Excessive bleeding is, in some sense, an engineering problem.“For us, everything is a machine, even a human body,” says Hyunwoo Yuk, a research scientist in mechanical engineering at MIT. “They are malfunctioning and breaking, and we have some mechanical way to solve it.”
About 1.9 million people die every year from blood loss, sometimes from trauma, sometimes on the operating table. Bleeding bodies are wet, prone to infection, and need urgent care. Yet it’s hard to create a seal on wet tissue, and most commercial products used to stop dangerous bleeding rely on coagulants which take minutes to work. Some people don’t have minutes.For the last seven years, Yuk’s team has been developing an entirely different approach to stopping bleeding: glue. More specifically, glue inspired by barnacles. Yuk says barnacles hold an evolutionary solution to the problem of sticking to surfaces that are resistant to getting stuck. In a study published this month in Nature Biomedical Engineering, his team demonstrated how this arthropod-like glue can stop bleeding in seconds.
In the experiment, Yuk treated rats with bleeding heart and liver injuries with products typically used by surgeons. No dice—the bleeding continued. On others, he squeezed on the lab’s oily paste. “Exactly the same injury could be sealed in just 10 seconds or so,” he says.The rats survived thanks to the glue, and so did pigs that were tested by Yuk’s collaborators at the Mayo Clinic. Their evidence, although still preliminary, bodes particularly well for human surgical patients with blood, heart, and liver disorders. “My overall impression of this material is that it's incredible,” says Hanjay Wang, a resident in Stanford University’s Cardiothoracic Surgery Department who was not involved in the study. “It definitely fills a need, especially in the emergency setting, when you need to just get control.”
The team of engineers knew they might find inspiration in the animal world. “The driving force for nature's evolution is survival,” Yuk says. If you want to solve a problem, you can probably find an animal that’s already evolved to solve it. Barnacles caught their attention, he says, because they are annoyingly sticky: “It's sticking on rock, sticking on rusted steel, it’s sticking on slimy surfaces like whales and turtles.”
Barnacles cling thanks to a cement of proteins secreted from glands along each animal’s “forehead.” But the secret sauce—well, more of an oil—is a cocktail of lipids that first sweep contaminants away from surfaces so the proteins can do their thing. “So basically they are terraforming the target substrate,” Yuk says, priming it for a fast, strong seal.
And it turns out that you need a similar superpower when trying to seal up bleeding animal tissue. In a way, says Yuk, blood is a “contaminated fluid” because it’s not a homogeneous liquid—it’s filled with blood cells. For an adhesive to work, you’ve got to shove those cells out of the way.
Instead of using actual barnacle proteins for their test glue, Yuk’s team referred to it as a kind of chemical rubric for devising a high-pressure physical barrier. In place of sticky protein particles, they repurposed a previous lab invention: biocompatible adhesive sheets made from a cocktail of organic molecules, water, and chitosan—a sugar found in hard shellfish exoskeletons. (Barnacles use a similar compound called chitin , and chitosan is already used widely in wound dressings .) Then they tossed the sheets into a cryogenic grinder that pulverized them until they turned into shards roughly one hundredth of a millimeter across.