Control a Claw Neuroprosthetic

Use the electrical signals in your forearm to command a robotic gripper. You’ll place EMG electrodes, stream muscle activity to The Claw, and stack cups into a tower—an eye-opening intro to modern neuroprosthetics.

Devices and Accessories3

About the Experiment

What Will You Learn?

How to place neuromuscular electrodes and record EMG.
Core ideas behind brain–machine interfaces and neuroprosthetics.
Fine-motor control using real-time muscle feedback.
Hands-on robotic control driven entirely by EMG signals.

Background

Brain-machine interfaces translate natural bioelectric signals into movement commands for external devices. Prosthetic hands, for example, interpret residual muscle activity so users can grasp objects. In this challenge, your own forearm EMG will drive The Claw as you stack cups—showcasing how biology and engineering team up to restore dexterity.

Procedure

Setup & First Test
Materials:
- The Claw with 9 V battery
- Orange electrode cable (plugs straight into The Claw, which has its own muscle amplifier)
- Three disposable EMG electrodes
- Six lightweight plastic cups
Steps:
1. Electrode placement—Apply two electrodes over your forearm flexor muscle and one on the back of your hand (ground). Clip the two red leads to the forearm electrodes and the black lead to ground.
2. Power up—Insert a fresh battery, press the power button, then tap the mode button to set the pincer’s start position (open/closed).
3. Test grip—Flex and relax to open/close The Claw. Adjust electrode positions until movement is smooth.
4. Cup setup—Place six cups upside-down at the edge of your workspace; you’ll build a 3-2-1 pyramid in the center using only The Claw.

Gameplay & Rules

Cup Stacking
A) Stack the cups • Do not reset the start position once play begins. • If you knock cups over, pick them up only with The Claw. • A cup that rolls out of reach ends the round. • Build the 3-2-1 pyramid as fast as possible.
B) Dismantle the pyramid • Return cups to their original stack—again using only The Claw. • Race friends or try to beat your own best time.
C) Variations • Move cups farther away or change angles. • Try controlling The Claw with a different muscle (biceps vs. forearm). • Introduce obstacles or heavier objects for an extra challenge.

Results & Insights

Data to collect • Time to build and dismantle the pyramid. • Grip stability vs. flex strength. • Muscle fatigue across repeated rounds.

Troubleshooting tips • Weak or jittery motion? Check battery level and secure electrodes. • Claw drifts on its own? Verify cable orientation and avoid electrical noise. • LEDs on but no movement? Press the mode button or power-cycle.

These same principles underlie clinical BMIs that restore movement to people with limb loss or paralysis—your cup-stacking race uses the very tech driving tomorrow’s neuroprosthetics.

Model it • Draw the pathway from your motor cortex through your spinal cord to your forearm flexor muscle and on to The Claw, and label where your electrodes picked up the signal.

Design Challenge

Where Should the Electrodes Go?
Prosthetic hands read muscle signals through electrodes on the skin, and where those electrodes sit decides whether the hand grips when its user means it to, and only then. Can your team find the placement that works best?
1. Write down your criteria and rank them: The Claw responds to every flex, it never moves while your arm is relaxed (no false triggers), and the electrodes are comfortable to wear.
2. Test at least three placements of the two red-lead electrodes on your forearm (for example close together over the flexor muscle, farther apart, or nearer the wrist), keeping the ground on the back of your hand. For each, count how many of 10 flexes move The Claw and how many times it moves during 30 seconds of rest, then time one pyramid build.
3. Record your results in a table, combine the best features into one final placement, and test it again.
4. Explain your trade-offs: did the placement that gripped most reliably also feel comfortable and give your best time?
5. Judge your final placement for someone who uses a prosthetic hand every day: what would it cost, is it safe and comfortable to wear all day, and who could or could not use it?

NGSS alignment

Performance expectations

MS-LS1-3 Use argument supported by evidence for how the body is a system of interacting subsystems composed of groups of cells.

Your nervous system and forearm muscle work together, and a machine reads the result.
HS-LS1-2 Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.

Draw the pathway from motor cortex to forearm flexor and on to The Claw: brain, nerve and muscle as one system, extended by a machine.
MS-ETS1-2 Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.

Score at least three electrode placements against ranked criteria in one table (design challenge).
MS-ETS1-3 Analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success.

Compare at least three placements in a table, combine the best features into one final placement and test it again (design challenge).
HS-ETS1-3 Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, and aesthetics, as well as possible social, cultural, and environmental impacts.

Rank reliability, no false triggers and comfort, explain the trade-offs, and judge the final placement for an everyday prosthetic user (design challenge).

Science and engineering practices

1 Asking Questions and Defining Problems

Define the problem: write and rank criteria for a reliable, comfortable grip before testing (design challenge).
2 Developing and Using Models

Draw the pathway from your motor cortex to your forearm flexor and on to The Claw, and label where your electrodes picked up the signal.
3 Planning and Carrying Out Investigations

Run timed cup-stacking rounds controlled only by EMG, then test at least three electrode placements.
4 Analyzing and Interpreting Data

Count grips and false triggers for each placement and compare them with your times and comfort.
6 Constructing Explanations and Designing Solutions

Design a final placement from the test data, retest it, and explain the trade-offs (design challenge).

Crosscutting concepts

Cause and Effect

Flexing opens and closes the claw.
Influence of Science, Engineering, and Technology on Society and the Natural World Engineering connection

The same principles restore movement to people with limb loss or paralysis.

Disciplinary core ideas

LS1.D Information Processing

The device reads the muscle activity that motor commands produce.
LS1.A Structure and Function

Nerve and muscle are specialized tissues that work together to make the signal.
ETS1.B Developing Possible Solutions

Test several placements against ranked criteria in one table.
ETS1.C Optimizing the Design Solution

Combine the best features of the tested placements and retest.