An Alternative Route Towards Metal–Polymer Hybrid Materials Prepared by Vapor‐Phase Processing

Transition metals incorporated into polymers lead to unusual or improved physical properties that significantly differ from those of purely organic polymers. A simple and practicable incorporation of diverse transition metals into any available polymer would make an important contribution to overcome some of the synthetic difficulties of metal‐polymer hybrid materials. Here, it is demonstrated that atomic layer deposition (ALD) can be a promising means to resolve some of those difficulties. It is found that even polytetrafluoroethylene (PTFE) with its great physical and chemical stability can be easily transformed into a transition metal–PTFE hybrid material simply by applying a metal‐oxide ALD process to PTFE. Upon metal incorporation into the PTFE, the molecular structure as well as mechanical properties (tensile behavior) of PTFE were observed to significantly change. For a better understanding of the changes to the material, experimental investigations using Raman spectroscopy, attenuated‐total‐reflection Fourier‐transform infrared spectroscopy, wide‐angle X‐ray diffraction, and energy‐dispersive X‐ray analysis were performed. In addition, with density functional theory calculations, potential bonding states of the incorporated metal into PTFE were modeled and predicted. The ALD‐based vapor‐phase approach for metal incorporation into a polymer could bring about rapid progress in the research area of metal–polymer hybrid materials.     

Application of the Cascade-Correlation network to the classification of circularly scanned images

This paper describes an application of the Cascade-Correlation (CC) network to pattern recognition. The pattern recognition task was to simulate an automatic vision inspection system that had to properly classify five different objects. The feature vectors were extracted from 2D images of circularly scanned images and used as inputs for a neural network that was then trained to classify an unknown presented object. The results show that the CC network is viable tool in pattern recognition tasks. It is able to classify partially occluded objects with high accuracy, and to considerably improve classification of noisy images based on simple histogram trimming preprocessing.     

The Mantis Shrimp Saddle: A Biological Spring Combining Stiffness and Flexibility

Stomatopods are aggressive crustacean predators that use a pair of ultrafast raptorial appendages to strike on prey. This swift movement is driven by a power amplification system comprising components that must be able to repetitively store and release a high amount of elastic energy. An essential component of this system is the saddle structure, in which the elastic energy is stored by bending prior to striking. Here, a comprehensive study that sheds light on the microstructural and chemical designs of the stomatopod's saddle is conducted. MicroCT scans combined with electron microscopy imaging, elemental mapping, high‐resolution confocal Raman microscopy, and nanomechanical mapping show that the saddle is a bilayer structure with sharp changes in chemical composition and mechanical properties between the layers. The outer layer is heavily mineralized whereas the inner layer contains a high content of chitin and proteins, leading to a spatial organization of phases which is optimized for load distribution during saddle bending. The mineralized outer layer sustains compressive stresses, whereas the inner biopolymeric layer provides tensile resistance. These findings reveal that the saddle chemical composition and microstructure have been spatially tuned to generate a stiff, yet flexible structure that is optimized for storage of elastic energy.     

Pseudoelastic behaviour of a natural material is achieved via reversible changes in protein backbone conformation

The egg capsules of marine prosobranch gastropods, commonly know as whelks, function as a protective encapsulant for whelk embryos in wave-swept marine environments. The proteinaceous sheets comprising the wall of whelk egg capsules (WEC) exhibit long-range reversible extensibility with a hysteresis of up to 50 per cent, previously suggested to result from reversible changes in the structure of the constituent protein building blocks. Here, we further investigate the structural changes of the WEC biopolymer at various hierarchical levels using several different time-resolved in situ approaches. We find strong evidence in these biological polymers for a strain-induced reversible transition from an ordered conformational phase to a largely disordered one that leads to the characteristic reversible hysteretic behaviour, which is reminiscent of the pseudoelastic behaviour in some metallic alloys. On the basis of these results, we generate a simple numerical model incorporating a worm-like chain equation to explain the phase transition behaviour of the WEC at the molecular level.