Step-by-step tutorial
Step 1
Cut three pieces of string, each about 15 inches long.
Step 2
Cut a notch 1 inch below the top of each straw.
Step 3
Thread a piece of string through each straw. Tape the end of the string to the top of the straw.
Step 4
Trace this shape onto your cardboard. (It doesn’t have to be perfect!) Just make sure the blue rectangles on the template run in the same direction as the ridges in the cardboard.
Step 5
Cut the shape out of the cardboard along the dashed lines in the illustration.
Step 6
Crease the cardboard along the green lines in the illustration.
Step 7
Tape a straw onto each blue rectangle so that the bottom of each straw touches the green line. Make sure the notches are facing up.
Step 8
Fold the cardboard inwards along the long green lines to make a triangle. Tape the flap closed.
Step 9
Fold the three top flaps outward to separate the straws.
Step 10
To use your robot hand, hold onto the cardboard section and pull on the strings. Try to grab some small objects with the straw fingers! Try pulling all the strings at once or one at a time. What makes it easier to pick things up? Now try looping rubber bands onto each straw finger. Can you grab more things that way?
Fact
A design challenge like this grabber seldom works perfectly on the first attempt. So get ready to try it, test it, tweak it, and repeat it — until you get it right.
Engineers have a name for this process: iterative design. They use it to try out solutions,
learn, and improve — just like you're doing.
To improve your grabber, you might want to make it more precise, so it can pick up something teeny-tiny. You could test out smaller straws, or make the straw “fingers” shorter, or make the cuts in a different place.
Or you might want to make your grabber super strong, so it can pick up heavier objects. You could try getting rid of the straws entirely and make the “fingers” out of cardboard.
And the best part of iterative design? There’s no such thing as a mistake! Every test — whether it works or not — is a chance to learn something new. Try it and see!