On the Strength of the Carbon Nanotube-Based Space Elevator Cable: From Nano- to Mega-Mechanics

In this paper different deterministic and statistical models, based on new quantized theories proposed by the author, are presented to estimate the strength of a real, thus defective, space elevator cable. The cable, of ~100 megameters in length, is composed by carbon nanotubes, ~100 nanometers long: thus, its design involves from the nano- to the mega-mechanics. The predicted strengths are extensively compared with the experiments and the atomistic simulations on carbon nanotubes available in the literature. All these approaches unequivocally suggest that the megacable strength will be reduced by a factor at least of ~70% with respect to the theoretical nanotube strength, today (erroneously) assumed in the cable design. The reason is the unavoidable presence of defects in a so huge cable. Preliminary in silicon tensile experiments confirm the same finding. The deduced strength reduction is sufficient to pose in doubt the effective realization of the space elevator, that if built as today designed will surely break (according to the s opinion). The mechanics of the cable is also revised and possibly damage sources discussed

Vibrational disruption of feeding behaviors of a vector of plant pathogen

Interference with the behaviors associated to host plant recognition, and inter-and intra-specific communication of insect vectors of plant pathogens, could represent a sustainable strategy for reducing or disrupting pathogen transmission Here, we show that the transmission over a suitable host plant (sunflower) of a vibrational stimulus significantly affects the probing and feeding behavior of the spittlebug Philaenus spumarius (Hemiptera: Aphrophoridae), the main European vector of the fastidious bacterium Xylella fastidiosa. Specifically, ca. 30% of the individuals did not even attempt to probe the sunflower plants to which the stimulus was transmitted, while the remaining showed a sex-independent reduction in inges-tion of the xylem sap, i.e., P. spumarius\u2019 main food source, of ca. 67% compared to the control. Even so, the stimulus did not affect the feeding behavior when transmitted to olive plants. The possible reflection of a signal-based vector behavior disturbance on the epidemiology of X. fastidiosa, together with future research needs are discussed

Air Trapping Mechanism in Artificial Salvinia-Like Micro-Hairs Fabricated via Direct Laser Lithography

Salvinia leaves represent an extraordinary example of how nature found a strategy for the long term retainment of air, and thus oxygen, on a surface, the so-called ‘Salvinia effect’, thanks to the peculiar three-dimensional and hierarchical shape of the hairs covering the leaves. Here, starting from the natural model, we have microfabricated hairs inspired by those present on the Salvinia molesta leaves, by means of direct laser lithography. Artificial hairs, like their natural counterpart, are composed of a stalk and a crown-like head, and have been reproduced in the microscale since this ensures, if using a proper design, an air-retaining behavior even if the bulk structural material is hydrophilic. We have investigated the capability of air retainment inside the heads of the hairs that can last up to 100 h, demonstrating the stability of the phenomenon. For a given dimension of the head, the greater the number of filaments, the greater the amount of air that can be trapped inside the heads since the increase in the number of solid–air interfaces able to pin the liquid phase. For this reason, such type of pattern could be used for the fabrication of surfaces for controlled gas retainment and gas release in liquid phases. The range of applications would be quite large, including industrial, medical, and biological fields

3D Micropatterned Surface Inspired by Salvinia molesta via Direct Laser Lithography

Biomimetic functional surfaces are attracting increasing attention for their relevant technological applications. Despite these efforts, inherent limitations of microfabrication techniques prevent the replication of complex hierarchical microstructures. Using a 3D laser lithography technique, we fabricated a 3D patterned surface bioinspired to Salvinia molesta leaves. The artificial hairs, with crownlike heads, were reproduced by scaling down (ca. 100 times smaller) the dimensions of natural features, so that microscale hairs with submicrometric resolution were attained. The micropatterned surface, in analogy with the natural model, shows interesting properties in terms of hydrophobicity and air retention when submerged by water, even if realized with a hydrophilic material. Furthermore, we successfully demonstrated the capability to promote localized condensation of water droplets from moisture in the atmosphere

3d printing and testing of rose thorns or limpet teeth inspired anchor device for tendon tissue repair

Purposes. Advancements in medical technology have enabled medical specialists to resolve significant problems concerning tendon injuries. However, despite the latest improvements, surgical tendon repair remains challenging. This study aims to explore the capabilities of the current state-of-the-art technologies for implantable devices. Methods. After performing extensive patent landscaping and literature review, an anchored tissue fixation device was deemed the most suitable candidate. This design was firstly investigated numerically, realizing a Finite Element Model of the device anchored to two swine tendons stumps, to simulate its application on a severed tendon. Two different hook designs, both bio-inspired, were tested while retaining the same device geometry and anchoring strategy. Then, the applicability of a 3D-printed prototype was tested on swine tendons. Finally, the device-tendon stumps ensemble was subjected to uniaxial tensile tests. Results. The results show that the investigated device enables a better load distribution during the immobilized limb period in comparison to standard suture-based approaches, yet it still presents several design flaws. Conclusions. The current implantable solutions do not ensure an optimal result in terms of strength recovery. This and other weak points of the currently available proposals will serve as a starting point for future works on bio-inspired implantable devices for tendon repair

Design and proof of concept for multi degree of freedom hydrostatically coupled dielectric elastomer actuators with roto-translational kinematics for object handling

In this article we present an upgraded design of the existing push-pull hydrostatically coupled dielectric elastomer actuator (HC-DEA) for use in the field of soft manipulators. The new design has segmented electrodes, which stand as four independent elements on the active membrane of the actuator. When properly operated, the actuator can generate both out of plane and in-plane motions resulting in a multi-degrees of freedom soft actuator able to exert both normal pushes (like a traditional HC-DEA) and tangential thrusts. This novel design makes the actuator suitable for delicate flat object transportation. In order to use the actuator in soft systems, we experimentally characterized its electromechanical transduction and modeled its contact mechanics. Finally, we show that the proposed actuator can be employed as a modular unit to develop active surfaces for flat object roto-translation. © 2018 IOP Publishing Ltd