606 research outputs found
Mechanics of plant fruit hooks
No full textHook-like surface structures, observed in some plant species, play an important role in the process of plant growth and seed dispersal. In this study, we developed an elastic model and further used it to investigate the mechanical behaviour of fruit hooks in four plant species, previously measured in an experimental study. Based on Euler–Bernoulli beam theory, the force–displacement relationship is derived, and its Young's modulus is obtained. The result agrees well with the experimental data. The model aids in understanding the mechanics of hooks, and could be used in the development of new bioinspired Velcro-like materials
Solving the multiple peeling and discovering a new angle for the optimal nanoadhesion of insects, spiders and geckos
No full textFunctional mechanism of biological adhesive systems described by multiple peeling approach
No full textKaolin nano-powder effect on insect attachment ability
No full textThe present study investigates under controlled conditions the effect of kaolin particle film on reduction of insect attachment ability. Two economically important polyphagous insect pests characterized by different attachment devices were tested, the Southern green stink bug Nezara viridula (Heteroptera: Pentatomidae) and the Mediterranean fruit fly Ceratitis capitata (Diptera: Tephritidae). We performed traction force experiments with females pulling on treated (covered with kaolin par- ticle film) and untreated (control) natural (leaf surfaces with different morphological traits) and artificial (hydrophilic and hydrophobic glass) surfaces. The data demonstrated that insect adhesion is heavily affected by kaolin particle film in both tested species. The degree of reduction of insect adhesion to the treated substrates compared with the untreated ones differed according to the kind of treated substrate owing to its initial wettability and morphology (presence of trichomes). To unravel the insect adhesion reduction mechanism of kaolin particle film, we evaluated the safety factor for females before and after walking on treated surfaces and analyzed under cryo-SEM the tarsal attachment devices of N. viridula and C. capitata after walking on treated surfaces. We observed contamination by the kaolin nanoflakes in both the smooth pads of the bug and the hairy pads of the fly. The present study can help to better understand the mechanism of action of kaolin particle film and can contribute to develop future physical control barriers against pest insects, particularly relevant owing to the need to reduce the negative impacts of pesticides on environment and human healt
Peeling line 2.8 km long: why does contact division in biological attachment devices enhance pull-off force
No full textAn optimised tapered shape of the terminal contact elements in biological attachment devices
No full textMany biological attachment devices of insects, spiders and geckoes consist of arrays of hairs (setae), which are terminated by contact elements of different shapes. However, the most frequently observed shape is a thin plate-like spatula. In spite of a rather wide range of sizes and thicknesses, most spatulae of different animals are not uniform but possess a gradient in thickness. The thickness of spatulae in the longitudinal section becomes gradually thinner close to the tip. This geometrical effect is numerically explained in the present paper, by using a numerical approach for modeling the van der Waals-like adhesion and friction between the contact element and the substrate. The approach suggests that the observed tapering in the thickness is useful for improving resistance to peeling. Similarly, the existing complementary tapering in the spatula width increases the strength of the detachment process
Attachment devices and the tarsal gland of the bug Coreus marginatus (Hemiptera: Coreidae)
No full textThe present ultrastructural investigation using scanning and transmission electron microscopy as well as light and fluorescence microscopy describes in detail the attachment devices and tarsal gland of the bug Coreus marginatus (L.) (Hemiptera: Coreidae). In particular, the fine structure of pulvilli reveals a ventral surface rich with pore channels, consistent with fluid emission, and a folded dorsal surface, which could be useful to enhance the pulvillus contact area during attachment to the substrate. The detailed description of the tarsal gland cells, whose structure is coherent with an active secretory function, allows us to consider the tarsal gland as the plausible candidate for the adhesive fluid production. Scolopidia strictly adhering to the gland cells are also described. On the basis of the fine structure of the tarsal gland, we hypothesise a fluid emission mechanism based on changes of the hydraulic pressure inside the gland, due to the unguitractor tendon movements. This mechanism could provide the fluid release based on compression of the pad and capillary suction, as demonstrated in other insects. The data here reported can contribute to understanding of insect adhesive fluid production, emission and control of its transport
Numerical simulations demonstrate that the double tapering of the spatualae of lizards and insects maximize both detachment resistance and stability
No full textMany biological attachment devices of
insects, spiders and geckos consist of arrays of hairs (setae), which are terminated by contact elements of different shapes.However, the most frequently observed shape is a thin plate-like spatula. In spite of a rather wide range of sizes, most spatulae of different animals are not uniform, but rather possess a gradient in thickness and width. Here we showthat the spatulae of insects and geckos become gradually thinner and wider approaching
the end. This geometrical effect is explained in the present paper, by using a numerical approach for the modelling of the van der Waals adhesion and friction between the contact elements and the substrate. The
approach suggests that the observed negative thickness gradient contributes to the improvement of the adhesion resistance, whereas the positive width gradient increases the stability of the detachment, probably a key factor in controlling the animal walking
Origin of the superior adhesive performance of mushroom-shaped microstructured surfaces
No full textThe superlative adhesive properties of some biological attachment systems, such as those of geckos, spiders, and insects, have inspired researchers from different fields (e.g. biology, physics and engineering) to conceive and design man-made microstructured surfaces that might mimic their performance. Among the several proposed designs, very recently mushroom-shaped adhesive microstructures have drawn the interest of scientists and engineers, because experiments have proved their superiority compared to other micro- and nano-structures. In this article, we explain theoretically the physical mechanism behind the enhanced adhesion of such microstructures, and provide for the first time a useful tool to predict adhesive performance depending on the geometry, mechanical properties of the material, and energy of adhesion. Our theoretical predictions are strongly supported by the available experimental data. The present study can streamline the optimisation of adhesive microstructures for industrial applications
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