is possible to study swarming and the cooperative movement. A  generalization of these ideas provides a physical basis for an evolutionary question of how sperm cooperate in a competitive environment.

Natural and artificial microstructured materials

Related Publications

Self-Excited Motions of Volatile Drops on Swellable Sheets A. Chakrabarti, G.P-T. Choi, and L. Mahadevan, Phys Rev Lett. (2020)  124, 258002. [DOI] [View PDF] [Download PDF]
Rotation of a submerged finite cylinder moving down a soft incline. B. Saintyves, B. Rallabandi, T. Jules, J. Ault, T. Salez, C. Schonecker, H. A. Stone and L. Mahadevan, Soft Matter, (2020) 16, 4000-06.   [DOI] [View PDF] [Download PDF]
Topology, geometry and mechanics of strongly stretched and twisted filaments: solenoids, plectonemes, and artificial muscle fibers. N. Charles, M. Gazzola, L. Mahadevan Phys. Rev. Lett. (2020), 123, 208003. [DOI] [View PDF] [Download PDF]
Random sequential adsorption of spheres on a cylinder E. Memet, N.Tanjeem, C. Greboval, V. N. Manoharan and L. Mahadevan EPL127 (2019) 38004. 2019. [DOI] [View PDF] [Download PDF]
Geometric localization in supported elastic struts TCT Michaels, R. Kusters, AJ Dear, C. Storm, JC Weaver, L. MahadevanProceedings of the Royal Society A 475, 20190370. 2019. [DOI] [View PDF] [Download PDF]
Elastohydrodynamics of wet bristles, carpets and brushes. A. Gopinath and L. Mahadevan,  Proceedings of the Royal Society of London (A) , 467, 1665-1685, 2011. [View PDF] [Download PDF]
Swarming, swirling and stasis in sequestered bristle-bots. L. Giomi, N. Hawley-Weld and L. Mahadevan,  Proceedings of the Royal Society (A), (2012),  469, 20120637. [View PDF] [Download PDF]
Mechanical basis for fibrillar bundle morphology. T. Michaels, E. Memet, and L. Mahadevan, Soft Matter (2020), 16, 9306-18. [ONLINE ARTICLE] [DOI] [View PDF] [Download PDF]
Flow-driven branching in a frangible porous medium. N. Derr, D. Fronk, C. Weber, A. Mahadevan, C. Rycroft and L. Mahadevan, Phys. Rev. Lett.  (2020), 125, 158002. [DOI] [View PDF] [Download PDF]
Dynamics of poroelastic filaments,
Skotheim, J. and L. Mahadevan,  Proceedings of the Royal Society of London (A) , 460, 1995-2020 (2004).   [View PDF] [Download PDF]
The cytoplasm of living cells behaves as a poroelastic material E. Moeendarbary, L. Valon, M. Fritzsche, A.R. Harris, D.A. Moulding, A.J. Thrasher, E. Stride, L. Mahadevan, and G.T. Charras,  Nature Materials , 12, 253-261, 2013. [View PDF] [Download PDF]
Nonequilibrium scale selection mechanism for columnar jointing L. Goehring L. Mahadevan, and S. Morris,  Proceedings of the National Academy of Sciences (USA) , 106, 387, 2009. [View PDF] [Download PDF]
Animal cell hydraulics G. Charras, T. Mitchison and L. Mahadevan,  Journal of Cell Science , 122, 3233, 2009. [View PDF] [Download PDF]
Dynamics of chromatin decondensation reveals the structural integrity of a mechanically prestressed nucleus  A. Mazumder, T. Roopa, A. Basu, L. Mahadevan, and G. Shivashankar,  Biophysical Journal , 95, 3028, 2008. [View PDF] [Download PDF]
Gravitational collapse of colloidal gels S. Manley, J.M. Skotheim, L. Mahadevan, D. Weitz,  Physical Review Letters 94, 218302, 2005  [View PDF] [Download PDF]
Non-equilibration of hydrostatic pressure in blebbing cells, G. Charras, J. Yarrow, M. Horton, L. Mahadevan and T. Mitchison,  Nature , 435, 365-69. 2005. [View PDF] [Download PDF]
Dynamics of evaporative colloidal patterning
C. N. Kaplan, N. Wu, S. Mandre, J.Aizenberg, and L. Mahadevan,  Physics of Fluids  27, 092105, 2015.  [DOI] [View PDF] [Download PDF]
Evaporation-driven ring and film deposition from colloidal droplets
C. N. Kaplan and L. Mahadevan,  J. Fluid Mech . 781, R2 , 2015.  [DOI] [View PDF] [Download PDF]
Dynamics of fracture in drying suspensions E. Dufresene, D. Stark, N. Greenblatt, J. Cheng, J. Hutchinson, L. Mahadevan and D. Weitz,  Langmuir , 22, 7144, 2006. [View PDF] [Download PDF]
Dynamics of surfactant-driven fracture of particle rafts D. Vella, H-Y Kim, P. Aussillous and L. Mahadevan,  Physical Review Letters , 96, 178301, 2006. [View PDF] [Download PDF]
Shock driven jamming and periodic fracture of particulate rafts M. M. Bandi, T. Tallinen, L. Mahadevan,  Europhysics Letters Journal , 96, 36008, 2011. [View PDF] [Download PDF]
Crack street: the cycloidal wake of a cylinder ripping through a thin solid sheet,  Ghatak, A. and L. Mahadevan,  Physical Review Letters . 91, 215507, 2003. [View PDF] [Download PDF]
A geometric model for the periodic undulation of a confined adhesive crack Z. Wei and L. Mahadevan,  Soft Matter , 12, 1778-82 , 2015. [View PDF] [Download PDF]
Competing failure modes in finite adhesive pads T. Cohen, C.U. Chan, L. Mahadevan, Soft Matter 2018. [DOI] [View PDF] [Download PDF]
Peeling from a patterned thin elastic film,  Ghatak, A., L. Mahadevan, J. Yun, M. Chaudhury and V. Shenoy,  Proceedings of the Royal Society of London (A) , 460, 2725-35 (2004). [View PDF] [Download PDF]
Control of shape and size of nanopillar assembly by adhesion-mediated elastocapillary interaction S. Kang, B. Pokroy, L. Mahadevan and J. Aizenberg,  ACS-Nano , 4, 11, 6323-31, 2010. [View PDF] [Download PDF]
Self-organization of a mesoscale bristle into ordered hierarchical helical assemblies B. Pokroy, S. Kang, L. Mahadevan, and J. Aizenberg,  Science , 323, 237, 2009. [View PDF] [Download PDF]
Continuum dynamics of elastocapillary coalescence and arrest Z. Wei and L. Mahadevan,  Europhysics Letters  106, 14002, 2014. [View PDF] [Download PDF]
Elastocapillary coalescence of plates and pillars Z. Wei, T. M. Schneider, J. Kim, H.-Y. Kim, J. Aizenberg and L. Mahadevan,  Proceedings of the Royal Society (A)  471,20140593, 2015. [View PDF] [Download PDF]
Soft lubrication Skotheim, J. and L. Mahadevan,  Physical Review Letters , 92, 245509, 2004. [View PDF] [Download PDF]
Soft lubrication: the elastohydrodynamics of conforming and non-conforming contacts J. Skotheim and L. Mahadevan,  Physics of Fluids , 17, 092101, 2005. [View PDF] [Download PDF]
Self-sustained lift and low friction via soft lubrication B. Saintyves, T. Jules, T. Saleza, and L. Mahadevan  Proceedings of the National Academy of Sciences  (USA) 113:21 5847–5849, 2016. [View PDF] [Download PDF]
Elastohydrodynamics of a sliding, spinning and sedimenting cylinder near a soft wall T. Salez and L. Mahadevan,  J. Fluid Mech . 779, 181-196 2015. [View PDF] [Download PDF]
Rotation of an immersed cylinder sliding near a thin elastic coating B. Rallabandi, B. Saintyves, T. Jules, T. Salez, C. Schönecker, L. Mahadevan, and H.A. Stone,  Physical Review Fluids  2074102, 2017. [View PDF] [Download PDF]