Learning from sharks to combat microplastics
Samantha is taking biomimicry to the seas and specifically to sharks, looking to learn from the flow dynamics of their spiral intestines. Her aim is to use the engineering inspiration from nature to remove microplastics from flowing water. The project will involve using particle image velocimetry (PIV) to investigate the flow dynamics of particles moving through 3D printed models of a shark’s spiral intestine. Samantha then hopes to design and 3D print an optimised shark spiral intestine to sort and remove microplastics, and then scale it up to work with waste water treatment and storm-water run-off.
Samantha Leigh
I decided I wanted to be a marine scientist in the third grade, when I was assigned a diorama project on the ocean. I got to interview a real marine scientist and I was hooked! I grew up in Bel Air, a town just north of Baltimore, Maryland. As a high school student, I volunteered at the National Aquarium in Baltimore and then went on to earn my BSc degree in marine science with an environmental science minor from Coastal Carolina University. I later earned my MSc and PhD from the University of California, Irvine,...
Visualization of Flow Through Shark Spiral Intestines
The aim of this project is to quantify the flow dynamics created by four different shark spiral intestine morphologies in order to design an optimised Tesla valve-style filter that will effectively remove microplastics and other micro-sized solid debris from flowing water without the use of mechanical parts.
Currently, there is no mechanism in place to target the removal of microplastics despite the fact that they are pervasive throughout ocean environments. This project firstly will teach us more about how sharks process the food they eat, and secondly has the potential to help solve a serious pollution problem facing the word today.
Chondrichthyans (sharks, skates, rays and chimaeras) possess a unique intestine in the mid-region of their digestive tract called a spiral intestine. It consists of a varying number of intestinal tissue folds (2–50) and has been observed in four main morphological forms: columnar, scroll, funnels facing backward and funnels facing forward. It is supposed that the spiral intestine expands the surface area and volume of the intestine compared to a straight gut, allegedly increasing the length of time the material being digested spends in the gut and the amount of nutrients it absorbs. However, very little is known about the mechanical way in which this material flows through the spiral structure. To date, I have collected spiral intestines from 32 shark species spanning 22 families. I created 3D constructions from CT scans of the intestines that enable us to visualise the structure of the tissue folds in the spiral intestine and compare its morphology in different species without dissecting it. I also measured the average flow rate for water and varying viscosities of glycerol (to mimic the viscosity of the material being digested) in each of the four spiral morphologies. The results suggest that spiral intestines may act as natural Tesla valves, preventing backflow without flapper or constrictive valves and therefore encouraging flow in one direction only. Hence, spiral intestine morphologies should be explored further as mechanisms to produce one-way flow without the use of mechanical parts, which could have a multitude of practical purposes, such as filtering out microplastics from storm water and waste water. Currently, no mechanisms are in place to prevent microplastics from making their way into the ocean, where they can be consumed by organisms and potentially cause intestinal blockages, leaching of toxicants and growth or fecundity issues, among others. An optimised spiral intestine design may be capable of removing microplastics from flowing water without energy input.
- To use particle image velocimetry (PIV) to quantify the flow dynamics of particles of varying sizes through 3D printed models of spiral intestines of sharks.
- To design and 3D print an optimised model of a shark spiral intestine capable of sorting and removing microplastics from flowing water without the use of mechanical parts.
- To scale up the filter design so that it can be used in the treatment of waste water and storm-water run-off.