Research

The research in the group is focused on:

 

 

  • Physics of Viruses: Viruses are astounding biological particles with remarkable physical properties. In their simplest form they are just constituted by the genetic material (DNA or RNA) and a protective protein shell, or capsid. Our research focuses on the characterization of the different viral architectures and their mechanical properties from physical principles. In addition, we study the self-assembly of viral capsids and the different mechanisms of encaspulation and delivery of the genetic material.

 

  • Nucleation is the starting mechanisms behind most first-order phase transitions such as crystallization, condensation, or melting. This initial step of the phase transition has a tremendous influence on the growth dynamics and final structure of the emerging new phase. We study nucleation using molecular simulations and theory in collaboration with experimental groups.

 

  • Nano-Bio Systems. We started collaborating with experimentalists to understand the complex behavior of nanoparticles interacting with biological systems and the effect of interfaces and nanoconfinement on water-mediated interactions. This studies are relevant for nanotoxicology and have possible applications in nanomedicine.

 

  • Water and Anomalous Liquids. We study the thermodynamics and dynamics of water and other anomalous liquids. We are interested in elucidating how the many-body interactions in water (hydrogen bond cooperativity) affect its behavior. Recent experiments have confirmed our theoretical predictions on the effect of pressure on the dynamics of supercooled water.

 

  • Liquid-Liquid Phase Transition in Systems with No Anomalies. An intriguing new phenomenon that we are contributing to understand is the liquid-liquid phase transition. Surprisingly, we showed the possibility of a liquid-liquid phase transition in systems without anomalous density behavior, and also how this property depends on the details of the substance. These results are relevant for a number of systems, including protein solutions, colloids, and liquid metals. Possible applications of this discovery go from the improvement of the protein crystallization process (essential for protein analysis), to the development of new self-assembly nanoscopic particles, to a better use of complex liquids as lubricants or refrigerants and in food technology.

 

  • Glass Transition and Energy Landscape. A large number of systems, including liquids--and water, in particular--, amorphous solids, colloids, spin glasses, are characterized by very slow dynamics under specific conditions. Concepts like the Energy Landscape have been revealed to be very powerful in unifying the phenomenology of these different systems. We focus on some specific systems, such as water and frustrated spin systems, in search for universal behaviors that could help us to disclose the relevant mechanisms ruling the glass transition. The findings in this field are potentially important in food technology and pharmaceutical applications where to understand how to stabilize the glassy state is a central issue.

 

  • Radiative energy exchange at the nanoscale is an up-to-date topic of great interest and enthusiastic debate in photonic science due to its applications in nanodevices. Several experiments have been reported showing a dramatic enhancement of radiative heat through a micrometric gap in comparison to the well-known blackbody radiation limit. However, the theoretical basis used to explain these experiments are incomplete, despite of to provide an appropriate magnitude in the gap range of the experiments. Currently, near-field heat transfer is described through evanescent surface waves in the framework of classical electromagnetic theory under the implicit assumption of the fluctuation-dissipation theorem at the nanoscale. This description, however, leads to divergences in the heat flux. Moreover, the assumption that the fluctuation-dissipation theorem is satisfied at the nanoscale is precluded by quantum mechanics. The above mentioned difficulties are overcome by considering that the bulk matter intervenes in a crucial way in the radiative heat exchange process in nanogaps separating neighboring nanostructures. Thus, through our work we are promoting a conceptual change in the description of radiation phenomena at the nanoscale.

 

  • Mechanical properties of curved particle shells. Fullerene-like structures, such as colloidosomes, composite particles, and hollow particle shells offer new opportunities for drug encapsulation and delivery. Because of their small scale and topological features, the mechanical properties of these structures are special. We investigate the microstructural processes underlying the deformation of  these curved structures under different loading conditions. The ground state of spherical crystals contains a finite number of topological defects that accommodate some of the stress induced by curvature. We study their dynamic behavior and mechanical implications under driving conditions.

    "The Corbino disk geometry": Simulations of two-dimensional vortex crystals at low temperature show that laminar flow can occur in a crystal without melting: the crystal retains most of its ordered structure. This process is made possible by a suitable arrangement of topological defects in the lattice such as disclinations and dislocations. Curvature demands disclination migration while dislocations form radial walls or scars, yielding an intriguing analogy between a sheared crystal in flat space and an equilibrium crystal in curved space.

 

  • Irreversible deformation below the microscale.  Over the last years, the introduction of microcrystal compression testing has led to a deeper investigation of scale-induced phenomena in plastic deformation.  Accessing the microscale showed that size effects may have dramatic consequences on yield, making smaller samples harder to deform and more unpredictable.
    We address two fundamental questions posed by nanomechanics: the influence of sample size and geometry on the yielding properties of crystalline materials below the micrometer scale, and the characteristics of dislocation motion and energy dissipation along the deformation process.

 

  • Collective dislocation dynamics and the yielding transition. Crystalline solids such as metals deform and flow, if loaded above the yield stress, through the collective motion of dislocations. Should the external loading be smaller, the plastic deformation - or the movement of the  dislocations - comes eventually to a stop. The dislocations resist collectively the applied stress, and as a result the material "hardens" or deforms more slowly. This kind of jamming arises from the complex mutual long-range interactions. Using simulations of a dislocation dynamics model, we study the characteristics of the dynamic phase transition separating the flowing and jammed states.

 

  • Depinning and irreversible flow of topologically defected manifolds. The non-equilibrium depinning transition and driven dynamics characteristic of several disordered systems of interest, such as vortex lattices in type II superconductors, changes dramatically if the nucleation and motion of distinct types of topological defects is possible. We investigate the close relation between topological readjustments of the vortex lattice and its electrodynamic response after tuning certain relevant parameters, namely the magnetic field, the density of defects and, most importantly, the typical disorder strength, or pinning force.