Search for: All records

Freeze casting under external fields (magnetic, electric, or acoustic) produces porous materials having local, regional, and global microstructural order in specific directions. In freeze casting, porosity is typically formed by the directional solidification of a liquid colloidal suspension. Adding external fields to the process allows for structured nucleation of ice and manipulation of particles during solidification. External control over the distribution of particles is governed by a competition of forces between constitutional supercooling and electromagnetism or acoustic radiation. Here, we review studies that apply external fields to create porous ceramics with different microstructural patterns, gradients, and anisotropic alignments. The resulting materials possess distinct gradient, core–shell, ring, helical, or long-range alignment and enhanced anisotropic mechanical properties. 

Keratin is one of the most common structural biopolymers exhibiting high strength, toughness, and low density. It is found in various tissues such as hairs, feathers, horns, and hooves with various functionalities. For instance, horn keratin absorbs a large amount of energy during intraspecific fights. Keratinized tissues are permanent tissues because of their basic composition consisting of dead keratinized cells that are not able to remodel or regrow once broken or damaged. The lack of a self‐healing mechanism presents a problem for horns, as they are under continued high risk from mechanical damage. In the present work, it is shown for the first time that a combination of material architecture and a water‐assisted recovery mechanism, in the horn of bighorn sheep, endows them with shape and mechanical property recoverability after being subjected to severe compressive loading. Moreover, the effect of hydration is unraveled, on the material molecular structure and mechanical behavior, by means of synchrotron wide angle X‐ray diffraction, Fourier transform infrared spectroscopy, nanoindentation, and in situ and ex situ tensile tests. The recovery and remodeling mechanism is anisotropic and quite distinct to the self‐healing of living tissue such as bones.

 

The brain is one of the most important and complicated organs, but it is delicate and therefore needs to be protected from external forces. This makes the pecking behavior of the Woodpecker so impressive, as they are not known to sustain any brain injury due to their anatomical adaptations (a specialized beak, skull bone, and hyoid bone). However, the relationship between the morphology of the woodpecker head and its mechanical function against damage from daily pecking habits remains an open question. Aided by recent technical advancements, these questions can be explored by applying new materials science concepts of bioinspiration and bioexploration to identify adapted structures/materials in a design that results from millions of years of evolution. Two main features, including the beam‐like bar structure of the jugal bone acting as a main stress deflector and the high natural frequency of the skull bone of woodpeckers can teach two lessons for potential materials development as well as engineering applications: protection of a delicate internal organ occurs by redirection of the main stress pathway and a large mismatch of the natural frequencies between the skull and brain avoids resonance and reduces the overall load experienced by the brain.