Water-Powered Cardboard Robot Arm Challenge
⚠️ Safety Warning
Adult supervision needed for hot glue gun and scissors. Be careful with brass fastener points.
All experiments require adult supervision.
Materials You'll Need
Gather these 8 items before starting
💡 Tip: Check off items as you gather them to stay organized!
Step-by-Step Instructions
Follow these 8 steps carefully
cut 3 cardboard strips: 20cm, 15cm, and 10cm long, each 5cm wide.
Score fold lines across each strip to create finger-like joints.
Connect the three strips end-to-end using brass fasteners to create hinged joints.
Cut drinking straws into 3cm pieces and glue them in a line along one side of each strip.
Thread a piece of string through all the straw pieces from tip to base.
Pull the string at the base — the arm should curl up like fingers closing!
Add more strings for more independent joint control.
Mount the arm on a base and try picking up lightweight objects.
✅ Remember: Take your time with each step and ask an adult for help if needed!
The Science Behind It 🔬
Your cardboard robot arm mimics how real tendons and muscles work in your hand! The strings act like tendons — strong cords that connect muscles to bones. When you pull a string (like a muscle contracting), it pulls the joint closed. Real robotic arms in factories work on similar principles, using cables, hydraulics, or electric motors to control each joint. Engineers must carefully design the placement of each string/cable to get precise movement. This is the field of biomechanical engineering — designing machines inspired by biology! This concept connects to many other areas of science, including astronomy, medicine, and environmental science.