TENG Shoe Insoles and Step Frequency

ISEF Category: Energy: Sustainable Materials and Design

Subcategory: Triboelectricity and Electrolysis  ·  Difficulty: Intermediate  ·  Setup: Home Setup  ·  Time: 1 to 2 Months

The Hook

Every step can make a tiny charge. That makes your shoe more than footwear, it becomes a moving energy source. If you can measure that signal well, you can turn walking into a real engineering project. The trick is proving when the power goes up, and when it does not.

What Is It?

A triboelectric nanogenerator, or TENG, makes electricity when two materials touch and separate. In this project, PTFE tape and aluminum foil act like a tiny charge-making pair. When pressure from a step changes their contact, electrons move. That creates a measurable electrical signal.

Think of it like rubbing a balloon on your hair, except the rubbing comes from your foot motion inside a shoe insole. PTFE tends to gain electrons, and aluminum tends to lose them. Each step changes the contact area and force, so the output can change with how fast and how hard you walk. That gives you a clean way to test a real engineering question: does stepping faster always mean more harvested energy, or does the signal peak at a certain walking pattern?

The phone IMU, short for inertial measurement unit, records motion data from the phone’s accelerometer and gyroscope. That lets you connect the electrical output to a walking pattern instead of guessing from step count alone. You can compare step frequency, stride regularity, and acceleration spikes to the TENG signal.

Why This Is a Good Topic

This is a strong science fair topic because you can measure a clear cause and effect. You change walking pattern, then track electrical output and motion data. That gives you real data, not just a cool demo. The project connects to wearable energy harvesting, smart footwear, and low-power sensors. You can also learn how to build controls, collect repeated trials, and analyze time-series data.

Research Questions

• How does step frequency change the peak voltage produced by a PTFE-aluminum insole TENG? ?
• What is the effect of walking speed on the average power output of the insole TENG? ?
• Does adding phone IMU data improve the prediction of TENG output compared with using step count alone? ?
• To what extent does stride regularity affect the consistency of the TENG signal? ?
• Which walking pattern, slow walk, normal walk, or fast walk, produces the highest energy per step? ?
• How does the output of a single-layer insole compare with a two-layer insole design under the same walking pattern? ?

Basic Materials

• PTFE tape or PTFE sheet.
• Aluminum foil or thin aluminum tape.
• Flexible insulating backing material for the insole base.
• Adhesive tape or contact cement suitable for craft materials.
• Wires with alligator clips.
• Multimeter or USB data logger for voltage readings.
• Smartphone with an accelerometer and gyroscope app.
• Measuring tape or marked walking path.
• Notebook or spreadsheet for trial logging.

Advanced Materials

• Oscilloscope with data export.
• Low-noise data acquisition system.
• Precision force sensor or load cell.
• Flexible substrate materials for repeated-bend testing.
• Conductive fabric or copper tape for improved contacts.
• 3D-printed insole housing or laser-cut template.
• Reference resistor set for power calculations.
• Environmental meter for temperature and humidity tracking.

Software & Tools

• Excel or Google Sheets: Organizes trial data, makes graphs, and compares output across walking conditions.
• Python: Fits models, processes IMU time series, and checks whether step frequency predicts voltage or power.
• Logger Pro: Records motion or sensor data if your school has access to it.
• ImageJ: Measures contact area changes if you photograph the insole layers during design tests.
• PubMed: Helps you find review articles on triboelectric nanogenerators and wearable energy harvesting.

Experiment Steps

1. Define the exact walking variable you will change first, such as step frequency, stride length, or pace category.
2. Design a repeatable insole geometry so every trial uses the same PTFE and aluminum contact pattern.
3. Plan a measurement setup that captures both electrical output and phone IMU motion data at the same time.
4. Build controls that separate step count effects from walking style effects, such as keeping route and footwear constant.
5. Decide how you will convert voltage traces into comparable metrics like peak voltage, average power, or energy per step.
6. Preplan your statistics so you can test whether differences across walking conditions are larger than trial-to-trial noise.

Common Pitfalls

• Letting the PTFE and aluminum layers shift inside the shoe, which changes contact area from trial to trial.
• Recording phone IMU data with the phone in a different pocket or position, which breaks comparison across walks.
• Mixing up peak voltage and average power, which makes the energy result hard to interpret.
• Using only one walking trial per condition, which hides how variable human steps really are.
• Ignoring humidity and sweat, which can weaken triboelectric charge transfer and flatten the signal.

What Makes This Competitive

A stronger version of this project goes beyond a simple demo of shoe-generated electricity. You need repeated trials, a clear control design, and a clean way to tie motion data to output. A competitive entry often tests more than one insole layout, then uses statistical analysis to show which design works best. If you can model how step frequency and gait features predict output, your project starts to look like real wearable-sensor research.

Project Variations

• Compare barefoot, sneaker, and boot conditions to see how shoe material changes TENG output.
• Test whether left foot and right foot insoles produce different signals during the same walking route.
• Use a phone app that records gait symmetry or cadence, then compare those features with harvested energy.

Learn More

• MIT OpenCourseWare: Search for materials science, sensors, and energy harvesting lecture notes that explain contact electrification and signal analysis.
• NASA NTRS: Search the NASA Technical Reports Server for wearable energy harvesting and triboelectric generator papers.
• PubMed: Search review articles on triboelectric nanogenerators, wearable sensors, and biomechanical energy harvesting.
• NIH 3D Print Exchange: Use this if you want ideas for flexible wearable housings and prototypes.
• Google Scholar: Search for recent peer-reviewed papers on PTFE-aluminum triboelectric generators and insole harvesters.