Page 30 - IB December 2021

Prosthetic fins for

INJURED SEA TURTLES

Researchers from the AUT BioDesign Lab have developed a pros- based on real sea turtle geometries.
thetic fin to rehabilitate injured sea turtles. The roboturtle’s head and front flippers were coloured red to make
Healthy oceans need sea turtles, but they are unfortunately fre- its swimming performance easier to capture.
quently injured by human factors such as boats and fishing nets, with Roboturtle’s swimming mode was then tested against the theoreti-
all seven species now endangered. A damaged fin limits swimming cal models, using motion sensor cameras in AUT Millenium’s olympic-
range and survival and prevents female turtles from returning to land sized pool with the assistance of High-Performance Sport New Zea-
to lay eggs. A successful prosthetic fin, attached to the turtle’s humerus land and GoldMine.
by stem implant, would play an important role in the protection of en- The design has been approved for clinical trials and four stems have
dangered and threatened keystone species. been sent to the Canary Islands, Spain to be inserted into living turtles.
The project involved the development of four-dimensional turtle Because the turtle must match the size of the prosthetic for it to
fin kinematics and optimisation of the fin geometry to bio mimic the function correctly, it is currently being trialled in one turtle, Vivo, at the
movement of a real fin. It was developed by PhD student Nick van der CRFS Centre for the Recovery of Wild Fauna, Tenerife, Canary Island.
Geest during his mechanical engineering degree under the supervi- The Byron Bay Wildlife Hospital in Australia has also approached
sion of Dr Lorenzo Garcia. AUT to develop a further collaboration, in addition to the New Zealand
Nick and Dr Garcia first created mathematical models of the three Centre for Conservation Medicine (NZCCM), based in the Auckland
main swimming kinematics of the turtle. Using the models of general Zoo. NZCCM already being has collaborating with Dr Garcia to design
swimming, power stroke, and vigorous swimming, Nick then created surgical tools and veterinary equipment.
a series of prototypes, to validate the models and determine the best While Nick would like more sea turtles to be part of the trial, Nick
design. must wait for injured animals that are the right size for the implants he
“I had to determine whether or not a simple geometry would work has made, thanks to the support of Zenith Tecnica who manufactured
to make the manufacturing process simpler,” says Nick. “My models the 3D-printed components.
showed nature’s original design works best, around two to three times “Normally you’d receive the injured turtle, measure it and make an
more efficiently than the other shapes we tested.” implant to fit,” Nick says. “It’s really important that the implant matches
The design moved from a rectangular shape to an air foil shape be- perfectly.”
fore arriving at the optimised design. The final design is composed Nick says the ideal next steps, once trials are completed, is for wild-
of a molded polyurethane rubber fin, cast over a 3D-printed skeletal life rescue centres and veterinarians around the world to be able to
system made from titanium alloy, which is implanted into a turtle’s hu- print new prosthetic fins to fit the turtles recovered. The proliferation
merus bone via a stem implant procedure, similar to a hip implant on a of 3D printers will continue to put the prosthetic flipper within reach
human. Each design was tested on the “Turtle fin Dyno” Nick designed of veterinarians. The researchers are currently working on publishing
with the help of MAG Assembly LTD and PSP Limited. Nick says this their results in scientific journals to reveal their finding, and to open-
was a very important part of the process to ensure the initial estimates source the designs so the information and processes fully available.
were good before moving to the next stage. Nick’s design has been well received and widely popular but as testing
A robotic turtle was designed and built to validate the design by progresses, he will continue to refine it.
comparing simulation data to that of the robots swimming. The robotic The AUT BioDesign Lab is working to apply what Nick has learnt
turtle ‘roboturtle’ was 3D-printed from CAD models created by Nick, about sea turtles into other fields.

30 Islands Business, December 2021