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Build a robotic hand

Build a robotic hand
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Build a simple tendon-driven robotic hand from cardboard, straws, string, and tape; learn about joints, levers, and grasping while testing different objects.

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Step-by-step guide to build a robotic hand

What you need
Adult supervision required, cardboard, drinking straws, pencil, ruler, scissors, string, tape

Step 1

Gather all the materials and clear a flat workspace to build on.

Step 2

Place your hand on the cardboard and trace around it leaving extra cardboard at the wrist for a palm base.

Step 3

Cut out the traced hand shape from the cardboard using scissors.

Step 4

Draw two short lines on each cardboard finger to divide each finger into three equal segments for joints.

Step 5

Fold each finger carefully along the lines to make three bendable joint sections.

Step 6

Cut each drinking straw into three short pieces and keep them sorted next to the folded fingers.

Step 7

Tape one straw piece over each joint on the back of every folded finger so the straw pieces line up to make a sliding tunnel.

Step 8

Cut a small rectangular pull tab from the extra cardboard.

Step 9

Tie one end of a piece of string to the tip of a folded finger with a small knot.

Step 10

Thread the string from the fingertip back through the straw tunnels toward the wrist so the string can slide.

Step 11

Tape the free end of the string to the cardboard pull tab so you can pull to move the tendon.

Step 12

Tape the base of each folded finger to the palm in the correct finger positions.

Step 13

Repeat Steps 9 to 11 for every finger so each finger has its own tendon and pull tab.

Step 14

Pull each pull tab to test curling and try picking up small objects; tighten knots or move tape if a finger needs adjustment.

Step 15

Share a photo or video of your finished robotic hand on DIY.org.

Final steps

You're almost there! Complete all the steps, bring your creation to life, post it, and conquer the challenge!

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Help!?

What can we use instead of drinking straws for the sliding tunnels if straws are hard to find?

If you don't have drinking straws (Step 5), substitute short rolled cardboard tubes from scrap paper or cut sections of a plastic pen casing to tape over the joints and create the same sliding tunnel for the string.

My string won't slide and the fingers won't curl—what should I check first?

If a finger won't curl, check that each straw piece is taped straight over the folded joint (Steps 5–6), that the string is threaded through every tunnel back to the wrist (Step 11), and re-seat or remove tape that is blocking the tunnel or tighten the knot at the fingertip (Step 10).

How can I adapt this activity for younger or older children?

For preschoolers have an adult pre-trace and cut the cardboard hand and straw pieces (Steps 1–5) and use wider straws, thicker string, and larger pull tabs, while older kids can add extra joint folds, use glue instead of tape for durability, or precisely measure segments for more realistic movement.

What are simple ways to enhance or personalize the finished robotic hand?

You can strengthen the palm by layering extra cardboard (Step 3), decorate and label each pull tab for different fingers (Step 12), or attach small servo motors to the pull tabs to make the tendons motorized for remote control.

Watch videos on how to build a robotic hand

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Build Your Own Bionic Hand - STEM Projects for Kids. Engineer A Simple Robot Hand

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Facts about basic robotics and simple machines

✋ There are two basic grips — power grips for holding tight and precision grips for pinching — try both to see what your robotic hand can pick up.

📦 Corrugated fiberboard (corrugated cardboard) is lightweight, cheap, and surprisingly strong — engineers use it for quick prototypes all the time.

🤖 Some advanced robotic hands (like the Shadow Hand) have 20–24+ degrees of freedom to mimic human motions.

🧵 Tendons (and strings in models) transmit pull efficiently with very little stretch, which is why string works great as 'muscles' in tendon-driven toys.

🖐️ The human hand has 27 bones and uses tendons like built-in cables to bend fingers.

How do I build a simple tendon-driven robotic hand?

Trace a child’s hand on cardboard and cut out two identical hand shapes. Cut fingers into strips or score fold-lines to make joints. Glue or tape the two layers together leaving a pocket for each finger so it bends. Tape short pieces of straw along each finger as a guide, then thread string through the straws and secure the end at the fingertip. Anchor strings at the wrist to a control stick; pull strings to curl fingers and test grasping.

What materials do I need to make a cardboard robotic hand?

You’ll need cardboard (cereal boxes work), scissors or a craft knife (adult use), drinking straws, strong string or twine, tape (duct or masking) and glue. Add a ruler, pencil, and a small stick or dowel to act as a control bar. Optional items: popsicle sticks or skewers for reinforcement, clothespins or binder clips, and markers to decorate. Keep small sharp tools away from young children and supervise cutting.

What ages is the tendon-driven robotic hand activity suitable for?

This activity suits ages about 6–14. Children 6–9 can build with adult help on cutting and threading; older kids (10–14) can design joints, experiment with lever lengths and multiple tendons independently. For preschoolers (age 4–5), provide pre-cut parts and focus on threading and pulling to see motion. Adjust complexity to match fine motor skills and provide supervision for any cutting or hot glue use.

What are the benefits of making a tendon-driven robotic hand?

Building a tendon-driven hand teaches basic engineering concepts—joints, levers, tension, and simple mechanics—while encouraging problem-solving, creativity, and fine motor skills. Testing different objects helps kids learn about grip types and material properties. It’s a low-cost way to introduce robotics principles, collaboration, and iteration: kids can redesign fingers or control mechanisms to improve performance and understand cause-and-effect through hands-on play.
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