Showing papers by "Chiara Daraio published in 2022"
TL;DR: Liu et al. as mentioned in this paper proposed a growth-inspired program for generating irregular materials from a limited number of basic elements, which echoed the diversity of natural systems with a large range of functional properties.
Abstract: Biomaterials display microstructures that are geometrically irregular and functionally efficient. Understanding the role of irregularity in determining material properties offers a new path to engineer materials with superior functionalities, such as imperfection insensitivity, enhanced impact absorption, and stress redirection. We uncover fundamental, probabilistic structure–property relationships using a growth-inspired program that evokes the formation of stochastic architectures in natural systems. This virtual growth program imposes a set of local rules on a limited number of basic elements. It generates materials that exhibit a large variation in functional properties starting from very limited initial resources, which echoes the diversity of biological systems. We identify basic rules to control mechanical properties by independently varying the microstructure’s topology and geometry in a general, graph-based representation of irregular materials. Description An irregular plan Materials with irregular microstructures are common in the natural world and often have interesting properties. Liu et al. devised a growth-inspired program for generating irregular materials from a limited number of basic elements. Using building blocks with arbitrary complexity, the authors stochastically connected them subject to a set of local rules. The results echoed the diversity of natural systems with a large range of functional properties. —BG A strategy for developing irregular materials can lead to a wide range of functional properties.
16 citations
TL;DR: In this paper , a three-dimensional metamaterial with the ability to attenuate both airborne sound and mechanical vibrations, simultaneously, and in all directions, was studied, and a combination of analytical, numerical, and experimental methods was used to study the metammaterial.
Abstract: Through a combination of analytical, numerical, and experimental methods, we study a three-dimensional metamaterial with the ability to attenuate both airborne sound and mechanical vibrations, simultaneously, and in all directions. In addition, due to the auxetic nature of the design (i.e., having a negative Poisson's ratio), the metamaterial can shrink (or expand) in a relatively uniform manner, without buckling. We utilize an external load to cause a systematic shape change in the metamaterial and tune the attenuation frequency bands. The presented design principles can be utilized in many applications related to acoustic and elastic wave manipulation as well as acoustic devices.
6 citations
TL;DR: In this article , the authors proposed a non-self-similar hierarchical geometries for elastic metamaterials to create periodic structures supporting multiple, highly attenuative and broadband bandgaps involving different scattering mechanisms, namely, Bragg scattering, local resonance and/or inertial amplification, at different frequencies.
5 citations
TL;DR: In this paper , a method to obtain self-bonded biocomposite materials from cultured plant cells is presented, subjecting cells to a cold-compression molding process creates hierarchical bi-ocomposites that have stiffness and strength comparable to commodity plastics, while being 100% biodegradable in soil.
Abstract: Significance The development of novel degradable biocomposites can contribute to answering the increasing global demand for sustainable materials. We present a method to obtain self-bonded biocomposite materials from cultured plant cells. Subjecting cells to a cold-compression molding process creates hierarchical biocomposites that have stiffness and strength comparable to commodity plastics, while being 100% biodegradable in soil. Introducing fillers expands the attainable functionalities, demonstrating the versatility of the proposed platform. The use of fast-growing plant cells offers the benefits of short harvest time, zero biomass waste during processing, in situ manufacturing, and no arable land requirement. The approach allows the possibility of further tuning the final material properties by genetically engineering the processed cells.
3 citations
TL;DR: This work studies the contributions of the CW, microtubules (MTs) and actin filaments (AFs), in the mechanical properties of Nicotiana tabacum cells to confirm the dominant role of turgor pressure.
Abstract: Abstract Studies on the mechanics of plant cells usually focus on understanding the effects of turgor pressure and properties of the cell wall (CW). While the functional roles of the underlying cytoskeleton have been studied, the extent to which it contributes to the mechanical properties of cells is not elucidated. Here, we study the contributions of the CW, microtubules (MTs) and actin filaments (AFs), in the mechanical properties of Nicotiana tabacum cells. We use a multiscale biomechanical assay comprised of atomic force microscopy and micro-indentation in solutions that (i) remove MTs and AFs and (ii) alter osmotic pressures in the cells. To compare measurements obtained by the two mechanical tests, we develop two generative statistical models to describe the cell’s behaviour using one or both datasets. Our results illustrate that MTs and AFs contribute significantly to cell stiffness and dissipated energy, while confirming the dominant role of turgor pressure.
TL;DR: In this paper , the response of a one-dimensional phononic lattice with time-periodic elastic properties is studied with experimental, numerical and theoretical approaches in both linear and nonlinear regimes.
Abstract: The propagation of acoustic and elastic waves in time-varying, spatially homogeneous media can exhibit different phenomena when compared to traditional spatially varying, temporally homogeneous media. In the present work, the response of a one-dimensional phononic lattice with time-periodic elastic properties is studied with experimental, numerical and theoretical approaches in both linear and nonlinear regimes. The system consists of repelling magnetic masses with grounding stiffness controlled by electrical coils driven with electrical signals that vary periodically in time. For small-amplitude excitation, in agreement with linear theoretical predictions, wave-number band gaps emerge. The underlying instabilities associated to the wave-number band gaps are investigated with Floquet theory and the resulting parametric amplification is observed in both theory and experiments. In contrast to genuinely linear systems, large-amplitude responses are stabilized via the nonlinear nature of the magnetic interactions of the system, and results in a family of nonlinear time-periodic states. The bifurcation structure of the periodic states is studied. It is found the linear theory correctly predicts parameter values from which the time-periodic states bifurcate from the zero state. In the presence of an external drive, the parametric amplification induced by the wave-number band gap can lead to bounded and stable responses that are temporally quasiperiodic. Controlling the propagation of acoustic and elastic waves by balancing nonlinearity and external modulation offers a new dimension in the realization of advanced signal processing and telecommunication devices. For example, it could enable time-varying, cross-frequency operation, mode- and frequency-conversion, and signal-to-noise ratio enhancements.
TL;DR: In this article , the authors proposed the displacement amplification method for capacitive temperature sensors, where two high coefficient of thermal expansion (CTE) metallic layers are separated by a low-CTE dielectric layer, and then they are glued together at a few locations.
Abstract: We propose the realization of capacitive temperature sensors based on the concept of displacement amplification. Our design features two high coefficient of thermal expansion (CTE) metallic layers separated by a low-CTE dielectric layer; conductive and dielectric layers are then separated by a thin air gap and glued together at a few locations. As the temperature increases, the high-CTE layer tends to expand more than the low-CTE one. Owing to the constraint to planar expansion imposed by the low-CTE layer, this results in large out-of-plane displacements of the high-CTE layer – hence the displacement amplification term. In our case, the high-CTE layer buckles and causes a reduction of the gap between conductive and dielectric layers; in turn, this results in a large change of capacitance. First, we illustrate the concept via numerical simulations. Then, we realize a low-cost prototype of such sensor by using aluminum foil as conductor, paper as dielectric, and by gluing the layers together with cyanoacrylate. Our results demonstrate the potential of this simple design as a route towards efficient and low-cost temperature sensors.
TL;DR: In this paper , the authors study helical acoustic metamaterials and demonstrate the ability to vary the materials' dispersion properties by perturbing the moment of inertia of the system and introducing centro-asymmetry.
Abstract: We study helical acoustic metamaterials and demonstrate the ability to vary the materials' dispersion properties by controlling geometrical structure and mass distribution. By locally adding eccentric, higher density elements in the unit cells, we perturb the moment of inertia of the system and introduce centro-asymmetry. This allows controlling the degree of mode coupling and the width of subwavelength bandgaps in the dispersion relation, which are the product of enhanced local resonance hybridization. We characterize the distinct normal modes in our metamaterials using finite element simulations and analytically quantify the coupling between each mode. The evolution of acoustic bandgaps induced by the increasing level of centro-asymmetry is experimentally validated with 3D-printed structures.