Spider silk is a tough, elastic and lightweight biomaterial, although there is a lack of tools available for non-invasive processing of silk structures. Here we show that nonlinear multiphoton interactions of silk with few-cycle femtosecond pulses allow the processing and heterostructuring of the material in ambient air. Two qualitatively different responses, bulging by multiphoton absorption and plasma-assisted ablation, are observed for low- and high-peak intensities, respectively. Plasma ablation allows us to make localized nanocuts, microrods, nanotips and periodic patterns with minimal damage while preserving molecular structure. The bulging regime facilitates confined bending and microwelding of silk with materials such as metal, glass and Kevlar with strengths comparable to pristine silk. Moreover, analysis of Raman bands of microwelded joints reveals that the polypeptide backbone remains intact while perturbing its weak hydrogen bonds. Using this approach, we fabricate silk-based functional topological microstructures, such as Mobiüs strips, chiral helices and silk-based sensors.

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The bamboo leaf ash (BLA) which was extruded from agro waste was used as a particulate reinforcement to produce economical AMMCs. The dry sliding wear behavior of Al-4.5 wt.% Cu alloy with the addition of 2, 4 and 6 wt.% of BLA by stir casting method was analyzed using pin-on-disc wear test apparatus. The typical L27 orthogonal array was selected to perform the experimental work. The effect of the testing parameters on wear rate, SWR and COF of the fabricated aluminium composites were studied using Grey relational analysis with Taguchi method. The ANOVA analysis was employed to identify the significance of testing parameters and statistical analysis was performed. The testing parameters play a crucial role to control the dry sliding wear behavior of the fabricated aluminium composites. The confirmation test has been performed to validate the predictive statistical value with the experimental value. The wear mechanism was analyzed using scanning electron microscope with Energy Dispersive Analysis of X-ray, it was observed that the grooves size decreased with the addition of BLA particles in the composite in comparison with matrix alloy resulting in decreased wear rate with increase in BLA content. The significant amount of mechanical mixed layer formation was observed to increase in wear resistance of the composites.

We demonstrate that spider draglines exhibit a fatigueless response in extreme cyclic torsion up to its breaking limit. The well defined Raman bands at 1095 and 1245 cm -1 shifted linearly towards lower wavenumbers versus increasing twist in both clockwise and counter-clockwise directions. Under thousands of continuous loading cycles of twist strain approaching its breaking limit, all the Raman bands were preserved and the characteristic Raman peak shifts were found to be reversible. Besides, nanoscale surface profile of the worked silk appeared as good as the pristine silk. This unique fatigueless twist response of draglines, facilitated by reversible deformation of protein molecules, could find applications in durable miniatured devices. V C 2014 AIP Publishing LLC.

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