Prey Impact Localization Enabled by Material and Structural Interaction in Spider Orb Webs

Spider webs are mechanical systems able to deliver an outstandingcompromise between distinct requirements such as absorbing impacts andtransmitting information about vibration sources. Both the frequencyinformation and amplitude of input signals can be used by the spider toidentify stimuli, aided by the mechanical filtering properties of orb webs. Inthis work, a numerical model based on nonlinear stress–strain constitutiverelations for spider silk is introduced to investigate how the spider orb weballows spiders to detect and localize prey impacts. The obtained resultsindicate how the orb web center relative transverse displacements, producedby local resonance mechanisms, are used for precise localization, whilenonlinear stress stiffening effects improve prey sensing. Finally, it is alsoshown that, although beneficial, a large number of radial threads may not benecessary for prey localizatio

Thermal influence on physico-chemical properties of metakaolin/organic-based geopolymers

Abstract. The high amount of organic and inorganic wastes has increased the attention to new strategies aiming to reduce the waste disposals. Among the different technologies, the geopolymers had been proposed as a powerful technology able to incorporate various kind of wastes [1]. Pure metakaolin and a mixture obtained by adding 10% of tomato waste-derived were consolidated by alkali activation at room temperature, 40 and 60°C. FT-IR spectra confirmed the geopolymerization occurrences. Conductivity and pH were evaluated at different time. The integrity tests assessed the resistance of the synthesized geopolymers and the presence of tomato-wastes led to a release of yellow organic hydro-soluble compound. Weight loss confirmed the integrity test, indeed there were no differences at 16 and 30 days. Finally, the antibacterial properties of the synthesized geopolymers were investigated [2]. References [1] H.K. Tchakouté, C.H. Rüscher, S. Kong, E. Kamseu, C. Leonelli, Constr Build Mater. 2016, 114, 276 – 289 [2] G. Dal Poggetto, M. Catauro, G. Crescente, C. Leonelli, Polymer. 2021, 13, 149

Thermal Influence on Physico-Chemical Properties of Geopolymers Based on Metakaolin and Red Tomato Waste

The high amount of organic and inorganic wastes has increased the attention to new strategies aiming to reduce the waste disposals. Organic wastes, such as tomato wastes (TWs), are a good source from which the red color can be obtained. Among the different technologies, the geopolymers had been proposed as a powerful technology able to incorporate various kinds of wastes. In this paper, pure metakaolin and a mixture obtained by adding 10% of red TW-derived (peels) are consolidated by alkali activation at room temperature, 40 and 60°C without the pigment extraction. Fourier-transform infrared (FTIR) spectra confirmed the geopolymerization occurrences. Moreover, the obtained materials are analyzed for their conductivity and pH after the sample extractions at different times. The integrity tests assessed the resistance of the synthesized geopolymers and the presence of red tomato-wastes led to a release of yellow organic hydro-soluble compounds. Finally, the weight loss confirmed the integrity test. Indeed, there are no differences at 16 and 30 d

Prey localization in spider orb webs using modal vibration analysis

Spider webs are finely tuned multifunctional structures, widely studied for their prey capture functionalities such as impact strength and stickiness. However, they are also sophisticated sensing tools that enable the spider to precisely determine the location of impact and capture the prey before it escapes. In this paper, we suggest a new mechanism for this detection process, based on potential modal analysis capabilities of the spider, using its legs as distinct distributed point sensors. To do this, we consider a numerical model of the web structure, including asymmetry in the design, prestress, and geometrical nonlinearity effects. We show how vibration signals deriving from impacts can be decomposed into web eigenmode components, through which the spider can efficiently trace the source location. Based on this numerical analysis, we discuss the role of the web structure, asymmetry, and prestress in the imaging mechanism, confirming the role of the latter in tuning the web response to achieve an efficient prey detection instrument. The results can be relevant for efficient distributed impact sensing applications

Prolate and temperature-responsive self-assemblies of amphiphilic random copolymers with perfluoroalkyl and polyoxyethylene side chains in solution

Two amphiphilic random copolymers, PEGMAx-co-FAy (x = 90 and 70 mol%), were synthesized by ATRP and their solutions were investigated as a function of solvent, concentration and temperature by DLS and SANS analyses. Both copolymers self-assembled in nanostructures by single-chain folding in water solutions over a wide range of temperatures. The values of the DLS hydrodynamic radius and the SANS radius of gyration were found to be ~4 nm and ~3.4–3.7 nm, respectively. Moreover, SANS showed the self-folded nanoassemblies to be prolated spheroids with ratio of polar/equatorial axes ~5:1 for PEGMA90-co-FA10 and ~2:1 for PEGMA70-co-FA30. On heating above a critical temperature Tc, multi-chain microassemblies were formed that reverted back to nanoassemblies on cooling below Tc. This temperature-responsive transition was fully and sharply reversible