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Bulk nacre-like composites with mineral nano-interconnectivity at the same length scale as in the biological material are produced using magnetic alignment and selective sintering techniques. These materials display stiffness and strength levels comparable to that of continuous fiber composites with the advantage of easier processability inherent of discontinuous composites. This opens new possibilities to produce parts with more complex designs.

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Near-infrared (NIR) light-triggered release from polymeric capsules could make a major impact on biological research by enabling remote and spatiotemporal control over the release of encapsulated cargo. The few existing mechanisms for NIR-triggered release have not been widely applied because they require custom synthesis of designer polymers, high-powered lasers to drive inefficient two-photon processes, and/or coencapsulation of bulky inorganic particles. In search of a simpler mechanism, we found that exposure to laser light resonant with the vibrational absorption of water (980 nm) in the NIR region can induce release of payloads encapsulated in particles made from inherently non-photo-responsive polymers. We hypothesize that confined water pockets present in hydrated polymer particles absorb electromagnetic energy and transfer it to the polymer matrix, inducing a thermal phase change. In this study, we show that this simple and highly universal strategy enables instantaneous and controlled release of payloads in aqueous environments as well as in living cells using both pulsed and continuous wavelength lasers without significant heating of the surrounding aqueous solution.

The systematic and controlled reduction of vanadium oxide nanoscrolls results in routes to the largescale preparation of nanostructures of the interesting and useful materials rutile VO 2 and corundum V 2 O 3 . Vanadium oxide (V 2 O 5-δ ) nanoscrolls, prepared by the hydrothermal treatment of aged suspensions of V 2 O 5 and dodecylamine, were reduced in a furnace in an atmosphere of 5% H 2 :95% N 2 under different time and temperature conditions to monitor systematic trends in the structure and morphology of the resulting oxides. The products were characterized by X-ray diffraction (XRD), electron microscopy, N 2 sorption measurements, and electrical transport studies. We find that the reduction conditions (time and temperature) play a significant role in determining the crystal structure and morphology of the products. At short times and low temperatures, the reduction products are rutile VO 2 . These convert to corundum V 2 O 3 when temperatures are increased. In all cases, the appearance of crystalline Bragg peaks in XRD is associated with the breaking up of the starting high-aspect nanostructures into small, dense crystallites. Under certain reduction conditions, porous materials with ill-defined X-ray structures are obtained as intermediates.

Reinforced polymer-based composites are attractive lightweight materials for aircrafts, automobiles, and turbine blades, but still show strength and fracture toughness lower than traditional metals. An interesting approach to address this issue is to fabricate composites with structural features that absorb part of the elastic energy stored in the material during fracture through extrinsic and intrinsic toughening mechanisms behind and ahead of the crack tip, respectively. Inspired by the nacreous layer of mollusk shells, the fracture behavior of multiscale composites that combine intrinsic toughness from a brick-and-mortar structure connected through nanoscale mineral bridges and extrinsic toughness arising from a brittle-ductile laminate architecture at the millimeter scale are fabricated and investigated. Such a hierarchical toughening approach increases the dissipated energy by more than 30-fold during fracture with minimal loss in stiffness and strength. Using simple energy balance arguments and fracture mechanics concepts, guidelines are established for the design of nacre-like composites with a remarkable combination of stiffness, strength, and toughness. This demonstrates the possibility to controllably introduce toughening mechanisms at different length scales and to thus fabricate hierarchical composites with high fracture resistance in spite of the brittle nature of their main inorganic constituents.structures that can bear mechanical loads without damage, whereas high toughness is essential for safety since it ensures a graceful, noncatastrophic failure of the material in case the strength is exceeded. A major challenge arises from the fact that strength and toughness are mutually exclusive in most synthetic materials. [4] This is because both properties are intrinsically related to the ability of chemical bonds to either resist or facilitate stressinduced deformation. [4] Thus, gains in toughness are normally accompanied by a reduction in strength and viceversa. Remarkably, many natural materials are able to overcome this general rule by combining both strength and toughness in hierarchical composite architectures. As a result of a long evolutionary process driven by the need of structural protection or attack, such biological materials achieve outstanding properties using ordinary and abundant building blocks. [5] Replicating, in synthetic composites, the strengthening and toughening strategies that have evolved in these natural systems has been a major research goal in the field of bioinspired materials. [6] Such a research effort requires both understanding the design principles of biological materials and developing processing technologies that allow for their implementation in synthetic composites through bioinspired architectures with exquisite structural control.Studying the structure and mechanical behavior of natural materials at multiple length scales has enabled a better understanding of the design principles underlying the combined strength and toughness of biological composites. [7] Stre...

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