Extended Abstract: Making a Mechanical Hand with Plastic Drinking Straws

Abstract

Hi, my name is Sowmya Natarajan and I will be presenting a mechanical hand made from plastic drinking straws. The objective of this project is to pick up objects using the fingers. I will have 5 strings controlling 5 different fingers. The fingers are able to pick up objects such as crushed paper into a ball. I got this idea from my aunt who suggested it, she was telling me how it corresponds to prosthetic arms. I was inspired that I could replicate something so high-tech from everyday materials like plastic straws and string. It works like a prosthetic hand, as you pull the springs the straws curl like your joints in your fingers. If I put the hand in a pair of gloves, it can pick small things. The hand is very fragile and something as little as pulling the dental floss too hard can cause the string to detach from the straw. While working on this project, I came across many challenges, and during those challenges, I developed questions. To make the hand Step 1 Gather all your materials Step 2 you need to cut three holes in the straw which would be used as the joints. Please note that the size of the holes matters very much. Also the distance between each hole matters. Step 3 you would get a piece of string and pull it through the straw, do not pull the strings through the holes just put it in the straw. Step 4 you pull the string from the bottom and all three joints should move. Joints are critical in hand movement. In my prosthetic hand, the joints are represented by holes. My questions were if you cut the holes in the hand the same size will the hand still work? If you cut the holes larger will the hand still move all the joints? If you cut the holes closer/farther together will it function better? This work builds upon the scholarship of many individuals. These individuals include the Harvard lab where George Whitesides and Alex Nemiroski reinvented “soft robots”. They were inspired by arthropod insects that can walk, stand, and were able to move on liquid surfaces. Soft robots have a lot of work to be done but in the future, they could help with search and rescue missions and are able to swim in the water. These soft robots are made out of plastic drinking straws. The first time I made the hand all the joints didn’t move. I wasn’t sure why, but as time passed and I found other ways to make the hand I realized that I cut the holes too big. The second time I tried making the hand I cut the holes too close together and too small. After many tries, I realized that the first hole needs to be the largest hole the middle ho/le needs to be medium-sized and the lowest hole needs to be the smallest.