Results for "L. Mahadevan"

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Elastohydrodynamics of a sliding, spinning and sedimenting cylinder near a soft wallNov 29 2014Jul 31 2015We consider the motion of a fluid-immersed negatively buoyant particle in the vicinity of a thin compressible elastic wall, a situation that arises in a variety of technological and natural settings. We use scaling arguments to establish different regimes ... More
Synchronization in a stochastic Hebbian network of phase oscillatorsApr 08 2014Apr 11 2014We investigate a generalized Kuramoto phase-oscillator model with Hebb-like couplings that evolve according to a stochastic differential equation on various topologies. Numerical simulations show that even with identical oscillators, there is a regime ... More
Models for elastic shells with incompatible strainsSep 25 2012Jan 08 2014The three-dimensional shapes of thin lamina such as leaves, flowers, feathers, wings etc, are driven by the differential strain induced by the relative growth. The growth takes place through variations in the Riemannian metric, given on the thin sheet ... More
Geometric Mechanics of Periodic Pleated OrigamiNov 27 2012Origami is the archetype of a structural material with unusual mechanical properties that arise almost exclusively from the geometry of its constituent folds and forms the basis for mechanical metamaterials with an extreme deformation response. Here we ... More
Statistical Mechanics of Developable RibbonsFeb 24 2010Jun 11 2010We investigate the statistical mechanics of long developable ribbons of finite width and very small thickness. The constraint of isometric deformations in these ribbon-like structures that follows from the geometric separation of scales introduces a coupling ... More
Reply to Comment on "Statistical mechanics of developable ribbons"Nov 09 2011Starostin and van der Heijden [arXiv:1111.2029] question the validity of the results reported in our Letter [Phys. Rev. Lett. 104, 238104 (2010)] regarding the existence of spontaneous helical structure in finite-temperature developable ribbons. According ... More
Multistability of free spontaneously-curved anisotropic stripsApr 20 2011Dec 07 2011Multistable structures are objects with more than one stable conformation, exemplified by the simple switch. Continuum versions are often elastic composite plates or shells, such as the common measuring tape or the slap bracelet, both of which exhibit ... More
Minimal surfaces bounded by elastic linesAug 02 2011May 30 2012In mathematics, the classical Plateau problem consists of finding the surface of least area that spans a given rigid boundary curve. A physical realization of the problem is obtained by dipping a stiff wire frame of some given shape in soapy water and ... More
Forced tearing of ductile and brittle thin sheetsAug 17 2011Jul 11 2014Tearing a thin sheet by forcing a rigid object through it leads to complex crack morphologies; a single oscillatory crack arises when a tool is driven laterally through a brittle sheet, while two diverging cracks and a series of concertina-like folds ... More
Generalized Erdos NumbersOct 20 2010We propose a simple real-valued generalization of the well known integer-valued Erdos number as a topological, non-metric measure of the `closeness' felt between two nodes in an undirected, weighted graph. These real-valued Erdos numbers are asymmetric ... More
A simple microscopic model for the dynamics of adhesive failureJun 28 2005Dec 27 2005We consider a microscopic model for the failure of soft adhesives in tension based on ideas of bond rupture under dynamic loading. Focusing on adhesive failure under loading at constant velocity, we demonstrate that bi-modal curves of stress against strain ... More
Neuromimetic Circuits with Synaptic Devices based on Strongly Correlated Electron SystemsNov 15 2014Strongly correlated electron systems such as the rare-earth nickelates (RNiO3, R = rare-earth element) can exhibit synapse-like continuous long term potentiation and depression when gated with ionic liquids; exploiting the extreme sensitivity of coupled ... More
Dynamic instability of a growing adsorbed polymorphic filamentJul 27 2011The intermittent transition between slow growth and rapid shrinkage in polymeric assemblies is termed dynamic instability, a feature observed in a variety of biochemically distinct assemblies including microtubules, actin and their bacterial analogs. ... More
Microtubules soften due to cross-sectional flatteningJul 23 2018We use optical trapping to continuously bend an isolated microtubule while simultaneously measuring the applied force and the resulting filament strain, thus allowing us to determine its elastic properties over a wide range of applied strains. We find ... More
Flutter of a FlagFeb 27 2004We give an explanation for the onset of wind-induced flutter in a flag. Our theory accounts for the various physical mechanisms at work: the finite length and the small but finite bending stiffness of the flag, the unsteadiness of the flow, the added ... More
Scale and Nature of Sulcification PatternsNov 07 2011Jul 17 2012Sulci are surface folds commonly seen in strained soft elastomers and form via a strongly subsubcriticalcritical, yet scale-free instability. Treating the threshold for nonlinear instability as a nonlinear critical point, we explain the nature of sulcus ... More
Unfolding the SulcusAug 04 2010Mar 11 2011Sulci are localized furrows on the surface of soft materials that form by a compression-induced instability. We unfold this instability by breaking its natural scale and translation invariance, and compute a limiting bifurcation diagram for sulcfication ... More
Optimal switching strategies for stochastic geocentric/egocentric navigationDec 18 2015Animals use a combination of egocentric navigation driven by the internal integration of environmental cues, interspersed with geocentric course correction and reorientation, often with uncertainty in sensory acquisition of information, planning and execution. ... More
Elastohydrodynamics and kinetics of protein patterning in the immunological synapseMay 26 2015The cellular basis for the adaptive immune response during antigen recognition relies on a specialized protein interface known as the immunological synapse (IS). Understanding the biophysical basis for protein patterning by deciphering the quantitative ... More
The 'Cheerios effect'Nov 27 2004Jun 25 2007Objects that float at the interface between a liquid and a gas interact because of interfacial deformation and the effect of gravity. We highlight the crucial role of buoyancy in this interaction, which, for small particles, prevails over the capillary ... More
Random sequential adsorption of spheres on a cylinderAug 14 2019Inspired by observations of beads packed on a thin string in such systems as sea-grapes and dental plaque, we study the random sequential adsorption of spheres on a cylinder. We determine the asymptotic fractional coverage of the cylinder as a function ... More
Similarity and singularity in adhesive elastohydrodynamic touchdownJul 14 2015We consider the touchdown of an elastic sheet as it adheres to a wall, which has a dynamics that is limited by the viscous resistance provided by the squeeze flow of the intervening liquid trapped between the two solid surfaces. The dynamics of the sheet ... More
Kinks, rings, and rackets in filamentous structuresApr 24 2004Carbon nanotubes and biological filaments each spontaneously assemble into kinked helices, rings, and "tennis racket" shapes due to competition between elastic and interfacial effects. We show that the slender geometry is a more important determinant ... More
Size dependence of lattice constants of semiconductor nanocrystalsFeb 11 2008We have theoretically examined the size dependence of the equilibrium lattice constant of nanocrystals of Si, GaAs and CdSe. While deviations from the bulk lattice constant are as large as 1-2% for unpassivated nanocrystals of Si, the deviations drop ... More
Collective thermoregulation in bee clustersJan 30 2013Nov 06 2013Swarming is an essential part of honeybee behaviour, wherein thousands of bees cling onto each other to form a dense cluster that may be exposed to the environment for several days. This cluster has the ability to maintain its core temperature actively ... More
Optimal control of plate shape with incompatible strain fieldsDec 22 2014A flat plate can bend into a curved surface if it experiences an inhomogeneous growth field. In this article a method is described that numerically determines the optimal growth field giving rise to an arbitrary target shape, optimizing for closeness ... More
Evaporation-driven ring and film deposition from colloidal dropletsNov 18 2014Evaporating suspensions of colloidal particles lead to the formation of a variety of patterns, ranging from a left-over ring of a dried coffee drop to uniformly distributed solid pigments left behind wet paint. To characterize the transition between single ... More
Feedback induced phase transitions in active porous mediaFeb 07 2014Flow through passive porous media is typically described in terms of a linear theory relating current fluxes and driving forces, in the presence of a prescribed heterogeneous permeability. However, many porous systems such as glacial drainage networks, ... More
Swarming, swirling and stasis in sequestered bristle-botsFeb 24 2013The collective ability of organisms to move coherently in space and time is ubiquitous in any group of autonomous agents that can move and sense each other and the environment. Here we investigate the origin of collective motion and its loss using macroscopic ... More
Persistence of strain in motor-filament assembliesJan 12 2015Crosslinked semi-flexible and flexible filaments that are actively deformed by molecular motors occur in various natural settings, such as the ordered eukaryotic flagellum, and the disordered cytoskeleton. The deformation of these composite systems is ... More
Shocks in sand flowing in a siloOct 20 2001We study the formation of shocks on the surface of a granular material draining through an orifice at the bottom of a quasi-two dimensional silo. At high flow rates, the surface is observed to deviate strongly from a smooth linear inclined profile giving ... More
Modeling DNA loops using the theory of elasticityJan 05 2003A versatile approach to modeling the conformations and energetics of DNA loops is presented. The model is based on the classical theory of elasticity, modified to describe the intrinsic twist and curvature of DNA, the DNA bending anisotropy, and electrostatic ... More
2D and Axisymmetric Incompressible Elastic Green's FunctionsJul 05 2014We compile a list of 2-D and axisymmetric Green's functions for isotropic full and half spaces, to complement our letter "Linear elasticity of incompressible solids". We also extend the isotropic exactly incompressible linear theory from our letter to ... More
Topology, geometry and mechanics of surgical Z-plastyMay 02 2019Reconstructive surgeries often use topological manipulation of tissue to minimize post-operative scarring. The most common version of this, Z-plasty, involves modifying a straight line cut into a Z-shape, followed by a rotational transposition of the ... More
Generalized Erdos Numbers for network analysisJul 15 2015In this paper we consider the concept of `closeness' between nodes in a weighted network that can be defined topologically even in the absence of a metric. The Generalized Erd\H{o}s Numbers (GENs) satisfy a number of desirable properties as a measure ... More
The Organization and Control of an Evolving Interdependent PopulationMay 08 2015Nov 07 2015Starting with Darwin, biologists have asked how populations evolve from a low fitness state that is evolutionarily stable to a high fitness state that is not. Specifically of interest is the emergence of cooperation and multicellularity where the fitness ... More
Termite mounds harness diurnal temperature oscillations for ventilationMar 19 2017Many species of millimetric fungus-harvesting termites collectively build uninhabited, massive mound structures enclosing a network of broad tunnels which protrude from the ground meters above their subterranean nests. It is widely accepted that the purpose ... More
Transitions to Nematic states in homogeneous suspensions of high aspect ratio magnetic rodsOct 19 2005Isotropic-Nematic and Nematic-Nematic transitions from a homogeneous base state of a suspension of high aspect ratio, rod-like magnetic particles are studied for both Maier-Saupe and the Onsager excluded volume potentials. A combination of classical linear ... More
Buckling instability of a thin-layer rectilinear Couette flowMar 10 2011We analyse the buckling stability of a thin, viscous sheet when subject to simple shear, providing conditions for the onset of the dominant out-of-plane modes using two models: (i) an asymptotic theory for the dynamics of a viscous plate and (ii) the ... More
Rippling Instability of a Collapsing BubbleAug 10 2000When a bubble of air rises to the top of a highly viscous liquid, it forms a dome-shaped protuberance on the free surface. Unlike a soap bubble, it bursts so slowly as to collapse under its own weight simultaneously, and folds into a striking wavy structure. ... More
Persistence of activity in noisy motor-filament assembliesJan 12 2015Long, elastic filaments cross-linked and deformed by active molecular motors occur in various natural settings. The overall macroscopic mechanical response of such a composite network depends on the coupling between the active and the passive properties ... More
Elastohydrodynamics of contact in adherent sheetsAug 25 2015Adhesive contact between a thin elastic sheet and a substrate in a liquid environment arises in a range of biological, physical and technological applications. By considering the dynamics of this process that naturally couples fluid flow, long wavelength ... More
Elasticity of an interfacial particle raftJun 29 2004Oct 11 2004We study the collective behaviour of a close packed monolayer of non-Brownian particles at a fluid-liquid interface. Such a particle raft forms a two-dimensional elastic solid and can support anisotropic stresses and strains, e.g. it buckles in uniaxial ... More
Shock driven jamming and periodic fracture of particulate raftsOct 29 2010Sep 24 2011A tenuous monolayer of hydrophobic particles at the air-water interface often forms a scum or raft. When such a monolayer is disturbed by the localized introduction of a surfactant droplet, a radially divergent surfactant shock front emanates from the ... More
Increased Network Interdependency Leads to AgingJan 27 2013Jan 31 2013Although species longevity is subject to a diverse range of selective forces, the mortality curves of a wide variety of organisms are rather similar. We argue that aging and its universal characteristics may have evolved by means of a gradual increase ... More
Differential-activity driven instabilities in biphasic active matterOct 10 2017Active stresses can cause instabilities in contractile gels and living tissues. Here we describe a generic hydrodynamic theory that treats these systems as a mixture of two phases of varying activity and different mechanical properties. We find that differential ... More
Exactly isochoric deformations of soft solidsJul 08 2014Many materials of contemporary interest, such as gels, biological tissues and elastomers, are easily deformed but essentially incompressible. Traditional linear theory of elasticity implements incompressibility only to first order and thus permits some ... More
Surface sulci in squeezed soft solidsMay 28 2014The squeezing of soft solids, the constrained growth of biological tissues, and the swelling of soft elastic solids such as gels can generate large compressive stresses at their surfaces. This causes the otherwise smooth surface of such a solid to becomes ... More
The von Karman equations for plates with residual strainFeb 11 2010We provide a derivation of the Foppl-von Karman equations for the shape of and stresses in an elastic plate with residual strains. These might arise from a range of causes: inhomogeneous growth, plastic deformation, swelling or shrinkage driven by solvent ... More
Wrinkling instability of an inhomogeneously stretched viscous sheetMar 30 2017Motivated by the redrawing of hot glass into thin sheets, we investigate the shape and stability of a thin viscous sheet that is inhomogeneously stretched in an imposed non-uniform temperature field. We first determine the associated base flow by solving ... More
The Shape and Motion of a Ruck in a RugJun 22 2009The motion of a ruck in a rug is used as an analogy to explain the role of dislocations in the deformation of crystalline solids. We take the analogy literally and study the shape and motion of a bump, wrinkle or ruck in a thin sheet in partial contact ... More
Macroscopic magnetic frustrationJul 10 2012Although geometrical frustration transcends scale, it has primarily been evoked in the micro and mesoscopic realm to characterize such phases as spin-ice liquids and glasses and to explain the behavior of such materials as multiferroics, high temperature ... More
Topology, geometry and mechanics of strongly stretched and twisted filamentsMay 02 2019Soft elastic filaments that can be stretched, bent and twisted exhibit a range of topologically and geometrically complex morphologies that include plectonemes, solenoids, knot-like and braid-like structures. We combine numerical simulations of soft elastic ... More
Persistence of a pinch in a pipeJul 13 2006The response of low-dimensional solid objects combines geometry and physics in unusual ways, exemplified in structures of great utility such as a thin-walled tube that is ubiquitous in nature and technology. Here we provide a particularly surprising consequence ... More
Fluid driven fingering instability of a confined elastic meniscusJul 02 2014Jul 18 2014When a fluid is pumped into a cavity in a confined elastic layer, at a critical pressure, destabilizing fingers of fluid invade the elastic solid along its meniscus (Saintyves, Dauchot, and Bouchaud, 2013). These fingers occur without fracture or loss ... More
The Monge-Ampere constrained elastic theories of shallow shellsNov 30 2013Motivated by the degree of smoothness of constrained embeddings of surfaces in $\mathbb{R}^3$, and by the recent applications to the elasticity of shallow shells, we rigorously derive the $\Gamma$-limit of 3-dimensional nonlinear elastic energy of a shallow ... More
The dynamics of sperm cooperation in a competitive environmentJul 02 2014Sperm cooperation has evolved in a variety of taxa and is often considered a response to sperm competition, yet the benefit of this form of collective movement remains unclear. Here we use fine-scale imaging and a minimal mathematical model to study sperm ... More
Banding, Excitability and Chaos in Active Nematic SuspensionsOct 19 2011Motivated by the observation of highly unstable flowing states in suspensions of microtubules and kinesin, we analyze a model of mutually-propelled filaments suspended in a solvent. The system undergoes a mean-field isotropic-nematic transition for large ... More
Excitable Patterns in Active NematicsNov 16 2010We analyze a model of mutually-propelled filaments suspended in a two-dimensional solvent. The system undergoes a mean-field isotropic-nematic transition for large enough filament concentrations and the nematic order parameter is allowed to vary in space ... More
Effectively Subsampled Quadratures For Least Squares Polynomial ApproximationsJan 20 2016Aug 31 2016This paper proposes a new sampling strategy for constructing polynomial chaos approximations for expensive physics simulation models. The proposed approach, effectively subsampled quadratures involves sparsely subsampling an existing tensor grid using ... More
A Unified Framework for Domain Adaptation using Metric Learning on ManifoldsApr 28 2018We present a novel framework for domain adaptation, whereby both geometric and statistical differences between a labeled source domain and unlabeled target domain can be integrated by exploiting the curved Riemannian geometry of statistical manifolds. ... More
Mechanics of Interfacial Composite MaterialsMay 25 2006Recent experiments and simulations have demonstrated that particle-covered interfaces can exist in stable non-spherical shapes as a result of the steric jamming of the interfacially trapped particles, which confers the interface with solid-like properties. ... More
How a Blister HealsFeb 02 2014We use experiments to study the dynamics of the healing of a blister, a localized bump in a thin elastic layer that is adhered to a soft substrate everywhere except at the bump. We create a blister by gently placing a glass cover slip on a PDMS substrate. ... More
A coordination-based approach to elasticity of floppy and stiff random networksJun 27 2008We study the role of connectivity on the linear and nonlinear elastic behavior of amorphous systems using a two-dimensional random network of harmonic springs as a model system. A natural characterization of these systems arises in terms of the network ... More
Elastic Platonic ShellsMay 28 2013Jun 11 2013On microscopic scales, the crystallinity of flexible tethered or cross linked membranes determines their mechanical response. We show that by controlling the type, number and distribution of defects on a spherical elastic shell, it is possible to direct ... More
Gyrification from constrained cortical expansionMar 12 2015The exterior of the mammalian brain - the cerebral cortex - has a conserved layered structure whose thickness varies little across species. However, selection pressures over evolutionary time scales have led to cortices that have a large surface area ... More
Flagellar dynamics of a connected chain of active, Brownian particlesNov 21 2012Eukaryotic flagella are active structures with a complex architecture of microtubules, motor proteins and elastic links. They are capable of whiplike motions driven by motors sliding along filaments that are themselves constrained at an end. Here, we ... More
Self-sustained lift and low friction via soft lubricationJan 12 2016Aug 04 2016Relative motion between soft wet solids arises in a number of applications in natural and artificial settings, and invariably couples elastic deformation and fluid flow. We explore this in a minimal setting by considering a fluid-immersed negatively-buoyant ... More
Surfactant Driven Fracture of Interfacial Particle RaftsSep 29 2005Feb 07 2006We investigate the dynamic fracture of a close-packed monolayer of particles, or particle raft, floating at a liquid-gas interface induced by the localised addition of surfactant. Unusually for a two-dimensional solid, our experiments show that the speed ... More
The size, shape, and dynamics of cellular blebsJun 11 2012A cellular bleb grows when a portion of the cell membrane detaches from the underlying cortex under the influence of a cytoplasmic pressure. We develop a quantitative model for the growth and dynamics of these objects in a simple two-dimensional setting. ... More
Elastic Cheerios effect: self-assembly of cylinders on a soft solidAug 05 2015A rigid cylinder placed on a soft gel deforms its surface. When multiple cylinders are placed on the surface, they interact with each other via the topography of the deformed gel which serves as an energy landscape; as they move, the landscape changes ... More
Dynamics of soft filaments that can stretch, shear, bend and twistJul 01 2016Soft slender structures are ubiquitous in natural and artificial systems and can be observed at scales that range from the nanometric to the kilometric, from polymers to space tethers. We present a general numerical approach to simulate the dynamics of ... More
Strain-induced alignment in collagen gelsJul 10 2009Collagen is the most abundant extracellular-network-forming protein in animal biology and is important in both natural and artificial tissues, where it serves as a material of great mechanical versatility. This versatility arises from its almost unique ... More
Programming shape using kirigami tessellationsDec 20 2018Kirigami tessellations, regular planar patterns formed by cutting flat, thin sheets, have attracted recent scientific interest for their rich geometries, surprising material properties and promise for technologies. Here we pose and solve the inverse problem ... More
Dynamics of growth and form in prebiotic vesiclesJan 14 2019Jul 20 2019The growth, form, and division of prebiotic vesicles, membraneous bags of fluid of varying components and shapes is hypothesized to have served as the substrate for the origin of life. The dynamics of these out-of-equilibrium structures is controlled ... More
Curvature condensation and bifurcation in an elastic shellMay 08 2006Jul 26 2006We study the formation and evolution of localized geometrical defects in an indented cylindrical elastic shell using a combination of experiment and numerical simulation. We find that as a symmetric localized indentation on a semi-cylindrical shell increases, ... More
Dynamics of growth and form in prebiotic vesiclesJan 14 2019The growth, form, and division of prebiotic vesicles, membraneous bags of fluid of varying components and shapes, served as the substrate for the origin of life. The dynamics of these out-of-equilibrium structures is controlled by physicochemical processes ... More
Computational mechanics of soft filamentsJul 01 2016Aug 16 2017Soft slender structures are ubiquitous in natural and artificial systems and can be observed at scales that range from the nanometric to the kilometric, from polymers to space tethers. We present a practical numerical approach to simulate the dynamics ... More
Programming Curvature using Origami TessellationsDec 21 2018Origami describes rules for creating folded structures from patterns on a flat sheet, but does not prescribe how patterns can be designed to fit target shapes. Here, starting from the simplest periodic origami pattern that yields one degree-of-freedom ... More
Spatial control of irreversible protein aggregationSep 10 2018Liquid cellular compartments spatially segregate from the cytoplasm and can regulate aberrant protein aggregation, a process linked to several medical conditions, including Alzheimer's and Parkinson's diseases. Yet the mechanisms by which these droplet-like ... More
Understanding the ferromagnetic insulating state in Cr doped VO$_2$Jul 30 2019Experimentally Cr doping in the rutile phase of VO$_2$ is found to stabilize a charge ordered ferromagnetic insulating state in the doping range of 10% to 20%. Its origin at 12.5% doping has been investigated using a combination of ab-initio electronic ... More
Representation Policy IterationJul 04 2012This paper addresses a fundamental issue central to approximation methods for solving large Markov decision processes (MDPs): how to automatically learn the underlying representation for value function approximation? A novel theoretically rigorous framework ... More
Twisting Graphene Nanoribbons into Carbon NanotubesJul 30 2011Feb 23 2012Although carbon nanotubes consist of honeycomb carbon, they have never been fabricated from graphene directly. Here, it is shown by quantum molecular-dynamics simulations and classical continuum-elasticity modeling, that graphene nanoribbons can, indeed, ... More
Digital instability of a confined elastic meniscusAug 13 2013Thin soft elastic layers serving as joints between relatively rigid bodies may function as sealants, thermal, electrical, or mechanical insulators, bearings, or adhesives. When such a joint is stressed, even though perfect adhesion is maintained, the ... More
Optical fiber modal noise in the 0.8 to 1.5 micron region and implications for near infrared precision radial velocity measurementsSep 13 2012Modal noise in fibers has been shown to limit the signal-to-noise ratio achievable in fiber-coupled, high-resolution spectrographs if it is not mitigated via modal scrambling techniques. Modal noise become significantly more important as the wavelength ... More
Skating on a Film of Air: Drops Impacting on a SurfaceOct 14 2011Oct 23 2011Drops impacting on a surface are ubiquitous in our everyday experience. This impact is understood within a commonly accepted hydrodynamic picture: it is initiated by a rapid shock and a subsequent ejection of a sheet leading to beautiful splashing patterns. ... More
Dynamics of evaporative colloidal patterningDec 04 2014Drying suspensions often leave behind complex patterns of particulates, as might be seen in the coffee stains on a table. Here we consider the dynamics of periodic band or uniform solid film formation on a vertical plate suspended partially in a drying ... More
Geometric localization in supported elastic strutsJun 11 2019Localized deformation patterns are a common motif in morphogenesis and are increasingly finding widespread applications in materials science, for instance as memory devices. Here we describe the emergence of spatially localized deformations in a minimal ... More
The Infrared Spectrum of Uranium Hollow Cathode Lamps from 850 nm to 4000 nm: Wavenumbers and Line Identifications from Fourier Transform SpectraJul 20 2011We provide new measurements of wavenumbers and line identifications of 10 100 UI and UII near-infrared (NIR) emission lines between 2500 cm-1 and 12 000 cm-1 (4000 nm to 850 nm) using archival FTS spectra from the National Solar Observatory (NSO). This ... More
Elastocapillary coalescence of plates and pillarsAug 04 2014When a fluid-immersed array of lamellae or filaments that is attached to a substrate is dried, evaporation leads to the formation of menisci on the tips of the plates or pillars that bring them together. Similarly, when hair dries it clumps together due ... More
How the velvet worm squirts slimeNov 06 2014The rapid squirt of a proteinaceous slime jet endows the ancient velvet worms (Onychophora) with a unique mechanism for defense from predators and for capturing prey by entangling them in a disordered web that immobilizes their target. However, to date ... More
Botanical RatchetsJun 23 2008Ratcheting surfaces are a common motif in nature and appear in plant awns and grasses. They are known to profer selective advantages for seed dispersion and burial. In two simple model experiments we show that these anisotropically toothed surfaces naturally ... More
Geometry, mechanics and electronics of singular structures and wrinkles in grapheneApr 29 2010As the thinnest atomic membrane, graphene presents an opportunity to combine geometry, elasticity and electronics at the limits of their validity. The availability of reliable atomistic potentials for graphene allows unprecedented precise simulations ... More
A simple model for nanofiber formation by rotary jet-spinningOct 07 2011Feb 12 2012Nanofibers are microstructured materials that span a broad range of applications from tissue engineering scaffolds to polymer transistors. An efficient method of nanofiber production is Rotary Jet-Spinning (RJS), consisting of a perforated reservoir rotating ... More
Geometric Mechanics of Curved Crease OrigamiJun 03 2012Jun 13 2012Folding a sheet of paper along a curve can lead to structures seen in decorative art and utilitarian packing boxes. Here we present a theory for the simplest such structure: an annular circular strip that is folded along a central circular curve to form ... More
The First Extrasolar Planet Discovered with a New Generation High Throughput Doppler InstrumentMay 10 2006We report the detection of the first extrasolar planet, ET-1 (HD 102195b), using the Exoplanet Tracker (ET), a new generation Doppler instrument. The planet orbits HD 102195, a young star with solar metallicity that may be part of the local association. ... More
Rotation of an immersed cylinder sliding near a thin elastic coatingNov 11 2016It is well known that an object translating parallel to a soft wall produces viscous stresses and a pressure field that deform the wall, which, in turn, results in a lift force on the object. Recent experiments on cylinders sliding near a soft incline ... More
Peeling from a patterned thin elastic filmApr 29 2004Inspired by the observation that many naturally occurring adhesives arise as textured thin films, we consider the displacement controlled peeling of a flexible plate from an incision-patterned thin adhesive elastic layer. We find that crack initiation ... More
Active elastohydrodynamics of vesicles in narrow, blind constrictionsMay 04 2017Dec 06 2017Fluid-resistance limited transport of vesicles through narrow constrictions is a recurring theme in many biological and engineering applications. Inspired by the motor-driven movement of soft membrane-bound vesicles into closed neuronal dendritic spines, ... More
Rotation of an immersed cylinder sliding near a thin elastic coatingNov 11 2016May 17 2017It is known that an object translating parallel to a soft wall in a viscous fluid produces hydro- dynamic stresses that deform the wall, which, in turn, results in a lift force on the object. Recent experiments with cylinders sliding under gravity near ... More