Abstract
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.
| Original language | English (US) |
|---|---|
| Article number | 1901077 |
| Journal | Advanced Functional Materials |
| Volume | 29 |
| Issue number | 27 |
| DOIs | |
| State | Published - Jul 4 2019 |
Funding
The authors gratefully acknowledge financial support from a Multi-University Research Initiative through the Air Force Office of Scientific Research (Grant No. AFOSR-FA9550-15-1-0009) and a NSF Biomaterials Grant 1507978. The authors also acknowledge the use of beamline 7.3.3 at the Advanced Light Source at the Lawrence Berkeley National Laboratory, which is supported by the Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering of the US Department of Energy under Contract no. DE-AC02-05CH11231. The authors thank Mason Mackey at National Center for Microscopy and Imaging Research (NCMIR), Timo Meerloo and Ying Jones at Electron Microscopy Facility at UC San Diego for providing help with ultramicrotome. Additionally, the authors thank Ryan Anderson of the Nano3 Laboratory of CalIt2 for helping with the optical microscopy. This work was performed in part at the San Diego Nanotechnology Infrastructure (SDNI) of UCSD, a member of the National Nanotechnology Coordinated Infrastructure, which is supported by the National Science Foundation (Grant ECCS-1542148).
Keywords
- energy absorption
- keratin
- mechanical behavior
- self-recovery
- water effects
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- General Chemistry
- Condensed Matter Physics
- General Materials Science
- Electrochemistry
- Biomaterials