Stretchable electronics, which can retain their functions under stretching, have attracted great interest in recent decades. Elastic substrates, which bear the applied strain and regulate the strain ...distribution in circuits, are indispensable components in stretchable electronics. Moreover, the self‐healing property of the substrate is a premise to endow stretchable electronics with the same characteristics, so the device may recover from failure resulting from large and frequent deformations. Therefore, the properties of the elastic substrate are crucial to the overall performance of stretchable devices. Poly(dimethylsiloxane) (PDMS) is widely used as the substrate material for stretchable electronics, not only because of its advantages, which include stable chemical properties, good thermal stability, transparency, and biological compatibility, but also because of its capability of attaining designer functionalities via surface modification and bulk property tailoring. Herein, the strategies for fabricating stretchable electronics on PDMS substrates are summarized, and the influence of the physical and chemical properties of PDMS, including surface chemical status, physical modulus, geometric structures, and self‐healing properties, on the performance of stretchable electronics is discussed. Finally, the challenges and future opportunities of stretchable electronics based on PDMS substrates are considered.
Elastic substrates, especially poly(dimethylsiloxane) (PDMS) substrates, are indispensable components for emerging stretchable electronics. Detailed design concepts and fabrication strategies for structured, patterned, and self‐healing PDMS substrates, and their contributions in enhancing the mechanical performance of stretchable electronics are discussed. Future perspectives and challenges in the development of stretchable and self‐healing PDMS substrates are highlighted.
Soft material for soft actuators Miriyev, Aslan; Stack, Kenneth; Lipson, Hod
Nature communications,
09/2017, Letnik:
8, Številka:
1
Journal Article
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Inspired by natural muscle, a key challenge in soft robotics is to develop self-contained electrically driven soft actuators with high strain density. Various characteristics of existing ...technologies, such as the high voltages required to trigger electroactive polymers ( > 1KV), low strain ( < 10%) of shape memory alloys and the need for external compressors and pressure-regulating components for hydraulic or pneumatic fluidicelastomer actuators, limit their practicality for untethered applications. Here we show a single self-contained soft robust composite material that combines the elastic properties of a polymeric matrix and the extreme volume change accompanying liquid-vapor transition. The material combines a high strain (up to 900%) and correspondingly high stress (up to 1.3 MPa) with low density (0.84 g cm
). Along with its extremely low cost (about 3 cent per gram), simplicity of fabrication and environment-friendliness, these properties could enable new kinds of electrically driven entirely soft robots.The development of self-contained electrically driven soft actuators with high strain density is difficult. Here the authors show a single self-contained soft robust composite material that combines the elastic properties of a polymeric matrix and the extreme volume change accompanying liquid vapour transition.
A detailed study has been undertaken of the mechanisms of stress transfer in polymeric matrices with different values of Young's modulus, Em, reinforced by graphene nanoplatelets (GNPs). For each ...material, the Young's modulus of the graphene filler, Ef, has been determined using the rule of mixtures and it is found to scale with the value of Em. Additionally stress-induced Raman bands shifts for the different polymer matrices show different levels of stress transfer from the polymer matrix to the GNPs, which again scale with Em. A theory has been developed to predict the stiffness of the bulk nanocomposites from the mechanics of stress transfer from the matrix to the GNP reinforcement based upon the shear-lag deformation of individual graphene nanoplatelets. Overall it is found that it is only possible to realise the theoretical Young's modulus of graphene of 1.05 TPa for discontinuous nanoplatelets as Em approaches 1 TPa; the effective modulus of the reinforcement will always be less for lower values of Em. For flexible polymeric matrices the level of reinforcement is independent of the graphene Young's modulus and, in general, the best reinforcement will be obtained in nanocomposites with strong graphene-polymer interfaces and aligned nanoplatelets with high aspect ratios.
Materials made from active, living, or robotic components can display emergent properties arising from local sensing and computation. Here, we realize a freestanding active metabeam with ...piezoelectric elements and electronic feed-forward control that gives rise to an odd micropolar elasticity absent in energy-conserving media. The non-reciprocal odd modulus enables bending and shearing cycles that convert electrical energy into mechanical work, and vice versa. The sign of this elastic modulus is linked to a non-Hermitian topological index that determines the localization of vibrational modes to sample boundaries. At finite frequency, we can also tune the phase angle of the active modulus to produce a direction-dependent bending modulus and control non-Hermitian vibrational properties. Our continuum approach, built on symmetries and conservation laws, could be exploited to design others systems such as synthetic biofilaments and membranes with feed-forward control loops.
Microfluidics
In article 2200246, Annette M. Schmidt's and her co‐workers' approach toward spherical, mm‐scaled PAAm hydrogel beads with adjustable, soft elastic properties as a matrix for scalable ...cell culture is described. The beads are produced by a continuous microfluidic approach, and after surface modification with biomarkers, their suitability as a matrix for scalable cell cultivation is successfully demonstrated with three different cell types in model experiments and in a tidal bioreactor system.
The morphological and physical properties of interfaces can significantly affect the overall mechanical properties of nano- and micro-particle reinforced composites. In this work, we devise a general ...micromechanical framework to predict the effective elastic moduli of particle-reinforced composites containing ellipsoidal nano- or micro-particles with varying interface properties (e.g., both hard and soft). Specifically, the interface is treated as an interphase perfectly bonding the particle and matrix with a finite thickness and volume fraction. The morphological characteristics of the interface (e.g., volume fraction) are quantified using a statistical geometry approach and subsequently incorporated into the Mori-Tanaka average scheme with Eshelby's equivalent inclusion theory to derive the general micromechanical framework for the three-phase composites with non-spherical inclusions. We show that our new framework leads to predictions of the elastic moduli of a wide spectrum of nano- and micro-particle reinforced composites with both soft and hard interfaces to a reasonable accuracy by comparing with available experimental data and predictions from other theoretical frameworks. The general framework provides a robust and convenient predictive toolkit for composite design and evaluation.
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•A general model for elastic moduli of nano-/micro-particle composites (N/MPCs).•N/MPCs contain nonspherical particles with varying hard/soft interface properties.•The general micromechanical framework (GMF) has a reasonable accuracy.•GMF incorporates hard and soft interfaces into the elastic properties of N/MPCs.•The derived results provide a robust predictive toolkit for the design of N/MPCs.
•Heavy metal ions doped borate glasses are synthesized in laboratory.•Structural and Elastic properties are calculated for the prepared glasses.•Formation of bridging oxygen composes the glass to be ...a tightly packed structure.•The best shielding performance was observed with the BPBBaD glass.
The effect of modifier ions in different basis have been analyzed through a new series of heavy metals incorporated borate based glasses 39H3BO3+30PbO+20MO+10Bi2O3 +1Dy2O3 (where M=Ca,Sr,Ba,Na and K) which are synthesized following melt quenching technique for radiation screening applications. The potentiality of glasses to withstand the penetration of fast moving neutrons is checked by various studies. Functional groups are identified through different stretching and bending modes of vibrations within the glass membrane through FTIR spectral analysis. In addition to that, other structural properties like Boron-Boron distance (dB−B), molar volume of oxygen (Vo), Oxygen Packing Density (OPD), optical basicity (Λth) and Bond density (nb) are calculated theoretically. The bonding nature (β) and nephelauxetic ratio (δ) values reveals that the glasses possess more of ionic linkages. The high density value exhibited by the Bismuth lead borate glasses indicates their capability to act as a good shielding material in reactors emitting hazardous radiation. Different moduli of elasticity (E, K, G, σ) values for the present glasses are calculated and the results reveal the enhancement in shielding performances when compared to other existing glasses and a comparative study is made on it. Optical studies are carried out and the absorption of Dy3+ions to different energy levels is observed and optical band gap (Eopt) values of the synthesized glasses are calculated along with the Urbach energy (ΔE) values. Radiation shielding properties of the produced glasses were investigated in terms of the mass attenuation coefficients (µm), transmission fraction (T), half value layer (HVL) and effective atomic number (Zeff) parameters. The results attained in the shielding study indicated that glass specimen with M = Ba exhibits enhanced shielding behavior as Ba owns high atomic number (Z) compared to other elements. Glass specimen with M = Na shows the poorest shielding characteristics due to the low Z of Na.
An analysis of the symmetries characterizing the micro-architecture topologies and the elastic material properties is performed. The goal is to elucidate a systematic procedure that facilitates the ...design of elastic metamaterial with a prescribed target elasticity tensor via inverse homogenization methodologies. This systematic procedure, which is defined through a set of rules, is based on the relationship established between the elasticity tensor symmetries and the symmetry displayed by the micro-architecture topology.
Following this procedure, it can be guaranteed that the designed composites, with the attained micro-structures, have effective elasticity tensors that possess the same or higher symmetries than those shown by the target elasticity tensors. Furthermore, the micro-architectures designed through this technique display simple topologies.
Both properties that are supplied by the procedure, i.e., the accomplishment of the required symmetry of the composite homogenized elasticity tensor combined with the topology simplicity, are assessed through numerical simulations of several micro-architecture design problems. They are designed by formulating the inverse homogenization problem as a topology optimization problem which is solved with two different standard algorithms. The proposed procedure and the conclusions here obtained do not depend on the algorithm adopted for solving this problem.
Theoretical and experimental methods for obtaining and investigating effective thermomechanical characteristics - residual stresses and deformation in panels made of nanomodified materials with ...asymmetrical reinforcement scheme have been developed in this paper. The study of the residual stress-strain state of structural elements made of carbon plastic using the values of thermoelastic characteristics of composite monolayers identified on the basis of the developed methods meade it possible to reveal the possibility of reducing the residual stress-strain state in structures with asymmetric reinforcement schemes.
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