The tendon-to-bone attachment (enthesis) is a complex hierarchical tissue that connects stiff bone to compliant tendon. The attachment site at the micrometer scale exhibits gradients in mineral content and collagen orientation, which likely act to minimize stress concentrations. The physiological micromechanics of the attachment thus define resultant performance, but difficulties in sample preparation and mechanical testing at this scale have restricted understanding of structure-mechanical function. Here, microscale beams from entheses of wild type mice and mice with mineral defects were prepared using cryo-focused ion beam milling and pulled to failure using a modified atomic force microscopy system. Micromechanical behavior of tendon-to-bone structures, including elastic modulus, strength, resilience, and toughness, were obtained. Results demonstrated considerably higher mechanical performance at the micrometer length scale compared to the millimeter tissue length scale, describing enthesis material properties without the influence of higher order structural effects such as defects. Micromechanical investigation revealed a decrease in strength in entheses with mineral defects. To further examine structure-mechanical function relationships, local deformation behavior along the tendon-to-bone attachment was determined using local image correlation. A high compliance zone near the mineralized gradient of the attachment was clearly identified and highlighted the lack of correlation between mineral distribution and strain on the low-mineral end of the attachment. This compliant region is proposed to act as an energy absorbing component, limiting catastrophic failure within the tendon-to-bone attachment through higher local deformation. This understanding of tendon-to-bone micromechanics demonstrates the critical role of micrometer scale features in the mechanics of the tissue.

Hierarchical flower-like SnO2 nanospheres have been prepared by one step hydrothermal reaction with surfactant-free. A possible growth mechanism is proposed. The application of this nanostructure in gas sensor for detecting ethanol reveals that the as-prepared SnO2 nanospheres exhibit a high sensitivity and short response/recovery time. The flower-like SnO2 nanostructures were also used as anode materials for Li-ion battery, whose cyclic voltammetry, charge–discharge galvanstatic behavior and cycle performance were examined. For the sample with 6 h hydrothermal time, a highly stable capacity about 570 mA g–1 after 100 cycles is achieved. The gas sensing properties are mainly determined by the specific surface area, and the 3D nanostructured films composed of flower-like SnO2 nanospheres are favorable for the diffusion of gas molecules. At the same time, the high specific surface area of the flower-like SnO2 nanospheres can provide more electrochemical active sites for Li storage, and the 3D nanostructured films composed of this nanostructure facilitate the diffusion of electrolyte. Furthermore, the short rods on the nanospheres may provide a buffer to alleviate volume change during the alloying and dealloying reactions between Sn and Li. The superior properties achieved here suggest that the as-prepared hierarchical flower-like SnO2 nanostructures have potential application in Li-ion battery and gas sensor.

Advances in stretchable electronics concern engineering of materials with strain-accommodating architectures and fabrication of nanocomposites by embedding a conductive component into an elastomer. The development of organic conductors that can intrinsically stretch and repair themselves after mechanical damage is only in the early stages yet opens unprecedented opportunities for stretchable electronics. Such functional materials would allow extended lifetimes of electronics as well as simpler processing methods for fabricating stretchable electronics. Herein, we present a unique molecular approach to intrinsically stretchable and healable conjugated polymers. The simple yet versatile synthetic procedure enables one to fine-tune the electrical and mechanical properties without disrupting the electronic properties of the conjugated polymer. The designed material is comprised of a hydrogen-bonding graft copolymer with a conjugated backbone. The morphological changes, which are affected by the composition of functional side chains, and the solvent quality of the casting solution play a crucial role in the synthesis of highly stretchable and room-temperature healable conductive electronic materials.

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