An experimental study on adhesive or antiadhesiveand strong bio-inspired nanomaterials

This experimental PhD thesis presents the results of research performed in five different facilities: in the Laboratory of Bio-inspired Nanomechanics "Giuseppe Maria Pugno" at the Politecnico of Torino, the "Nanofacility Piemonte" at the INRIM Institute in Torino, the Division of Dental Sciences and Biomaterials of the Department of Biomedicine at the University of Trieste, the Physics Department of the Politecnico of Torino, the Toscano- Buono Veterinary Surgery in Torino and the Department of Human and Animal Biology at the University of Torino. The adhesive abilities of insects, spiders and reptiles have inspired researchers for a long time. All these organisms present outstanding performance particularly for force, adhesion and climbing abilities, especially considering their size and weight. Scientists have focused attention on the gecko's adhesive paw system and climbing abilities, and its adhesion mechanism has been an important topic of research for nearly 150 years. However, certain phenomena about geckos are still not completely understood and nowadays these still represent the main challenge of several scientific discussions which aim to better understand the gecko's adhesive ability. This thesis deals first with the influence of surface roughness on the gecko's adhesion on the inverted surface of Poly(methyl meth-acrylate) (PMMA) and glass in Chapter 1, of PMMA with different surface roughness in Chapter 2, while Chapter 3 deals with the gecko's maximum normal adhesive force and Chapter 4 looks at the optimal adhesion angle at different hierarchical levels. The gecko's moult (Appendix 1) is examined in a preliminary way. The Tokay gecko (Gekko gecko) is the most studied gecko among more than 1050 Gekkonid lizard species in the world, due to its strong adhesive ability. Because this thesis reports clear experimental measurements on two living Tokay geckos, it is comparable to scientific results reported in the literature. It is well known how small insects can carry many times their own weight and can walk quickly, but their most interesting ability is their extremely high adhesion. In recent decades, many scientists have studied a number of insects in order to understand and measure their adhesive abilities. Biological adhesion can be obtained through different adhesive mechanisms (e.g. claw, clamp, sucker, glue, friction). In particular, this thesis focuses on living specimens of the non-climbing cockroach (Blatta Orientalis Linnaeus) by evaluating its maximum shear safety factor on artificial surfaces using a centrifuge machine, see Chapter 5. In general, the adhesive structure and mechanism of an animal could be connected to the micro-structured roughness of natural substrata (e.g. plant surfaces), which animals usually find when they move around in the natural environment. In nature, plants show an extraordinary variety of morphologies and surface structures. Some plants possess two special properties; superhydrophobicity (or water-repellency) and self-cleaning (or dirt-freedom). These two related phenomena were observed for the first time by Aristotle more than 2,000 years ago but it was only in the 20th century that scientists examined them accurately on some natural leaves, e.g. the lotus (Nelumbo nucifera) on which "raindrops take a clear, spherical shape without spreading, which probably has to be ascribed to some kind of evaporated essence", as Goethe described in 1817. Accordingly to scientific literature, a strong influence of surface roughness on wettability and self-cleaning behaviour clearly emerges. This well-defined problem was of particular interest (for the Indesit Company) since we wanted to find an industrial solution which would leave the internal sides of refrigerators clean from condensed water or dirt. For this reason, a collaborative project started. Two industrial processes, plasma and thermoforming treatments, were applied to polystyrene surfaces. The Indesit refrigerator box is made of polystyrene. The influence of these industrial treatments on the surface wettability were analysed, see Chapter 6. The focus of the Indesit Company was to understand the role of roughness and to produce a superhydrophobic and self-cleaning surface. Thus, this thesis reports the method which we developed in order to design an artificial biomimetic superhydrophobic polystyrene surface, copying the natural lotus leaf (Chapter 7). In addition, surface roughness implies a modification of the tribological and frictional properties, so it assumes a crucial role when designing two contacting surfaces, in particular at nano-scale (Chapter 8). The nanometer scale characterises this thesis and is involved in everything from gecko spatulae to the waxy nanotubules of the lotus leaf, to the fibroin protein materials which constitute spider silks. In general, spider silks display superior mechanical properties but, only in the last few decades, reserachers have studied various types of silks and have evaluated their very different mechanical properties. The fact that the mechanical behaviour of spider silks varies accordingly to their type is well-known, since silk properties have been demonstrated to be species-specific and are linked to silk-based peptide fibrils or protein aggregates, with different structural and mechanical properties. The dragline silk (or radial silk) and the flag silk (or circumferential silk) of orb weaving spiders have been characterized in scientific literature while, to our knowledge, few studies have been conducted on bundles, which connect the cocoons of Meta menardi to the ceiling of caves. These were tested to determine their mechanical properties in terms of stress, strain and toughness (Chapter 9

An Experimental Study on Adhesive or Anti-adhesive, Bio-inspired Experimental Nanomaterials

Adhesive abilities of insects, spiders and reptiles have inspired researchers for a long time. All these organisms show outstanding performance, particularly for force, adhesion and climbing abilities, relative to their size and weight. Scientists have focused on the gecko’s adhesive paw system and climbing abilities. Its adhesion mechanism has been an important topic of research for nearly 150 years. However, certain phenomena of geckos are still not fully understood and represent today the main challenge in several scientific discussions that aim to better understand their adhesive ability. The manuscript deals with the influence of surface roughness on the gecko’s adhesion on the inverted surface of Poly(methyl meth-acrylate) (PMMA) and glass, of PMMA with different surface roughness, on the gecko’s maximum normal adhesive force. In general, the adhesive structure and mechanism of an animal could be connected to the micro-structured roughness of natural substrata (e.g. plant surfaces) in the natural environment. This manuscript focuses on the nanometer scale, which is involved in everything from gecko spatulae to the waxy nanotubules of the lotus leaf, to the fibroin protein materials that constitute spider silks. In general, spider silks display superior mechanical properties, but only in the last few decades, researchers investigated various types of silks and evaluated their very different mechanical properties. The dragline and the flag silks (or radial and circumferential) of orb weaving spiders have been characterized in scientific literature while, to our knowledge, few studies have been conducted on bundles, which connect the cocoons of Meta menardi to the ceiling of caves

Silk reinforced with graphene or carbon nanotubes spun by spiders

Here, we report the production of silk incorporating graphene and carbon nanotubes directly by spider spinning, after spraying spiders with the corresponding aqueous dispersions. We observe a significant increment of the mechanical properties with respect to the pristine silk, in terms of fracture strength, Young's and toughness moduli. We measure a fracture strength up to 5.4 GPa, a Young's modulus up to 47.8 GPa and a toughness modulus up to 2.1 GPa, or 1567 J/g, which, to the best of our knowledge, is the highest reported to date, even when compared to the current toughest knotted fibres. This approach could be extended to other animals and plants and could lead to a new class of bionic materials for ultimate applications

Políticas de ensino superior na pandemia: repertórios de contingência

El surgimiento de la enfermedad causada por el coronavirus a fines de 2019 y su rápida capacidad de propagación, llevó en pocos meses al mundo a una situación de crisis generalizada. Las características globalizadas del sistema mundial condujeron en efecto dominó a una tensión límite a los sistemas de salud y económicos, que obligó a los gobiernos a tomar medidas de carácter efectivo y urgente. El distanciamiento social como principal medida para el control de contagios afectó la cotidianidad de la vida en todos los niveles. El presente trabajo realiza un análisis exploratorio de tipo comparado de las estrategias relativas a la Educación Superior que surgen en el marco de esta pandemia. Se basa en la realización de un análisis documental de iniciativas en 23 países de cuatro subregiones de América, Europa y Asia. Los datos obtenidos son analizados alrededor de tres ejes: tipo de iniciativas, impacto buscado por las mismas y tipo de organismo que las promueve. El artículo introduce finalmente algunas conclusiones y plantea unas primeras discusiones que tienen origen en los resultados obtenidos.The emergence of the disease caused by the coronavirus in late 2019 and its rapid rate of spread capacity brought the world into a situation of general crisis in a few months. The globalized characteristics of the world system allowed a ripple effect on health and economic systems leading them into a limit point situation forcing governments to take effective and urgent action. Social distancing as the main measure of infection control affected everyday life at all levels. The present work carries out a comparative exploratory analysis of the strategies related to higher education that arise in the context of this pandemic. It is based on a documentary analysis of initiatives in 23 countries across four sub-regions of America, Europe and Asia. The data obtained are analyzed around three axes: type of initiatives, impact sought by them and type of organization promoting them. The article finally introduces some conclusions and raises some first discussions that have their origin in the results obtained.O surgimento da doença causada pelo coronavírus no final de 2019 e sua rápida capacidade de propagação levaram o mundo a uma situação de crise generalizada em poucos meses. As características globalizadas do sistema mundial conduziram a uma tensão limite aos sistemas de saúde e econômicos, forçando os governos a tomar medidas de caráter efetivo e urgente. O distanciamento social como principal medida para o controle de contágios afetou a cotidianidade da vida em todos os níveis. O presente trabalho realiza uma análise exploratória de tipo comparado das estratégias relativas ao Ensino Superior que surgem no âmbito desta pandemia. Baseia-se na realização de uma análise documental de iniciativas em 23 países de quatro sub-regiões da América, Europa e Ásia. Os dados obtidos são analisados em torno de três eixos: tipo de iniciativas, impacto buscado por elas, e tipo de organismo que as promove. O artigo introduz finalmente algumas conclusões e apresenta as primeiras discussões que têm origem nos resultados obtidos.publishedVersionFil: Astur, Anahí. Ministerio de Educación. Secretaría de Políticas Universitarias; Argentina.Fil: Flores, Emiliano. Ministerio de Educación. Secretaría de Políticas Universitarias; Argentina.Fil: Isasmendi, Gabriela. Ministerio de Educación. Secretaría de Políticas Universitarias; Argentina.Fil: Jakubowicz, Florencia. Ministerio de Educación. Secretaría de Políticas Universitarias; Argentina.Fil: Larrea, Marina. Ministerio de Educación. Secretaría de Políticas Universitarias; Argentina.Fil: Lepore, Evangelina. Ministerio de Educación. Secretaría de Políticas Universitarias; Argentina.Fil: Merega, María. Ministerio de Educación. Secretaría de Políticas Universitarias; Argentina.Fil: Pazos, Nuria. Ministerio de Educación. Secretaría de Políticas Universitarias; Argentina.Fil: Puppo, Chiara. Ministerio de Educación. Secretaría de Políticas Universitarias; Argentina

Mimicking water striders’ legs superhydrophobicity and buoyancy with cabbage leaves and nanotube carpets

In this work, we have studied the superhydrophobicity and buoyancy of two types of nanostructured surfaces: the cabbage leaf and a vertically aligned carbon nanotubes (VACNTs) carpet. The wettability of these surfaces were characterized by contact angle, tilting angle, sliding volume and sliding speed measurements. The results were correlated to the related surface topologies, which were investigated by scanning electron microscopy. Buoyancy of different surfaces has been investigated through measurements of the forces acting on the surface. Finally, we demonstrate that cabbage leaves and VACNT carpets have some common features with the water strider’s leg, better understanding the mechanisms of buoyancy related to the structural shape and size of natural or artificial nanostructures

An Experimental Study on Adhesive or Anti-Adhesive, Bio-inspired Experimental Nanomaterials

The proposed book aims to better understand some of the most challenging and disputed topics that could be found in nature, such as adhesive, anti-adhesive or strong mechanisms in plants or animals. This book offers additional knowledge to scientists, technicians, innovators and others in order to support the technology transfer from scientific research to industrialized products.Intro -- Contents -- Acknowledgements -- List of Figures -- List of Tables -- General Introduction -- Adhesive Materials -- Chapter 1 The Weibull Statistics Applied to the Adhesion Times of Living Tokay Geckos on Nanorough S -- Chapter 2 The Gecko's Optimal Adhesion on Nanorough Surfaces -- Chapter 3 Normal Adhesive Force-Displacement Curves of Living Tokay Geckos -- Chapter 4 Optimal Angles for Maximal Adhesion in Living Tokay Geckos -- Chapter 5 Observations of Shear Adhesive Force and Friction of Blatta Orientalis on Different Surfa -- Chapter 6 Plasma and Thermoforming Treatments to Tune The Bio-Inspired Wettability of Polystyrene -- Chapter 7 A Superhydrophobic Polystyrene by Replicating the Natural Lotus Leaf -- Chapter 8 Evidence of the Most Stretchable Egg Sac Silk Stalk of the European Spider of the Year Met -- Bibliography -- Final Acknowledgments -- General Conclusions -- IndexThe proposed book aims to better understand some of the most challenging and disputed topics that could be found in nature, such as adhesive, anti-adhesive or strong mechanisms in plants or animals. This book offers additional knowledge to scientists, technicians, innovators and others in order to support the technology transfer from scientific research to industrialized products.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries