Two high school interns, Kadija Amba and Gloria Chukwueke, from the Preuss High School and Buay Deng, a UCSD undergraduate volunteer, worked on the biological materials project with graduate students, Po-Yu Chen and Albert Lin.

Kadija, Po-Yu, Gloria, and Albert (from left to right) working in the aquarium at Scripps Institution of Oceanography, where we raise abalone and crab.

Abalone Shell and Crab ExoskeletonAbalone Shell and Crab Exoskeleton

SEM micrograph showing mineral bridges (marked by arrows) between aragonite tiles.

The abalone shell is composed of CaCO3 (aragonite) tiles

and protein layers between them. The resulting structure yields unique mechanical properties. We study the growth, structure, and mechanical properties of abalone shells and discovered that the mineral bridges (~50 nm in diameter) play a key role in enhancing mechanical properties. We also investigated the adhesive properties of abalone foot, which has similar nano-scale structure as that of the gecko foot. The exoskeleton of crabs is a composite consisting of highly mineralized chitin-protein fibers arranged in a twisted plywood or Bouligand pattern. A high density arrangement of organic tubules in the vertical direction stitch the structure together. We study the structure and mechanical properties of sheep crab and horseshoe crab and found the mechanical properties to be highly anisotropic due to the complex structure.

Publications:1. M. A. Meyers, A.Y.M. Lin, Y. Seki, P.Y. Chen, B. Kad and S. Bodde, Structural

Biological Composites: An Overview, JOM, July, 2006. pp. 35-41.2. M. A. Meyers, A.Y.M. Lin, P.Y. Chen and J. Muyco, Mechanical strength of abalone

nacre: Role of the soft organic layer, J. Mech. Behav. Biomed. Mat. in press 2007. 3. M. A. Meyers, P.Y. Chen, A.Y. M. Lin and Y. Seki, Biological Materials: Structure and

Mechanical Properties, Prog. Mat. Sci, in press 2007. 4. A.Y. M. Lin, P.Y. Chen and M.A. Meyers, The growth of nacre in the abalone shell.

Acta Biomat, in press 2007. 5. P.Y. Chen, A.Y.M. Lin, J. McKittrick, M.A.Meyers, Structure and mechanical

properties of crab exoskeletons. Acta Biomater, accepted 2007.

Hierarchical structure of crab exoskeletons

Research highlights:

Education:

SEM micrograph showing the Bouligand structure, pore canals, and tubules in the sheep crab exoskeleton..

Mechanical Properties and Structure of Abalone:Self-Assembled Ceramic Nanostructures

Mar Andre Meyers, University of CA, San Diego, DMR 0510138

Schematic drawing of a feather structure with SEM photographs showing rachis, barb, and barbules.

Bird Beaks and FeathersBird Beaks and Feathers

3-D image showing the hornbill beak interior. VTK (Visualization Toolkit) was used to create volume reconstruction of beak foams from 430 CT (computed tomography) scan images

Toucan and hornbill beaks are sandwich composites with an exterior consisting of multiple and staggered layers of keratin tiles and an internal core composed of a bony fibrous network of closed-cell foam. The sandwich structure of the beaks is optimized with a center hollow and is extremely light weight. We study the structure and mechanical behavior of the beak and model the mechanical response using finite element analysis. We also investigate the structure and mechanical properties of feathers and other avian materials.

FEM simulation of the toucan beak after compressive load.

Research highlights:

Education:

Experimental setup of environmental chamber system designed and built by undergraduate students.

Students in the advanced lab course (MAE171B)

designed and built a environmental chamber system

which enables mechanical testing under controlled

temperature and humidity. Toucan and hornbill beaks

as well as macaw feathers were tested in the chamber

at 36°C and 90% humidity.

Project: Design a Environmental Chamber and Measure Mechanical Properties of Bird Beaks and FeathersStudents: Brandy Pearson, Thomas Yang, Jai Parekh, Joey SorrentinoAdvisors: Prof. Joanna McKittrick

Mechanical Properties and Structure of Abalone:Self-Assembled Ceramic Nanostructures

Mar Andre Meyers, University of CA, San Diego, DMR 0510138

Mechanical Properties and Structure of Abalone:Self-Assembled Ceramic Nanostructures

Mar Andre Meyers, University of CA, San Diego, DMR 0510138

Buay Deng, an undergraduate student, conducting compression tests on the spongy samples of elk antlers

Antlers and TusksAntlers and Tusks

Optical micrograph showing the cross-section of elk antler after compression test. Osteons are deformed and shear occurred at 45°.

Deer antler is the fastest growing mammalian bone. The main function of antler is for intra-species combat during mating season. Antlers are designed to be resilient, tough and able to sustain large bending loads, making them superior structural materials. They have a similar structure to bone apart from the higher collagen content and lesser degree of mineralization. We study the structure and mechanical properties of a variety of deer antlers and try to understand the fascinating design in nature. The tusk is an extremely long mammalian tooth of that protrudes out of the mouth. We currently investigate the structure and mechanical properties of warthog and hippopotamus tusks.

Weibull analysis of tensile strength of elk antlers in the longitudinal and transverse directions.

Research highlights:

Education:

Undergraduate students who took the advanced lab course

(MAE171B) involved in the research project of biological

materials (deer antlers, hippo and warthog tusks) during

Spring quarter 2007.Design of a 3-point bend fixture for biological materialsPhuong Pham, Garrett Uyema,Bryce Nesbitt, Muntry Chan Testing mechanical properties of antlers and tusksMathew Chase, Andrew Stokes, Steve Resendez, York Cheng Design a 4-point bend fixture and for testing the fracture toughness of antlersCasper Kazazian, Garbis Kazazian, Mike Short, Alex ValdiviaAdvisors: Prof. Joanna McKittrick and Po-Yu Chen

Undergraduates Andrew Stokes (left) and Matthew Chase (right) performing tensile tests on antlers and tusks.