The aim of this protocol is to examine the natural structure of the sea urchin mouthpiece, Aristotle's lantern, to develop a sediment sampling prototype using engineering analysis to test the application of biological features in bio-inspired designs. This method can help answer key questions in the bio-inspired design field. Specifically why did a keeled tooth structure evolve in sea urchins and how might it be useful for sediment sampling.
The main advantage of this technique is that it provides a general framework for bio-inspired design investigations of various natural structures. Other such structures include the seahorse tail, the scutes of the boxfish, and the spines of the porcupine fish. The implications of this technically makes enhancement a proprietary surface expoloration because mineral poles are fit with bio-spar sediment samplers can efficiently collect a little samples.
Generally individuals new to this method will struggle because objectives for each bio-inspired protocol will vary depending on the type of natural structure examined. After thawing the sea urchin, set it up for dissection with the tips of the teeth pointed up. And start cutting away the connective tissue around the perimeter of the Aristotle's lantern.
Then, carefully lift out the lantern and rinse it off with running distilled water. Use forceps to remove remnant tissue on the outside and carefully open the lantern to extract the teeth. Alternatively, a dried lantern that is rinsed off again with water will fall apart to allow for easier access to the teeth.
Now, pick up a tooth and carefully submerge it in a tube of freshly prepared epoxy. Position the curved concave side facing up and do not let the tooth touch the tube wall. Then, let the epoxy cure at room temperature for 24 hours.
The next day, use a sectioning saw to remove the epoxy around the tooth down to about one cubic centimeter. Then, with a piece of coarse sandpaper number 125 or higher and using light pressure, rub the sample in one direction for five minutes. Progressively change to finer and finer grit sandpapers, up to the number 2400.
For each sandpaper grit, make sure to rotate the sample 90 degrees. Use a microscope as needed to verify that the rubbing is always in the same direction for each sandpaper grit. After the sanding, moisten a microcloth with a 50 percent by volume half micron aluminina polish in water.
Then rub the sample in a back and forth motion for five minutes. After polishing use particle-free tissue paper to clean off the sample, and then wrap it up in the same paper for storage. Next, characterize the tooth's microstructure using scanning electron microscopy.
After applying a sputter coat, take 250 to 500x micrograph images of the sample. Next take microcomputed tomography scans of the whole pink sea urchin and the freshly dissected Aristotle's lantern. Place the samples over a moistened tissue when in the imaging chamber.
For the body, scan with an isotropic voxel size of 36 microns at 100 peak kilovoltage and 100 milliamps. For the lantern, scan with an isotropic voxel size of about nine microns at 70 peak kilovoltage and 141 milliamps. Use a one point zero millimeter aluminum filter for both.
Using micro CT scans and CAD modeling a bio-inspired design was produced with five curved teeth with a height of six centimeters and a diameter of eight centimeters for the closed lantern, which is five times larger than the natural Aristotle's lantern. For each component of the bio-inspired jaw produce STL files for 3D printing. Prepare the 3D printer by first loading acrylonitrile butadiene styrene plastic, and support plastic material cartridges.
Then insert the modeling base onto the z platform by first aligning the tabs on the base with the slots in the tray. Now open the STL file parts and follow the display screen steps to orient and print individual lantern parts at the same time. Shown here is an example for 3D printing a joint arm.
After printing the files, release the modeling base from the tabs and slide the base out of the printer along the tray guides. Then, use a metal spatula to pry the printed parts off the base. Once detached, place the printed parts into a heated base bath until the support plastic material dissolves.
Now, fasten each tooth to a joint arm with a link rod using e-retaining rings on either side and assemble the bio-inspired Aristotle's lantern. Using the CAD file for the bio-inspired tooth perform a finite element modeling stress analysis test. First, open the file.
Start a new study. And choose to run a static test with a fixed geometry. Then, click on the interfaces to add fixtures to the mounting holes where the pins will go.
Next, set the force of the external loads. Click on the tooth grinding tip faces to apply a 45 Newton force to the edges. Now, set the gravity.
Indicate in the top plane setting that the gravity force should be applied normally to the plane. Next, create a mesh on the design surface, and set the mesh density to fine. Now, run the test to compare between a tooth with and without the keel.
A colored scale will show the areas of highest stress. Non-invasive imaging of the sea urchin tooth and the Aristotle's lantern were instrumental in producing a bio-inspired design. Detailed analysis of the tooth's microstructure by SEM confirmed the structural importance of the magnesium-enriched stone part in the tooth grinding tip.
Plate and fiber primary elements are connected together by a matrix of secondary elements in the hardest stone region of the tooth grinding tip. The harder stone portion shown in darker gray, is composed of up to 40 percent magnesium atoms which replace the calcium atoms. Thus, the bio-inspired lantern was designed with CAD software, 3D printed and assembled.
The ultimate purpose of the design is to collect sand. The importance of the keel in the design was tested using computerized stress tests on the CAD design. For 45 Newton applied force, the maximum stress experienced by the keeled tooth design was about 16 percent less.
However, the keel adds only four percent to the mass of the design. When attempting a bio-inspired design protocol, it's important to start with careful observation of the natural structure in its living form, or through usage of non-invasive characterization methods, like micro CT and SEM. Following the general procedure, bio-inspired designs from other natural structures can be implemented in useful applications in a wide range of engineering fields.
The final bio-exploration step based on the work of Professor Michael Porter, is especially essential for using engineering analysis methods to quantify the mechanical advantage of the keel structure in the sea urchin tooth.
