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1. Shape-morphing living composites

   https://doi.org/10.1126/sciadv.aax8582  

   Rivera-Tarazona, L. K.; Bhat, V. D.; Kim, H.; Campbell, Z. T.; Ware, T. H. (January 2020, Science Advances)

   This work establishes a means to exploit genetic networks to create living synthetic composites that change shape in response to specific biochemical or physical stimuli. Baker’s yeast embedded in a hydrogel forms a responsive material where cellular proliferation leads to a controllable increase in the composite volume of up to 400%. Genetic manipulation of the yeast enables composites where volume change on exposure to l -histidine is 14× higher than volume change when exposed to d -histidine or other amino acids. By encoding an optogenetic switch into the yeast, spatiotemporally controlled shape change is induced with pulses of dim blue light (2.7 mW/cm 2 ). These living, shape-changing materials may enable sensors or medical devices that respond to highly specific cues found within a biological milieu. 

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2. Review of Morphing Laminated Composites

   https://doi.org/10.1115/1.4044269  

   Chillara, V. S.; Dapino, M. J. (January 2020, Applied Mechanics Reviews)

   Abstract Morphing structures, defined as body panels that are capable of a drastic autonomous shape transformation, have gained importance in the aerospace, automotive, and soft robotics industries since they address the need to switch between shapes for optimal performance over the range of operation. Laminated composites are attractive for morphing because multiple laminae, each serving a specific function, can be combined to address multiple functional requirements such as shape transformation, structural integrity, safety, aerodynamic performance, and minimal actuation energy. This paper presents a review of laminated composite designs for morphing structures. The trends in morphing composites research are outlined and the literature on laminated composites is categorized based on deformation modes and multifunctional approaches. Materials commonly used in morphing structures are classified based on their properties. Composite designs for various morphing modes such as stretching, flexure, and folding are summarized and their performance is compared. Based on the literature, the laminae in an n-layered composite are classified based on function into three types: constraining, adaptive, and prestressed. A general analytical modeling framework is presented for composites comprising the three types of functional laminae. Modeling developments for each morphing mode and for actuation using smart material-based active layers are discussed. Results, presented for each deformation mode, indicate that the analytical modeling can not only provide insight into the structure's mechanics but also serve as a guide for geometric design and material selection. 

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3. Quasiperiodic Composites: Multiscale Reiterated Homogenization

   https://doi.org/10.1109/MetaMaterials.2019.8900926  

   Cherkaev, E.; Guenneau, S.; Hutridurga, H.; Wellander, N. (September 2019, 2019 Thirteenth International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials))

   With recent technological advances, quasiperiodic and aperiodic materials present a novel class of metamaterials that possess very unusual, extraordinary properties such as superconductivity, unusual mechanical properties and diffraction patterns, extremely low thermal conductivity, etc. As all these properties critically depend on the microgeometry of the media, the methods that allow characterizing the effective properties of such materials are of paramount importance. In this paper, we analyze the effective properties of a class of multiscale composites consisting of periodic and quasiperiodic phases appearing at different scales. We derive homogenized equations for the effective behavior of the composite and discover a variety of new effects which could have interesting applications in the control of wave and diffusion phenomena. 

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4. 3D printed elastomer ternary composites

   https://doi.org/10.1049/ell2.12749  

   Korivi, Naga; Mahbub, Rifat; Ahmadi, Zahra; Azadehranjbar, Soodabeh; Shield, Jeffrey E; Ni, Yuanyuan; Yuan, Yifan; Xu, Xiaoshan; Gong, Limin; Jeelani, Shaik; et al (April 2023, Electronics Letters)

   This paper describes the 3D printing of a ternary composite of polydimethylsiloxane (PDMS) and nanoparticles of iron oxide and barium titanate. The composite was printed using a commercially available 3D printer. Thermal curing of the composite during printing allowed for overall low process times of a few minutes. Scanning electron microscopy indicated uniform composite layers. The resulting composite films showed ferromagnetic behaviour, and applicability in magnetic actuation and piezoelectric energy harvesting. 

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5. Tough, aorta-inspired soft composites

   https://doi.org/10.1073/pnas.2123497119  

   Mo, Chengyang; Long, Haiyi; Raney, Jordan R. (July 2022, Proceedings of the National Academy of Sciences)

   Spatial variations in fiber alignment (and, therefore, in mechanical anisotropy) play a central role in the excellent toughness and fatigue characteristics of many biological materials. In this work, we examine the effect of fiber alignment in soft composites, including both “in-plane” and “out-of-plane” fiber arrangements. We take inspiration from the spatial variations of fiber alignment found in the aorta to three-dimensionally (3D) print soft, tough silicone composites with an excellent combination of stiffness, toughness, and fatigue threshold, regardless of the direction of loading. These aorta-inspired composites exhibit mechanical properties comparable to skin, with excellent combinations of stiffness and toughness not previously observed in synthetic soft materials. 

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