Maria Chiara Braidotti

Biomimetic antimicrobial cloak by graphene-oxide agar hydrogel

Antibacterial surfaces have an enormous economic and social impact on the worldwide technological fight against diseases. However, bacteria develop resistance and coatings are often not uniform and not stable in time. The challenge is finding an antibacterial coating that is biocompatible, cost-effective, not toxic, and spreadable over large and irregular surfaces. Here we demonstrate an antibacterial cloak by laser printing of graphene oxide hydrogels mimicking the Cancer Pagurus carapace. We observe up to 90% reduction of bacteria cells. This cloak exploits natural surface patterns evolved to resist to microorganisms infection, and the antimicrobial efficacy of graphene oxide. Cell integrity analysis by scanning electron microscopy and nucleic acids release show bacteriostatic and bactericidal effect. Nucleic acids release demonstrates microorganism cutting, and microscopy reveals cells wrapped by the laser treated gel. A theoretical active matter model confirms our findings. The employment of biomimetic graphene oxide gels opens unique possibilities to decrease infections in biomedical applications and chirurgical equipment; our antibiotic-free approach, based on the geometric reduction of microbial adhesion and the mechanical action of Graphene Oxide sheets, is potentially not affected by bacterial resistance.

Gamow vectors explain the shock profile

The description of shock waves beyond the shock point is a challenge in nonlinear physics and optics. Finding solutions to the global dynamics of dispersive shock waves is not always possible due to the lack of integrability. Here we propose a new method based on the eigenstates (Gamow vectors) of a reversed harmonic oscillator in a rigged Hilbert space. These vectors allow analytical formulation for the development of undular bores of shock waves in a nonlinear nonlocal medium. Experiments by a photothermal induced nonlinearity confirm theoretical predictions: the undulation period as a function of power and the characteristic quantized decays of Gamow vectors. Our results demonstrate that Gamow vectors are a novel and effective paradigm for describing extreme nonlinear phenomena.

Erratum: Biomimetic antimicrobial cloak by graphene-oxide agar hydrogel

A correction to this article has been published and is linked from the HTML version of this paper. The error has not been fixed in the paper.

Optothermal nonlinearity of silica aerogel

We report on the characterization of silica aerogel thermal optical nonlinearity, obtained by z-scan technique. The results show that typical silica aerogels have nonlinear optical coefficient similar to that of glass (≃10−12 m2/W), with negligible optical nonlinear absorption. The nonlinear coefficient can be increased to values in the range of 10−10 m2/W by embedding an absorbing dye in the aerogel. This value is one order of magnitude higher than that observed in the pure dye and in typical highly nonlinear materials like liquid crystals.

Nonlinear optics, optomechanics, and antibacterial coating by graphene oxide

Antibacterial items are one of the major queries from the medical community in the fight against medical infections. Indeed, bacteria are resistant and their multiplication and biofilm formation on devises are one of the major causes of infections. Finding antibacterial surfaces, which are biocompatible, cost-effective, not toxic, and spreadable over large and irregular surfaces, is not easy. However, we created an antibacterial cloak by laser printing of Graphene Oxide (GO) hydrogels by mimicking the Cancer Pagurus carapace. This surface provides up to 90% reduction of bacteria cells through a bacteriostatic and bactericidal effect. Indeed, Laser treating allows GO sheets gel to cut and wrap microorganisms. Our findings are confirmed by a theoretical active matter model. This new technology based on antibiotic-free biomimetic Graphene Oxide gels opens untrodden roads to the fight against infections in biomedical applications and chirurgical equipment.

Squeezing in a nonlocal photon fluid

Quantum fluids of light are an emerging tool employed in quantum many-body physics. Their amazing properties and versatility allow using them in a wide variety of fields including gravitation, quantum information and simulation. However the implications of the quantum nature of light in the nonlinear optical propagation are still missing many features. We theoretically predict classical spontaneous squeezing of a photon fluid in a nonlocal nonlinear medium. By using the so called Gamow vectors, we show that the quadratures of a coherent state get squeezed and that a maximal squeezing power exists. Our analysis holds true for temporal and spatial optical propagation in highly nonlocal regime. These results open a new scenario in quantum photon fluids and may lead to novel applications in fields like metrology and analogues of quantum gravity.

Highly non-paraxial nonlinear optics and analogs of quantum gravity

We show that some of the ideas developed to study quantum mechanics at the Planck scale can be used to describe the propagation of subwavelength beams in nonlinear media. It turns out that nonlinear optics may be useful to simulate models of quantized gravity and generalized Heisenberg principles.

Quantum Gravity Simulation and Irreversibility in Nonlinear Optics

We show that non-paraxial nonlinear optics can be described in terms of a generalized quantum mechanics that is nowadays studied in the field of quantum gravity. The key point is the so-called generalized uncertainty principle (GUP) that describes particle localization on a scale comparable with the Planck length. The GUP has one-to-one correspondence to the resolution limit of non-paraxial propagation.