Biological Materials Science: Functional Biological Materials
Sponsored by: TMS Functional Materials Division, TMS Structural Materials Division, TMS: Biomaterials Committee
Program Organizers: Po-Yu Chen, National Tsing Hua University; Francois Barthelat, McGill University; Michael Porter, Clemson University; Steven Naleway, University of Utah

Wednesday 2:00 PM
March 1, 2017
Room: Pacific 15
Location: Marriott Marquis Hotel

Session Chair: Po-Yu Chen, National Tsing Hua University; Michael Porter, Clemson University

2:00 PM  Keynote
Bioinspired Adhesive Surfaces - Designs for Non-Smooth Counter Surfaces: Eduard Arzt1; René Hensel1; 1INM - Leibniz Institute for New Materials; New Materials at Saarland University
    Biological solutions for adhesive functions have inspired many scientific developments worldwide. Artificial dry adhesives based on fibrillar surfaces patterns are now available that mimic the multiple attachment and detachment of gecko toes. While such structures have shown satisfactory performance against flat counter surfaces under ideal conditions, i.e. with ideal relative orientation of two surfaces, such circumstances cannot always be guaranteed. Our new developments are aiming at fibrillar adhesives for surfaces with finite roughness: we have shown that, with judicious design of the surface patterns, also rough surfaces are susceptible to a fibrillar size effect and can exhibit useful gripping performance. In addition, with a new composite design, the interfacial stress distributions and the detachment mechanisms can be controlled, making the adhesive performance less sensitive to surface roughness. These developments, which are complemented by numerical simulations, have the potential of greatly enhancing the applicability of bioinspired adhesive surfaces in non-ideal situations.

2:40 PM  
Exploring the Structural Diversity of Seahorse Tails: Nakul Ravikumar1; Jack Harrison1; Celine Neutens2; Dominique Adriaens2; Michael Porter1; 1Clemson University; 2Ghent University
    Seahorses are in the family of fishes, Syngnathidae, which also includes pipefishes, pipehorses, and seadragons. Seahorse tails are unique in that they exhibit prehensility-the ability to grasp. This ability is prominent in seahorses and some pipehorses, but is absent in the rest. The anatomy of the seahorse tail consists of a square cross-section made up of articulating armored plates. The mechanisms behind the prehensility of their tails, however, is yet to be completely understood. Factors like size, shape, composition, and orientation of the skeletal plates (and muscles) contribute to the overall prehensility. In order to quantify and compare these factors, the tails of ten different species of seahorses are scanned with a micro-computed tomography unit, analyzed using geometric morphometrics and measured by a custom computational software. The results obtained could reveal new strategies for the design of engineering technologies, such as flexible armors or prehensile manipulators.

3:00 PM  
Capturing the Geometry, Microstructure and Mechanical Properties of Marine Diatom Frustules Using Nanoscale Silica Structures: Shi Luo1; Julia Greer1; 1California Institute of Technology
    Diatoms are single-cell algae that form a hard cell wall made of a silica/organic composite. One fascinating aspect of such biosilica shells (frustules) is their intricate and varied architecture. The geometry and design of diatom frustules provide them with extraordinary strength-to-weight ratio. We fabricated silica architectures that fully replicate the diatom geometry using two-photon lithography. These biomimetic structures have a completely amorphous microstructure, and elastic modulus that matches that of the natural diatom biosilica. Three-point bending experiments show these mimetic structures possess comparable strength to natural diatom samples. We also demonstrate fracture properties of natural diatom frustules, and show that the mimetic silica structures have similar fracture toughness and crack-propagation characteristics. The ability to replicate the geometry of diatom frustules down to the nanoscale and capture their mechanical strength can provide a versatile platform for future investigation of such systems.

3:20 PM  
A Functional Natural Adhesive: The Feather Vane and Inspired Designs: Tarah Sullivan1; Marc Meyers1; 1UC San Diego
    Feathers are lightweight, flexible, strong, and spring-like, facilitating a bird’s ability to fly. Flight feathers possess a tiered hierarchical structure consisting of the rachis (main shaft), barbs (beams that branch from the rachis) and barbules (beams that branch from barbs). In this research, feathers of the American white pelican (Pelecanus erythrorhynchos) were characterized by optical microscopy and SEM. The flexural behavior and cohesion of barbules was measured experimentally and analyzed using a simplified mechanical model. Results show that the adherence of barbs to one another via barbules enables a united sail-like material for the capture of air. A model for this adhesion mechanism is proposed. The unique structure of the feather could allow for the design and synthesis of new bio-inspired materials and devices. This research is funded by AFOSR MURI (AFOSR-FA9550-15-1-0009).

3:40 PM Break

4:00 PM  Invited
Smart Biocoatings for Tunable Bioactivity at the Bio-Material Site: Candan Tamerler1; 1University of Kansas
    Despite the improvements in implant technology, most implant failures can be attributed to either infection or loosening resulting from poor integration with host tissue. In early stages following surgery, implant surface is most vulnerable to bacterial colonization and bacterial pathogens are also most susceptible to antimicrobial treatment. Immediate prevention of bacterial attachment on the implant surface is therefore critical in prevention of infection related failure. However, host cell attachment and viability at the interface is also critical to host bone integration to prevent implant loosening. Our biomimetic approach incorporates to design engineered biocoatings to prevent bacterial colonization on a variety of bio-material site while not negatively affecting host response rather allowing to tailor desired bioactivity at the site to improve integration of implant material with the host. These engineered biocoatings are chimerically designed to both self-anchor and bring antimicrobial as well as cell signaling to mineralization activities to the site.

4:30 PM  
Biological Martensitic Phase Transformations in Bacterial Flagella and other Helical Protein Crystals: Ricardo Komai1; Greg Olson1; 1Northwestern University
    Bacterial flagella are cylindrically crystalline helices of proteins capable of conformational changes responsible for bacterial motion. These proteins respond to temperature and chemical changes in local environment as well as mechanical changes in applied torque to the flagella, which induce biologically martensitic phase transformations. By altering torque direction, the bacteria can rapidly transform from a swimming mode to a tumbling mode that randomly reorients the bacterial motion. Previously, phase diagrams have been developed for the phase transitions of these flagella by chemically changing pH and salt concentration. Limited information regarding the influence of mechanical forces upon these transitions prohibit complete understanding of bacterial motion. Recent work translating martensitic transformations to cylindrically crystalline proteins has enabled the development of stress-temperature phase diagrams. This work explains the thermodynamics of these phase transformations and indicates further parallels that can be drawn to other helical proteins by applying what is known regarding martensitic transformations.

4:50 PM  
Mechanical Property and Humidity-triggered Reaction of the Cones of Liquidambar Formosana: Hsin-Juei Wang1; Cheng-Che Tung1; Chun-Lin Lin1; Po-Yu Chen1; 1National Tsing Hua University
    Liquidambar Formosana is a member of the maple family, featured by its maple-like leaves and spiny cones. In this study, we focus on the mechanical property and humidity-triggered reaction of its cone. The cone is composed of three parts: the spiny outer shell, the beak-like corks that serve as seed carriers and the buckyball-like structure which supports the whole structure. Microstructure features of the cone are characterized by micro-CT and SEM and the mechanical properties were measured by compression tests. The cone consists of well-organized open cell foams which provide high specific strength and prevent buckling under compression. Additionally, the humidity-triggered shape change is investigated. The corks open when cone is dried and close when the humidity increases, which facile the conservation and spreading of seeds. These unique characteristics show great potential in the designs of novel light-weight, anti-buckling composites, and drug delivery devices and bio-inspired architectures.

5:10 PM  
Empirically Testing Vaterite Structural Models Using Neutron Diffraction and Thermal Analysis: Bryan Chakoumakos1; Brenda Pracheil1; Ryan Koenigs2; Ronald Bruch2; Mikhail Feygenson3; 1Oak Ridge National Lab; 2Wisconsin Department of Natural Resources; 3Forschungszentrum Jülich
    Otoliths, CaCO3 ear bones, are commonly used age and growth structures of fishes, and most are comprised of the densest CaCO3 polymorph, aragonite. Sturgeon otoliths, in contrast, are purportedly the rare and structurally enigmatic polymorph, vaterite. Vaterite is an important material used in biomedical to personal care applications. While sturgeon otoliths are primarily composed of vaterite, they also contain calcite. For the vaterite fraction, neutron diffraction data provide enhanced discrimination of the carbonate group compared to x-ray diffraction data, owing to the different relative neutron scattering lengths, and offer the opportunity to uniquely test the various crystal structural models proposed for vaterite. Of those, space group P6522 model best fits the neutron diffraction data, and allows structure refinement using rigid carbonate groups. Research was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U. S. Department of Energy.