Sea urchins inspired a strong new medical staple
PHOENIX, Ariz. — Sea urchins can be a pain in the, er, foot. These round critters are coated in defensive spikes. When a bigger animal tries a mouthful — or an unsuspecting human takes an unlucky step — they quickly realize their mistake. The urchin's spines sink in and are notoriously difficult to get out. But three teens saw this animal’s protective technology as something that could aid medicine. They used it to design a way to staple wounds shut.
Sometimes, doctors and nurses will close a big cut with stitches or glue. But other times, they turn to staples. Surgeons can put them in quickly. And wounds that are stapled shut can heal faster than those closed with stitches. But no medical device is perfect. Chae Ryeon Lee, 17, learned that staples could fall out, leaving wounds vulnerable to infection. That inspired the 10th grade student at Incheon Posco Academy in South Korea to start a project with her school science club to redesign medical staples.
At the same time, fellow club member Esther Ji Young Lee, 16 — a junior at the school — was learning about sea urchins. She saw a video about how their spines didn’t come out easily. Curious, she wanted to learn more about them. Esther and Chae began sharing ideas. With the help of Jaewoo Song, 16, and other members of the science club, the teens decided to see if sea urchin spines might offer clues to the design of better sutures.
They started by looking closely at sea urchin spines.
“I tried to use a microscope at school,” Esther says. But no matter how hard she tried, she couldn’t see the spines in enough detail. Her team eventually got to use a scanning electron microscope, or SEM, at Yonsei University in Seoul. This instrument scans the surface of a specimen with electrons. Those that bounce off the object form an image. The SEM imagery brought the urchin spines into crisp detail. Each, they found, had many tiny barbs branching off it. Once the spine was in someone’s foot, those barbs would all but lock the spine in place.
That inspired the teens to put similar backward-facing barbs into their staples. It would let them hook into skin and stay there.
Printing for points
The design wasn’t simple, Chae explains. The students had to figure out what the best barb structure would be. They also had to decide how many barbs to put on the staple’s shaft and what angle from that shaft would best anchor them into tissue.
At first, the team tried to make a model of their staple by cutting off the tips of plastic pipettes — fluid collection tools — by hand. But they couldn’t design their model in enough detail.
Then Jaewoo began working with a 3-D printer — a printer that lays down layers of plastic to build an object. But the 3-D printer couldn’t print staples tiny enough to work. The team compromised with a model of what they wanted, one that was about five times larger than the staples they eventually hoped to make.
They built some of their models with two barbs. Others had three. They tried wide barbs on the end. They also tried narrow barbs pointing backward, like arrowheads. Each time, they investigated how much force it took to tear their “staples” out of some artificial skin that they had purchased online.
They didn’t have a scientific tool to measure their pulling force. So they made one out of a pulley in the ceiling of their school and a force meter. It took 3.9 newtons to yank out a normal medical staple, they found. Adding barbs increased the force needed to remove the staples. If the barbs stuck out a little — at an angle of 20 degrees from the staple — they were even harder to yank free of the skin.
Their best sea-urchin-inspired staple had three extra barbs along its length. Each barb pointed exactly 20 degrees out from the staple. This design required 11.8 newtons of force to yank out of their artificial skin.
The teens brought their 3-D printed staples to the Intel International Science and Engineering Fair. This competition was created in 1950 by Society for Science & the Public, which still runs ISEF. (The Society also publishes Science News for Students.) This year’s fair, which was sponsored by Intel, brought more than 1,800 students to Phoenix from 80 countries.
For this year’s project, the Korean teens focused on the physical parts of the sea urchin barb, Jaewoo explains. But they aren’t done. Now, he says, they want to focus on the chemical aspects. After all, if a staple sticks in really well, getting it out could be a real pain. The team hopes to design a staple that will eventually dissolve in place once the wound is healed. If it works, that nasty sea urchin sting might one day end up inspiring something that saves patients a lot of pain.
angle The space (usually measured in degrees) between two intersecting lines or surfaces at or close to the point where they meet.
chemical A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O.
degree (in geometry) A unit of measurement for angles. Each degree equals one three-hundred-and-sixtieth of the circumference of a circle.
dissolve To turn a solid into a liquid and disperse it into that starting liquid. (For instance, sugar or salt crystals, which are solids, will dissolve into water. Now the crystals are gone and the solution is a fully dispersed mix of the liquid form of the sugar or salt in water.)
electron A negatively charged particle, usually found orbiting the outer regions of an atom; also, the carrier of electricity within solids.
force Some outside influence that can change the motion of a body, hold bodies close to one another, or produce motion or stress in a stationary body.
infection A disease that can spread from one organism to another. It’s usually caused by some type of germ.
Intel International Science and Engineering Fair (Intel ISEF) Initially launched in 1950, this competition is one of three created (and still run) by the Society for Science & the Public. Each year now, approximately 1,800 high school students from more than 80 countries, regions, and territories are awarded the opportunity to showcase their independent research at Intel ISEF and compete for an average of almost $5 million in prizes.
microscope An instrument used to view objects, like bacteria, or the single cells of plants or animals, that are too small to be visible to the unaided eye.
model A simulation of a real-world event (usually using a computer) that has been developed to predict one or more likely outcomes. Or an individual that is meant to display how something would work in or look on others.
newton A unit of force named for Sir Isaac Newton, a 17th century English physicist and mathematician. One newton is an amount that would give a mass of one kilogram an acceleration of one meter per second per second.
physical (adj.) A term for things that exist in the real world, as opposed to in memories or the imagination. It can also refer to properties of materials that are due to their size and non-chemical interactions (such as when one block slams with force into another).
pipette A fluid-collection tool used in chemistry and some biology labs. It may consist of just a thin tube into which fluid is drawn by suction. Once the fluid is inside, the top is closed to hold the liquid inside until someone is ready to dispense it.
scanning electron microscope (also known as SEM) A scientific instrument in which the surface of a specimen is scanned by a beam of electrons that are reflected to form an image.
sea An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.
suture A stitch or row of stitches holding together the edges of a wound or surgical incision.
three-dimensional (3-D) printing The creation of a three-dimensional object with a machine that follows instructions from a computer program. The computer tells the printer where to lay down successive layers of some raw material, which can be plastic, metals, food or even living cells. 3-D printing is also called additive manufacturing.
urchin Small, spine-covered sea animals without eyes or limbs which are related to sand dollars and starfish.