Wednesday, June 15, 2016

Sea Urchin Biomimicry! Echinoids Inspiring Applications from knives to glue!

Tiny teeth
Its been awhile since i've done a "What have we learned from Echinoderms?" type post.. So, this week a news round up about the utility of sea urchins and their inspired applications!

Although I talk about several different inspriations, two of the stories below focus is the elaborate jaw mechanism in sea urchins known as Aristotle's Lantern! A nice basic definition can be found at the Echinoid page on The Natural History Museum in London (here). 

Aristotle's Lantern is this weird yellow piece in the picture below. These sit over the mouth opening and the "teeth" or jaws of the sea urchin emerge through the bottom..

This illustration gives you an idea of the orientation

Image from page 201 of "Elementary text-book of zoology" (1902)

And here's a video that allows you to see the teeth emerging through the oral opening and back again. 
Urchins use these teeth to rasp algae and other food off the substrate. They are quite effective when one considers just how much algae a sea urchin eats!

ALL of the stories below are part of a field known as biomimicry!

Basically, taking the idea/engineering from ACTUAL biological structures that have demonstrated effectiveness and reverse-engineering them so that they can be used in industrial or other applications!! Urchins have been quite the inspriation of late! Here's a round up of some of the recent and more interesting ones!

1. Self Sharpening Blades/Knives! 
Based on this account in Advanced Functional Materials and a summary in National Geographic (here) sea urchin teeth were studied with x-rays and determined to occur in separate layers with different structural textures which are interlaced between softer organic layers.                                       
One of the textural layers breaks very easily but is also replaced very easily. These areas get "torn away" whenever the teeth on sea urchin jaws are used.. but are also replaced quite quickly! 

Thus, functionally, the teeth grow continuously and are thus CONSTANTLY being rejuvenated and are essentially always sharp! 










2. Sea Urchin Jaws Inspire Space Exploration??

You can also just watch this video account of the whole thing...

Here's an Italian "bionic model" of how the Aristotle's Lantern jaw might work.. Kind of similar to the way a claw in one of those arcade "grab claw" games works! 



3. Architecture: Urchin Test Shape distributes Stress! 
Its been commented upon at sites such as these that the "oblate" shape of sea urchin skeletons (i.e., the test) is very effective at distributing stress evenly over the surface. Thus, the shape of urchin skeletons might actually be useful for inspiring better shapes in building! 
urchin test
...and then of course, there's the TARDIS in Doctor Who! 


4. Sea Urchin Spines Inspire Idea for Concrete! 
A paper by Seto et al in PNAS from 2012 studied the physical structure of sea urchin spines and discovered that they were composed of crystals that were bound together with a second type of calcium carbonate, acting as sort of a mortar, but with no crystal structure. These give the spines a highly resistant texture that suggest a better way to make fracture resistant materials.  A summary of this was in this BBC story.  and yet even more can be found on this blog about Mesocrystals and concrete! 
Sea Urchin spines
5. Adhesives!
Amazing sea urchin tube feet

Instead of "suction" as had been believed for decades, it turns out that urchin tube feet work on a chemical adhesive basis! In other words,, they STICK instead of SUCK!  You can go through a brief summary of these details here. 

These provide a lot of potential for marine adhesives if the means of adhesion can be understood and "reverse-engineered"!

Other posts in the "What good are echinoderms" series to be found HERE   
and here