The Defend-A-Band

by Srinidhi Gubba

8th Grade at Meadow Park Middle School (Beaverton, OR)

Second Place

“Breaking News! A Salem woman missing after going for her morning jog. Stay tuned for more information.” says the women behind the T.V. screen. Not again. All the woman did was go on a run, and now she is torn away from her poor, scared family. “Things like this can happen Nalla, and defending yourself is all you can do.” says the voice behind me. Turning around, I see my mom casually cutting vegetables, as if the news is normal. I realize she’s right, things like this happen a lot. In fact, more than 50% of women runners under 30 have been harassed one way or another. What could possibly help women defend themselves?

Thinking about these events is truly frightening. I need to get something protective in case I’m a situation like this. Scrolling through many websites, I notice that most of the defense mechanisms available have to do with weapons, like knives. It might help, but I want something that temporarily stops a person, instead of requiring me to fight back as I have no experience. That way, I have more time to escape. It should be easily disguised as well, and capable of being used in less than 5 seconds. Though I keep searching, there is nothing that suits my requirements. There are products that use pepper spray, but that’s their only purpose. The most effective solution I have right now is making something myself.

After doing my final research, I have come down to 3 main requirements for my solution:
1) The defense mechanism should be hidden within an everyday item
2) The exterior of the everyday item should benefit for attacking in case necessary
3) The spray should work for at least a one meter radius

The reason I chose these requirements is because they help guide the transformation of an everyday item into a defense system both on the outside and within the item. I’ve created two ideas, a water bottle and bracelet, but I don’t know which one is best. Let’s make a reasoning list.

Both ideas are effective solutions for my problem, but since a bracelet can easily be worn at all time compared to carrying a water bottle, I decided to go with my first idea. Also, since I am limited on materials, making a band uses less material compared to a water bottle. Now, my favorite part-- prototyping!

The first place I head to is my garage. Looking around, I find many helpful materials. My mom loves to make statues and showpieces, so there’s a variety of options. She’s actually a mechanical engineer and currently is using solar panels as an alternative energy source. I’m proud to tell people that her innovative ideas are making the world a better place. She has a lot of clay, but clay can easily break once dry, so not a good idea. As I turn around losing hope, I notice a small dusty box with the word FILAMENT on it. It must be a 3-D printer material. Hmm… I could use that and make a bracelet with holes to put pepper spray vials in. All I have to do is design it!

After tons of measuring, My design is born. It’s a torus shape with two holes for spray vials. I used mini pyramids to create the bumps for the exterior defense. I chose to use acrylonitrile butadiene styrene to make it, as it’s a strong and durable filament. Once I printed it, I glued in the vials with water in it. It’s easy to test afterward by using water to represent pepper spray for self defense. All I need to do is have the glue dry and I am onto testing.

My shining blue bracelet is all done! The vials have fit in well. To test it, I am using a paper with a 10 centimeter radius target. For every ½ meter, I will see if the spray can get the majority of water on the target. Dying the water will make it easy to tell if the spray worked.

As I continue to set up, I use tape to mark the distances. I put the band on my wrist, which fits comfortably. For the first ½ meter, I squirt the liquid 3 meters high, the exact same height of the center of the target. The entire splash of water made it in the target! That would be 100%. Immediately, I put a new target on the board, and step to the one meter mark. With another squirt, I get all of it in the target, but it’s more spread out. On the other trial, the water was all in one place. Another 100%. For the 3rd ½ meter, all the water reaches the paper, but only ¾ of it is in the target. So, 75%. If it goes below 50%, it is not effective for that specific distance. For meter two, the spray didn’t do as good. Majority of the water made the target, but the rest didn’t reach the paper. This is about 60%, meaning it is still effective. This was the last distance the bracelet worked successfully. For 2 ½ meters, it got about 40% of the target, not matching my goal. I repeated the test from the start 4 more times, and 4 out of the 5 times the maximum distance was two meters, while for the other one it was barely 2 ½ meters.

Based on my data, I can say that this bracelet is successful for a 2 meter radius. This is double my expectation, meaning it can help someone protect themselves temporarily. For the other two requirements, the spray bottles were hidden well, just showing the cap part on the bracelet. For the exterior, I have a durable and strong filament, acrylonitrile butadiene styrene, which means it is effective as a defense mechanism. So with all my requirements passed, I can go show this to my mom!

As I explained my design and finished product to my mom, she seems captivated. I made sure every detail had a purpose, making it an effective self defense bracelet. “Nalla, you did an amazing job! It’s good you want to be an engineer who helps people. I think we can improve it by adding metal pyramids to make it stronger since 3-D printing can be fragile. Otherwise great,” she says as she hugs me. I hope to make my design even better and maybe add in some computerized technology too. This is just the beginning to a great invention, and I love being an engineer so much!

Annotated Bibliography