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Liquid metal composites are promising soft conductors for applications in soft electronics, sensors, and soft robotics. Existing liquid metal composites usually have a high‐volume fraction of liquid metal, which not only increases the density but also the material cost. Future applications in soft electronics and robotics highly demand liquid metal composites with low density and high conductivity for large‐scale, low‐cost, lightweight, and more sustainable applications. In this work, lightweight and highly conductive composites embedded with liquid metal fiber networks are synthesized. This new paradigm of liquid metal composites consists of an interconnected liquid metal fiber network embedded in a compliant rubber matrix. The liquid metal fiber network serves as an ultra‐lightweight conductive pathway for electrons. Experiments indicate that this soft conductive composite also possesses nearly strain‐insensitive conductance and superior cyclic stability. Potential applications of the composite films as stretchable interconnects, electrodes, and sensors are demonstrated. [ABSTRACT FROM AUTHOR]

Poly(aspartic acid) (pAsp)-based fiber networks were developed via electrospinning and photo-crosslinking. Fiber networks hold the advantage that they exhibit a high surface-to-volume ratio, giving rise to a high water uptake and retention capacity, along with the ability to release moisture under desired circumstances (e.g. reduced relative humidity, mechanical pressure, etc.). Herein, polysuccinimide (PSI), the precursor of pAsp, was modified with 5-norbornene-2-methylamine to obtain crosslinkable norbornene-modified PSI (PSI-NB) with two different degrees of substitution, i.e. 19% and 46%. These derivatives were electrospun into thin uniform fibers after optimization of the processing parameters. The fiber sheets were crosslinked via a thiol-ene step-growth mechanism with three different thiol crosslinkers exploiting UV-A irradiation in the presence of TPO-L as photo-initiator. Using this strategy, fiber networks with diameters ranging between 1.27 ± 0.29 and 2.20 ± 1.05 µm were obtained, as visualized with scanning electron microscopy (SEM). Successful crosslinking was evidenced by a dissolution test in dimethylformamide and through X-ray photoelectron spectroscopy. Finally, the PSI-NB fiber networks were hydrolyzed to obtain pAsp-NB fiber networks by alkaline hydrolysis in a carbonate buffer solution, as confirmed by Fourier-transform infrared spectroscopy. The morphology of the fibers following hydrolysis was visualized by SEM and the average fiber diameters were calculated and compared to the diameters before hydrolysis, generally showing a diameter increase due to swelling of the fibers in aqueous solution. In conclusion, pAsp-based fiber networks were successfully developed and stabilized via photo-crosslinking.

The utility of auxetic materials in applications such as foams and composites is contingent upon the performance of these materials under cyclic loading. Recently, several textile materials (knitted, woven, and nonwoven fabrics) have been found to exhibit auxetic properties, either through design and/or the use of a postprocessing treatment. In the wake of these advancements, this research examines the reversibility of the out‐of‐plane auxetic response in previously studied polyester fiber needle‐punched nonwovens. Herein, a heat‐compressed nonwoven is strained cyclically to different levels, and the thickness is measured before and after straining. While axial extension is found to be elastic for up to 3% strain, thickness increases (auxetic responses) are almost completely reversible for 1% axial strain and highly reversible for 2% and 3% axial strain. Irreversible changes can be clearly observed starting at strains of 2% and larger, especially for a higher number of cycles. Combining these results with the previous understanding from microscopic and tomographic imaging, possible reversible (straightening of bent fibers and fiber bundles) and irreversible (slipping or breaking of fibers) structural deformations leading to thickness changes are identified. These processes influence the magnitude of the auxetic response within and beyond the elastic strain regime, respectively. [ABSTRACT FROM AUTHOR]

Cells residing in living tissues apply forces to their immediate surroundings to promote the restructuration of the extracellular matrix fibres and to transmit mechanical signals to other cells. Here we use a minimalist model to study how these forces, applied locally by cell contraction, propagate through the fibrous network in the extracellular matrix. In particular, we characterize how the transmission of forces is influenced by the connectivity of the network and by the bending rigidity of the fibers. For highly connected fiber networks the stresses spread out isotropically around the cell over a distance that first increases with increasing contraction of the cell and then saturates at a characteristic length. For lower connectivity, however, the stress pattern is highly asymmetric and is characterised by force chains that can transmit stresses over very long distances. We hope that our analysis of force transmission in fibrous networks can provide a new avenue for future studies on how the mechanical feedback between the cell and the ECM is coupled with the microscopic environment around the cells.

Skin undergoes mechanical alterations due to changes in the composition and structure of the collagenous dermis with aging. Previous studies have conflicting findings, with both increased and decreased stiffness reported for aging skin. The underlying structure--function relationships that drive age-related changes are complex and difficult to study individually. One potential contributor to these variations is the accumulation of nonenzymatic crosslinks within collagen fibers, which affect dermal collagen remodeling and mechanical properties. Specifically, these crosslinks make individual fibers stiffer in their plastic loading region and lead to increased fragmentation of the collagenous network. To better understand the influence of these changes, we investigated the impact of nonenzymatic crosslink changes on the dermal microstructure using discrete fiber networks representative of the dermal microstructure. Our findings suggest that stiffening the plastic region of collagen's mechanical response has minimal effects on network-level stiffness and failure stresses. Conversely, simulating fragmentation through a loss of connectivity substantially reduces network stiffness and failure stress, while increasing stretch ratios at failure. [ABSTRACT FROM AUTHOR]

This work presents a discrete-to-continuum approach to the constitutive response of composite materials formed by embedding a network of spider silk fibers in a matrix material. A multiscale model that makes use of the virial stress concept of statistical mechanics is formulated, which accounts for hyperelastic constitutive equations of the component materials. The finite element implementation of the given constitutive equations is also carried out. Numerical simulations show the response of a silk composite formed by embedding a spider orb web in a matrix material, and illustrate the main features of the proposed model. In the presence of a weak matrix, the force–displacement response of a silk composite is compared with that deriving from an atomistic modeling of the spider orb web. A simulation of the response of a composite equipped with an elastomeric matrix is also discussed. • Embedding of spider silk fibers in a matrix material. • Discrete-to-continuum modeling of spider silk composites. • Homogenization approach making use of the virial stress concept. • Finite element simulations of spider silk composite membranes. [ABSTRACT FROM AUTHOR]

Skin is a complex tissue whose biomechanical properties are generally understood in terms of an incompressible material whose microstructure undergoes affine deformations. A growing number of experiments, however, have demonstrated that skin has a high Poisson's ratio, substantially decreases in volume during uniaxial tensile loading, and demonstrates collagen fiber kinematics that are not affine with local deformation. In order to better understand the mechanical basis for these properties, we constructed multiscale mechanical models (MSM) of mouse skin based on microstructural multiphoton microscopy imaging of the dermal microstructure acquired during mechanical testing. Three models that spanned the cases of highly aligned, moderately aligned, and nearly random fiber networks were examined and compared to the data acquired from uniaxially stretched skin. Our results demonstrate that MSMs consisting of networks of matched fiber organization can predict the biomechanical behavior of mouse skin, including the large decrease in tissue volume and nonaffine fiber kinematics observed under uniaxial tension. [ABSTRACT FROM AUTHOR]

Skin undergoes mechanical alterations due to changes in the composition and structure of the collagenous dermis with aging. Previous studies have conflicting findings, with both increased and decreased stiffness reported for aging skin. The underlying structure-function relationships that drive age-related changes are complex and difficult to study individually. One potential contributor to these variations is the accumulation of nonenzymatic crosslinks within collagen fibers, which affect dermal collagen remodeling and mechanical properties. Specifically, these crosslinks make individual fibers stiffer in their plastic loading region and lead to increased fragmentation of the collagenous network. To better understand the influence of these changes, we investigated the impact of nonenzymatic crosslink changes on the dermal microstructure using discrete fiber networks representative of the dermal microstructure. Our findings suggest that stiffening the plastic region of collagen's mechanical response has minimal effects on network-level stiffness and failure stresses. Conversely, simulating fragmentation through a loss of connectivity substantially reduces network stiffness and failure stress, while increasing stretch ratios at failure., (Copyright © 2024 by ASME.)

The degree of substitution (DS) of cellulose derivative is significantly associated with its properties. In this paper, a series of quaternary cellulose (QC) samples with different DS (ranging from 0.16 to 0.51) were synthesized with assistance of microwave and their relationship with strength improvement of fiber networks was investigated systematically. QCs were characterized by elemental analysis, FT-IR, 1H NMR, and TGA, etc. The results showed that the cationic quaternary ammonium salt group was successfully grafted onto the backbones of cellulose chains and the thermal stability was associated inversely with the DS of QCs. However, the results of strength test for the fiber networks from secondary fiber of old corrugated containers showed that the tensile and burst strength was enhanced by addition of QCs, and their performance was positively correlated their DS. The best result achieved in this investigation was in the case of QC with DS of 0.51, with increments of tensile and burst strength 6.17% and 11.68%, respectively, at a dosage of 1.0 wt% based on oven-dry pulp. This investigation highlights the importance of DS of QC to its application in strength improvement for fiber networks. • QCs with different DS were synthesized with assistance of microwave. • DS of QCs was in the range of 0.16– 0.51 • The tensile and burst strength of fiber networks improved by all QCs • The best by the QC with DS of 0.51 increased 6.17% and 11.68%, respectively. • It highlighted the impacts of DS of QCs on the properties of fiber networks. [ABSTRACT FROM AUTHOR]

• The increase in network connectivity corresponds to an enhanced Poisson's ratio, signifying a strong multiaxial coupling. • The high tension-to-compression stiffness ratio and strong multiaxial coupling induce ultra-long-range force transmission. • A fibrous constitutive model is formulated to understand the mechanism of ultra-long-range force transmission. • The stress decay of cell contraction follows a scaling law (σ r ∼ r - n), with the decay exponent(n) ranging from 1.5 to 3. Force transmission in the extracellular matrix is crucial for cellular mechanosensing. This transmission is influenced by factors such as tension–compression asymmetric stiffness and the fiber alignment of fibrous materials. However, the role of the anomalous Poisson's ratio, intrinsic to fibrous materials, in force transmission remains underexplored. In this study, we utilize discrete fiber network simulations with different levels of connectivity to examine the stress decay of cell contraction in fibrous matrices. Our findings show that highly connected fiber networks exhibit reduced fiber alignment and atypical tensile hoop stress. This leads to an ultra-slow decay of radial stress induced by isotropic contraction of spherical cells. Delving deeper, we discover that the increase of network connectivity corresponds to an enhanced Poisson's ratio, signifying a pronounced multiaxial coupling effect. To fully comprehend this multiaxial coupling, we develop a constitutive law for fibrous materials. This law considers the stiffening along the tensile direction and their significant transverse contraction. Theoretical analysis elucidates that the stress decay of cell contraction adheres to a scaling law, represented as σ r ∼ r - n , with the decay exponent n ranging from 1.5 to 3. Notably, this finding diverges from prior predictions that n is more than 2. The combination of a high tension-to-compression stiffness ratio with strong multiaxial coupling leads to ultra-long-range force transmission in fibrous materials. This ultra-long-range force transmission is marked by a convergent diminishing n approximating 1.5. In summary, our study provides a quantitative framework for elucidating the maximum limit of the force transmission range and serves as a guideline for developing innovative biomimetic materials. [ABSTRACT FROM AUTHOR]

Post-processing is an essential step towards the practical deployment of physical-layer secure key distribution (SKD) in classical fiber channels. However, the comparison and combination of different post-processing methods are not explored yet. Here, we fully evaluate the post-processing protocol and analyze various combinations of quantization and information reconciliation (IR), and present the efficient solutions associated with the key entropy source between the legal parties. In addition, the SHA3-256 hash function-based privacy amplification is exploited to further enhance the robust key secrecy and randomness. The results show that, the proposed protocol significantly increases the achievable key generation rate (KGR) up to 130-205% using the combination of multi-bit adaptive quantizer and IR with syndrome-decoding LDPC, compared with the previous post-processing using the same original key waveforms extracted from physical-layer SKD. [ABSTRACT FROM AUTHOR]

Summary: The agglomeration of self-assembled fibers of π-conjugated molecules is crucial to the formation of low-molecular-weight supramolecular gels. However, identification of the in situ spectroscopic signatures of fiber agglomeration has remained a challenging endeavor. Here, we use a combination of chiroptical techniques, namely circular dichroism (CD), magnetic circular dichroism (MCD), and fluorescence-detected circular dichroism (FDCD), to investigate the agglomeration of self-assembled fibers of a chiral low-molecular-weight gelator, l-alanine-substituted perylene imide bis(n-butyl) ester (PIBE). Surprisingly, we find that agglomerated PIBE fibers exhibit an opposite CD signature in comparison to the isolated PIBE fibers. In contrast, the MCD and FDCD responses do not change during the agglomeration process, revealing that the local structure in the individual fibers is unperturbed. Using Brownian dynamics simulations, we conclude that the effective charge on the fibers dictates the agglomeration process and that the final geometry of the agglomerated fibers is marked by crossed nodes.

The unique and random physical-layer properties of optical fiber channels have been exploited for a simple and cost-effective secure key generation and distribution (SKGD). However, state-of-the-art SKGD approaches focused mainly on initial key extraction, while the post-processing protocol has to be explored to guarantee error-free operation, effective key generation rate (KGR) and high key secrecy. Here we propose a full post-processing protocol for SKGD in fiber networks. A lossy quantizer is optimized to achieve the trade-off between the KGR and key disagreement rate. The distributed source coding based information reconciliation is used to remove quantization errors. The privacy amplification is applied to improve the randomness and secrecy of the generated key using hashing functions. The post-processing protocol provides a SKGD solution of error-free, high randomness and high secrecy in fiber networks. [ABSTRACT FROM AUTHOR]

In this work, we study the mechanical behavior of non-crosslinked networks of fibers that interact adhesively. Adhesion drives fiber organization into bundles and a network of fiber bundles forms as a result of this process. Bundles split and re-connect forming specific triangular features at all bundle intersections, with role in network stabilization. The structure of such networks has been discussed in the literature, but their mechanics remains largely unexplored. We show here that such networks are exceptionally stable, and despite the absence of crosslinks between fibers behave, at relatively small strains, essentially similar to crosslinked networks, in which the role of crosslinks is played by the triangular structures at bundle intersections. We also provide new results regarding the effect of the network architecture on the type of strain stiffening observed in tension. The results apply to carbon nanotube structures, such as buckypaper, and various connective biological tissue in which collagen fibrils form bundles and the tissue is a network of collagen fibril bundles. [ABSTRACT FROM AUTHOR]

We propose an estimate for the effective elastic properties of a new imagined two-phase bi-continuous composite material type with a so-called ''pantographic-inspired" (P-I) architecture in the sense of a matrix reinforcement which is a 3D fiber network capable of large, pantographic-like, deformations, owing to particular properties carried by the fiber interconnections. Such fiber networks co-continuous with the matrix are described from an assemblage of inter-penetrated planar alignments of parallel infinite, identical and equally distant, rods or beams that we call fiber layers or FPAs for ''fiber planar alignments". Piece-wise linear deformation of such a structure is constrained, as 2D pantographs are, by the specific relations that link the evolutions of the FPA misorientations, of the fiber inter distance and concentration within each FPA, and of the given characteristics to the through-layer interconnections. We derive effective properties within a well defined first gradient elastic homogenization scheme for macro-homogeneous composite structures, based on explicating the involved mean Green operator (mGO) for the representative pattern of such a P-I networked reinforcement in an isotropic matrix. This mGO for P-I composites is built in making use of previously derived and presented mGOs for rod and beam FPAs. Comparisons with Young and shear modulus variations during numerical homogeneous extension simulations show that the proposed modeling provides relevant effective property evolutions with the advantage of being analytical. Comparing so estimated force-displacement curves with numerical ones for 2D pantographs enables to identify ways to further account in the modeling for the specific strengthening effects of the FPA interconnections in pantographs. This tends to prove such P-I composite structures, still to be manufactured, to possibly also behave similarly to pantograph ones. [ABSTRACT FROM AUTHOR]

Abstract Non-woven materials are fiber networks consolidated by different bonding techniques. It has been found that interfiber bond fracture is a major damage mechanism in non-wovens and strongly affects mechanical strength and toughness. In this article, we present a micromechanically based damage model for non-wovens. The model is built upon modeling single bond breaking processes and linking local damage events to macroscopic behaviors. In this model, a nonlinear term is introduced to describe non-affine deformation of fibers at a bond. The traction load on a bonded interface is determined by considering local force balance and network constraints. A bond breaks when its traction load exceeds a critical value, and this local information is used to update the global damage state through a classical continuum damage mechanics framework. Spatial correlation of damage in the network is modeled using a non-local averaging scheme. The proposed model is applied to a commercial non-woven series. The model is able to reproduce experimentally observed behaviors including elasticity, non-linear hardening, peak load and damage localization under uniaxial tensile loading as a function of network density. Damage states predicted by the numerical simulations match well with in-situ imaging results demonstrating the predictive capability of the model. The proposed model bridges non-woven microstructure and macroscopic behaviors and thus can serve as an effective tool for future studies of the mechanics of fiber networks. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Viscoelasticity plays an important role in the mechanical behavior of biological tissues undergoing dynamic loading. Exploring viscoelastic relaxation spectra of the tissue is essential for predicting its mechanical response. Most load-bearing tissues, however, are also composed of networks of intertwined fibers and filaments of, e.g., collagen, elastin. In this work, we show how non-affine deformations within fiber networks affect the relaxation behavior of the material leading to the emergence of structure-dependent time scales in the relaxation spectra. In particular, we see two different contributions to the network relaxation process: a material contribution due to the intrinsic viscoelasticity of the fibers, and a kinematic contribution due to non-affine rearrangement of the network when different fibers relax at different rates. We also present a computational model to simulate viscoelastic relaxation of networks, demonstrating the emergent time scales and a pronounced dependence of the network relaxation behavior on whether components with different relaxation times percolate the network. Finally, we observe that the simulated relaxation spectrum for Delaunay networks is comparable to that measured experimentally for reconstituted collagen gels by others. Statement of Significance Viscoelasticty plays an important role in the mechanical behavior of biological tissues undergoing dynamic loading. Stress relaxation tests provide a convenient way to explore the viscoelastic behavior of the material, while providing an advantage of interrogating multiple time scales in a single experiment. Most load bearing tissues, however, are composed of networks of intertwined fibers and filaments. In the present study, we analyze how the network structure can affect the viscoelastic relaxation behavior of a tissue leading to the emergence of structure-based time scales in the relaxation spectra. [ABSTRACT FROM AUTHOR]

Composites comprising included phases in a continuous matrix constitute a huge class of meta-materials, whose effective properties, whether they be mechanical, physical or coupled, can be selectively optimized by using appropriate phase arrangements and architectures. An important subclass is represented by "network-reinforced matrices," say those materials in which one or more of the embedded phases are co-continuous with the matrix in one or more directions. In this article, we present a method to study effective properties of simple such structures from which more complex ones can be accessible. Effective properties are shown, in the framework of linear elasticity, estimable by using the global mean Green operator for the entire embedded fiber network which is by definition through sample spanning. This network operator is obtained from one of infinite planar alignments of infinite fibers, which the network can be seen as an interpenetrated set of, with the fiber interactions being fully accounted for in the alignments. The mean operator of such alignments is given in exact closed form for isotropic elastic-like or dielectric-like matrices. We first exemplify how these operators relevantly provide, from classic homogenization frameworks, effective properties in the case of 1D fiber bundles embedded in an isotropic elastic-like medium. It is also shown that using infinite patterns with fully interacting elements over their whole influence range at any element concentration suppresses the dilute approximation limit of these frameworks. We finally present a construction method for a global operator of fiber networks described as interpenetrated such bundles. [ABSTRACT FROM AUTHOR]

Using particle-scale models to accurately describe property enhancements and phase transitions in macroscopic behavior is a major engineering challenge in composite materials science. To address some of these challenges, we use the graph theoretic property of rigidity to model mechanical reinforcement in composites with stiff rod-like particles. We develop an efficient algorithmic approach called rigid graph compression (RGC) to describe the transition from floppy to rigid in disordered fiber networks ("rod-hinge systems""), which form the reinforcing phase in many composite systems. To establish RGC on a firm theoretical foundation, we adapt rigidity matroid theory to identify primitive topological network motifs that serve as rules for composing interacting rigid particles into larger rigid components. This approach is computationally efficient and stable, because RGC requires only topological information about rod interactions (encoded by a sparse unweighted network) rather than geometrical details such as rod locations or pairwise distances (as required in rigidity matroid theory). We conduct numerical experiments on simulated two-dimensional rod-hinge systems to demonstrate that RGC closely approximates the rigidity percolation threshold for such systems, through comparison with the pebble game algorithm (which is exact in two dimensions). Importantly, whereas the pebble game is derived from Laman's condition and is only valid in two dimensions, the RGC approach naturally extends to higher dimensions. [ABSTRACT FROM AUTHOR]

Fiber networks are ubiquitous. The networks of interest to this study are distinguished from the widely studied planar random fiber networks (RFN) by their low areal density (grammage), preferential orientation, and fiber curl. Oriented networks are created through a high speed manufacturing process called forming in paper making. A dilute suspension of elastic fibers in water impinges on a moving wire to create a formed network. A discrete element method (DEM) based forming model is developed that incorporates the qualitative effects of fluid shear (preferred fiber orientation) and viscous drag during drainage (fiber conformation to the wire topography). Virtual tensile tests performed on thus formed networks reveal that the tensile response is initially softer due to non-affine deformation, and anisotropic due to preferential orientation. Consequently, an orientation dependent power law with a non-unique exponent emerges for the scaling of modulus and strength with the network density. Tensile test simulations reveal the re-alignment of fibers along the loading direction, and strong strain localization resulting in a few fibers (∼ 1%) carrying the imposed strain energy. Fiber curl and orientation are observed to govern the degree of non-affine response, stiffness, and strain localization, suggesting that controlling the degree of anisotropy and fiber curl offers the possibility to design networks for specific stiffness and specific strength. • Significant degree of non-affinity in low grammage networks. • Anisotropy in tensile properties and non-affinity in oriented networks. • Bending is important in networks with curled fibers. • Strain energy distribution in fiber networks is highly skewed. • Shear-lag and affine predictions do not hold for low grammage networks. [ABSTRACT FROM AUTHOR]

A handheld line information reader and a line information generator were developed for the efficient management of optical communication lines. The line information reader consists of a photo diode, trans-impedance amplifier, voltage amplifier, microcontroller unit, display panel, and communication modules. The line information generator consists of a laser diode, laser driving circuits, microcontroller unit, and communication modules. The line information reader can detect the optical radiation field of the test line by bending the optical fiber. To enhance the sensitivity of the line information reader, an additional lens was used with a focal length of 4.51 mm. Moreover, the simulation results obtained through BeamPROP® software from Synopsys, Inc. demonstrated a stronger optical radiation field of the fiber due to a longer transmission wavelength and larger bending angle of the fiber. Therefore, the developed devices can be considered as useful tools for the efficient management of optical communication lines. [ABSTRACT FROM AUTHOR]

In this paper we present algorithms for measuring local characteristics of random fiber systems. The calculation of the local directions and radii is based on directional distance transforms and evaluation of the inertia moments and axes of the resulting extremities of the centralized, directed chords. The method provides continuous results while minimizing the runtime by using few sampled directions. Furthermore several steps of improvement for the computation of orientation and radius information are presented. The algorithms are evaluated using synthetic data and applied to images of realmicrostructures obtained by computer tomography.

Low density tissue papers are soft fiber networks with a folded internal microstructure—deliberately imparted during a widely used manufacturing process, called dry creping. The folded crepe structure enhances a tissue paper's specific volume, stretchability, and softness. The influence of the micron-scale crepe structure on nonlinear tensile response is studied using experiments and a discrete elasto-plastic model (DEM). First, 'Crepe Index (CI)' is defined to quantify the crepe structure. An optical method to obtain high resolution edge images is developed to measure the CI. The relationship between the CI and tensile failure strain and initial elastic stiffness is assessed: the failure strain is observed to be proportional to CI, while the dependence of initial stiffness on CI is unclear–presumably due to the damage induced through the de-densification of fiber layers during the manufacturing. The effect of CI on initial stiffness and failure strain is assessed using DEM by idealizing the creped paper as a segmented triangular wave—each segment governed by a bilinear elastoplastic constitutive law and a strength-based failure criterion. The model reveals that the initial stiffness of a creped sheet depends not only on the CI but also on sheet-thickness to crepe-wavelength ratio, and the stiffness of the uncreped sheet. The failure strain is found to be stretching dominated at low CI, and bending dominated at higher CI. Qualitative agreement is found between the DEM and experiments. The significance of both the material and the geometric non-linearity on the macroscale tensile response of a creped tissue paper emerges from this study. • Tissue paper is a complex architected fiber network. • Imaging method is developed to visualize folded internal structure of a tissue paper at micron scale. • Nonlinear tensile response of a tissue paper originates from the folded geometry and the fiber network. • Crepe Index is introduced to quantify crepe structure and correlate with failure strain. strain. [ABSTRACT FROM AUTHOR]

Large-scale force generation is essential for biological functions such as cell motility, embryonic development, and muscle contraction. In these processes, forces generated at the molecular level by motor proteins are transmitted by disordered fiber networks, resulting in large-scale active stresses. Although these fiber networks are well characterized macroscopically, this stress generation by microscopic active units is not well understood. Here we theoretically study force transmission in these networks. We find that collective fiber buckling in the vicinity of a local active unit results in a rectification of stress towards strongly amplified isotropic contraction. This stress amplification is reinforced by the networks' disordered nature, but saturates for high densities of active units. Our predictions are quantitatively consistent with experiments on reconstituted tissues and actomyosin networks and shed light on the role of the network microstructure in shaping active stresses in cells and tissue. [ABSTRACT FROM AUTHOR]

In this study, a geographic information system (GIS)-based novel flber network monitoring system has been developed to improve the operation and maintenance of fiber optic networks (FONs). The main aim of the developed system is to provide the required capabilities for both detailed digital modeling and central monitoring of FONs. The system can perform scheduled measurements and dispatch alarms if any fault or degradation is detected in the concerned FON. It also indicates the alarm locations on a map as a considerable contribution to decreasing mean time to repair. The developed monitoring system has more security features than others. [ABSTRACT FROM AUTHOR]

To boost the deployment of fiber-to-the-home networks in order to meet the ever-increasing demand for bandwidth, there is a strong need for single-mode fiber (SMF) connectors which combine low insertion loss with field installability. Shifting from ferrule-based to ferruleless connectors can reduce average insertion losses appreciably and minimize modal noise interference. We propose a ferruleless connector and adaptor in which physical contact between two inline fibers is ensured by at least one fiber being in a buckled state. To this end, we design a buckling cavity in which the SMF can buckle in a controlled way to ensure good optical performance as well as mechanical stability. This design is based on both mechanical and optical considerations. Finite element analysis suggests that mechanically a minimal buckling cavity length of 17 mm is required, while the height of the cavity should be chosen such that the buckled SMF is not mechanically confined to ensure buckling in a first-order mode. The optical bending loss in the buckled SMF is calculated using a fully vectorial mode solver, showing that aminimal buckling cavity length of 20 mm is necessary to keep the excess optical loss from bending below 0.1 dB. Both our optical and mechanical simulation results are experimentally verified. [ABSTRACT FROM AUTHOR]

Highlights: [•] We model computationally three-dimensional random fiber networks. [•] Apparent elastic stiffness components C1111 and C1212 are computed. [•] Stiffness decreases with higher scale, orientation angle and void volume fraction. [•] Scatter decreases with higher scale, orientation angle and void volume fraction. [•] Dangling fibers influence apparent stiffness. [ABSTRACT FROM AUTHOR]

Abstract: Bonded random fiber networks are heterogeneous on multiple scales. This leads to a pronounced size effect on their mechanical behavior. In this study we quantify the size effect and determine the minimum model size required to eliminate the size effect for given set of system parameters. These include the network density, the fiber length and the fiber bending and axial stiffness. The results may guide the definition of models and the selection of the size of representative volume elements in sequential multiscale models of fiber networks. To underline the origins of the size effect, we characterize the network heterogeneity by analyzing the geometry of the network (density distribution), the strain field and the strain energy distribution. The dependence of the heterogeneity on the scale of observation and system parameters is discussed. [Copyright &y& Elsevier]

The use of a porous coating on prosthetic components to encourage bone ingrowth is an important way of improving uncemented implant fixation. Enhanced fixation may be achieved by the use of porous magneto-active layers on the surface of prosthetic implants, which would deform elastically on application of a magnetic field, generating internal stresses within the in-growing bone. This approach requires a ferromagnetic material able to support osteoblast attachment, proliferation, differentiation, and mineralization. In this study, the human osteoblast responses to ferromagnetic 444 stainless steel networks were considered alongside those to nonmagnetic 316L (medical grade) stainless steel networks. While both networks had similar porosities, 444 networks were made from coarser fibers, resulting in larger inter-fiber spaces. The networks were analyzed for cell morphology, distribution, proliferation, and differentiation, extracellular matrix production and the formation of mineralized nodules. Cell culture was performed in both the presence of osteogenic supplements, to encourage cell differentiation, and in their absence. It was found that fiber size affected osteoblast morphology, cytoskeleton organization and proliferation at the early stages of culture. The larger inter-fiber spaces in the 444 networks resulted in better spatial distribution of the extracellular matrix. The addition of osteogenic supplements enhanced cell differentiation and reduced cell proliferation thereby preventing the differences in proliferation observed in the absence of osteogenic supplements. The results demonstrated that 444 networks elicited favorable responses from human osteoblasts, and thus show potential for use as magnetically active porous coatings for advanced bone implant applications. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013. [ABSTRACT FROM AUTHOR]

Beneficial effects on bone-implant bonding may accrue from ferromagnetic fiber networks on implants which can deform in vivo inducing controlled levels of mechanical strain directly in growing bone. This approach requires ferromagnetic fibers that can be implanted in vivo without stimulating undue inflammatory cell responses or cytotoxicity. This study examines the short-term in vitro responses, including attachment, viability, and inflammatory stimulation, of human peripheral blood monocytes to 444 ferritic stainless steel fiber networks. Two types of 444 networks, differing in fiber cross section and thus surface area, were considered alongside austenitic stainless steel fiber networks, made of 316L, a widely established implant material. Similar high percent seeding efficiencies were measured by CyQuant® on all fiber networks after 48 h of cell culture. Extensive cell attachment was confirmed by fluorescence and scanning electron microscopy, which showed round monocytes attached at various depths into the fiber networks. Medium concentrations of lactate dehydrogenase (LDH) and tumor necrosis factor alpha (TNF-α) were determined as indicators of viability and inflammatory responses, respectively. Percent LDH concentrations were similar for both 444 fiber networks at all time points, whereas significantly lower than those of 316L control networks at 24 h. All networks elicited low-level secretions of TNF-α, which were significantly lower than that of the positive control wells containing zymosan. Collectively, the results indicate that 444 networks produce comparable responses to medical implant grade 316L networks and are able to support human peripheral blood monocytes in short-term in vitro cultures without inducing significant inflammatory or cytotoxic effects. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013. [ABSTRACT FROM AUTHOR]

Cells residing in living tissues apply forces to their immediate surroundings to promote the restructuration of the extracellular matrix fibres and to transmit mechanical signals to other cells. Here we use a minimalist model to study how these forces, applied locally by cell contraction, propagate through the fibrous network in the extracellular matrix. In particular, we characterize how the transmission of forces is influenced by the connectivity of the network and by the bending rigidity of the fibers. For highly connected fiber networks the stresses spread out isotropically around the cell over a distance that first increases with increasing contraction of the cell and then saturates at a characteristic length. For lower connectivity, however, the stress pattern is highly asymmetric and is characterised by force chains that can transmit stresses over very long distances. We hope that our analysis of force transmission in fibrous networks can provide a new avenue for future studies on how the mechanical feedback between the cell and the ECM is coupled with the microscopic environment around the cells., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Ruiz-Franco and van Der Gucht.)

Abstract: ICTs account nowadays for 2% of total carbon emissions. However, in a time when strict measures to reduce energy consumption in all the industrial and services sectors are required, the ICT sector faces an increase in services and bandwidth demand. The deployment of Next Generation Networks (NGN) will be the answer to this new demand and specifically, the Next Generation Access Networks (NGANs) will provide higher bandwidth access to users. Several policy and cost analysis are being carried out to understand the risks and opportunities of new deployments, though the question of which is the role of energy consumption in NGANs seems off the table. Thus, this paper proposes a model to analyze the energy consumption of the main fiber-based NGAN architectures, i.e. Fiber To The House (FTTH) in both Passive Optical Network (PON) and Point-to-Point (PtP) variations, and FTTx/VDSL. The aim of this analysis is to provide deeper insight on the impact of new deployments on the energy consumption of the ICT sector and the effects of energy consumption on the life-cycle cost of NGANs. The paper presents also an energy consumption comparison of the presented architectures, particularized in the specific geographic and demographic distribution of users of Spain, but easily extendable to other countries. [Copyright &y& Elsevier]

Abstract: The mechanical behavior of an ensemble of fibers which are not bonded to each other subjected to compression is studied using a numerical model. It is shown that the stress-strain curve is a power law and the strain energy is stored predominantly in the bending deformation mode of the fibers. Hysteresis is observed when the system is subjected to cyclic loading-unloading, with a stable hysteresis loop being obtained after few cycles. The deformation is not smooth; rather it is dominated by instabilities which lead to pronounced stress drops. These instabilities are due to relative fiber sliding and rearrangement and a correlation is observed between stress drops and collective sliding events. The resulting jerky flow is observed even in absence of friction between fibers and is a result of the evolution of the system over a rough energy landscape during compression. [Copyright &y& Elsevier]

In this paper we present algorithms for measuring local characteristics of random fiber systems. The calculation of the local directions and radii is based on directional distance transforms and evaluation of the inertia moments and axes of the resulting extremities of the centralized, directed chords. The method provides continuous results while minimizing the runtime by using few sampled directions. Furthermore several steps of improvement for the computation of orientation and radius information are presented. The algorithms are evaluated using synthetic data and applied to images of real microstructures obtained by computer tomography. [ABSTRACT FROM AUTHOR]