Peter Means for Virginia Tech
Postdoctoral researcher Zian Jia examines a 3D-printed model of cuttlebone ’ s microstructure .
to depths as low as 600 meters . The animal adjusts the ratio of gas to water in that tank to float up or sink down . To serve this purpose , the shell has to be lightweight and porous for active fluid exchange , yet stiff enough to protect the cuttlefish ’ s body from strong water pressure as it dives deeper . When cuttlebone does get crushed by pressure or by a predator ’ s bite , it has to be able to absorb a lot of energy . That way , the damage stays in a localized area of the shell , rather than shattering the entire cuttlebone .
The need to balance all of these functions is what makes cuttlebone so unique , Li ’ s team discovered , as they examined the shell ’ s internal microstructure .
Ph . D . student and study co-author Ting Yang used synchrotron-based micro-computed tomography to characterize cuttlebone microstructure in 3D , penetrating the shell with a powerful X-ray beam from Argonne National Laboratory to produce high-resolution images . She and the team observed what happened to the shell ’ s microstructure when it was compressed by applying the in-situ tomography method during mechanical tests . Combining these steps with digital image correlation , which allows for frame-by-frame image comparison , they studied cuttlebone ’ s full deformation and fracture processes under loading .
Their experiments revealed more about cuttlebone ’ s chambered “ wall-septa ” microstructure and its design for optimized weight , stiffness , and damage tolerance .
The design separates cuttlebone into individual chambers with floors and ceilings , or “ septa ,” supported by vertical “ walls .” Other animals , like birds , have a similar structure , known as a “ sandwich ” structure . With a layer of dense bone atop another and vertical struts in between for support , the structure is made lightweight and stiff . Unlike the sandwich structure , however , cuttlebone ’ s microstructure has multiple layers — those chambers — and they ’ re supported by wavy walls instead of straight struts . The waviness increases along each wall from floor to ceiling in a “ waviness gradient .”