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(1a) Stingray Injury
There are two current methods that beachgoers are encouraged to use so as to avoid being stung. One is the "Stingray Shuffle", where one would keep their feet on the sea floor and shuffle forward to dislodge any possible stingrays hiding in the sand. This method is quite unreliable because it fails to protect people from being stung if no stingrays are dislodged.
The other method would be to invest in stingray guards or water booties. These offer adequate protection from penetrating barbs but are not made to wear for doing common beach activities; rather, these were made primarily for fishermen.
Background
Background
There are thousands of people being stung by stingrays each year in the United States. In particular, the most common stingray species found in Southern California is the round stingray. These rays typically prefer to hide and live in the shallows at the beach. Due to their non-aggressive nature, they only sting in self-defense, thereby shooting and puncturing the victim’s foot with a pointy barb attached at the base of their tail. The barbs are extremely sharp and coated in a non-fatal venom that causes immense pain. If left untreated, the victim's wound(s) may become infected and/or inflicted with flesh necrosis.
(1b) Round Stingray
Objectives
The fundamental objective of this project was to create a product that can prevent people from being stung by stingrays. Two paths were considered towards accomplishing this: (1) a deterrent that would eliminate the possibility of a stingray getting close enough to harm people, and (2) protective footwear that would prevent a barb from penetrating skin. Due to lack of available research and access to stingrays, it was determined that the more feasible path to pursue was protective footwear.
In the process of searching for suitable materials to use, greater significance was placed on a material's ability to resist penetration by a stingray barb rather than the material's comfortability, wearability, and marine functionality. Once the protection criteria was fulfilled, the project became focused on making sure the product was user-friendly for beach activities like surfing, walking, playing in the sand, etc.
(2a) Anatomy of a Stingray Barb
(2b) Impulse Testing
The video above demonstrates how a stingray flicks its tail up to launch its barb at any threat it detects. The device it is hitting with its tail was used to measure and collect data regarding the impulse of the flicking action.
Final Design
The components that formed the Sole Survivor are: neoprene, rubber, 3D-printed hexagons, hot glue, a 22.86 cm long zipper, and a velcro cinch strap.
(3a) Components of the Sole Survivor
A layered combination neoprene and rubber, as shown in Figure 3a, provided the necessary amount of protection against a stingray barb. Because neoprene is already commonly used in wetsuits, it fulfilled the comfortability and form-fitting criteria for a footwear item.
Next, the insole was cut out of a rigid, yet semi-flexible composite sheet of 3D printed PLA-linked hexagons. More flexibility was needed for the sole to allow proper movement, however, so the PLA was then encased in hot glue, a thermoplastic adhesive.
Last of all, the zipper and velcro strap worked together to make sure that the Sole Survivors were easy to put on and stay secured without fear of it slipping off of the user.
(3b) Left Side View of the Sole Survivor
(3c) Right Side View of the Sole Survivor
Results
The following results of the final design solution were determined by having the Sole Survivors undergo both rigorous puncture-resistance and functionality field tests.
Simulation of a stingray flicking its barb for the puncture-resistance test was achieved through the use of a pendulum set up as shown in Figure 4a. The Sole Survivor's layered combination of neoprene and rubber allowed it to withstand being punctured by both dull and sharp stingray barbs at max force generated by the pendulum arm.
The PLA hexagonal insole not only proved to be extremely resilient to dull and sharp barbs at max force but also to the worst-case scenario of stepping directly onto a barb. In the video shown below, team member Miles jumps up first in order to increase the amount of body weight being forced onto the sharp barb from above. The barb completely shattered and left small shards stuck in the sole but the sole's structural integrity was not compromised in any way.
(4b) Stomp Test
(4a) Pendulum Simulation
Once the Sole Survivors survived being repeatedly punctured by sharp stingray barbs, they were put through a field test at the beach since that was the environment for its intended usage. They graded extremely well using the following criteria on a scale of 1 to 5 (indicated in Figure 4b): putting on, top contour, bottom contour, feel of the sole, bending, standing, even ground, sand (wet and dry), ocean, and drag.
Senior Design Day Presentation
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