Biodegradable TENG Humidity Response

ISEF Category: Energy: Sustainable Materials and Design

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

The Hook

A thin plastic film can act like a tiny power source, but the air around it can change the output a lot. That makes humidity a sneaky variable in triboelectric generators. If you want a project that feels real-world and measurable, this one has a lot going for it. You can test how a biodegradable film behaves as the room gets wetter and drier.

What Is It?

A triboelectric nanogenerator, or TENG, makes electricity when two materials touch and separate. Think of it like rubbing a balloon on your shirt, but in a more controlled device. One surface gives up electrons more easily, the other grabs them. That charge difference creates a measurable voltage or current.

In this project, you study films made from gelatin, corn starch, or a blend of both. These materials break down more easily than many plastics, so they interest researchers who want greener energy devices. Humidity matters because water in the air can let charge leak away faster. That means the same film can look strong in dry air and weak in damp air.

Why This Is a Good Topic

This topic works well because you can change one clear variable, humidity, and measure a real electrical response. You also get a direct link to a real problem, greener materials for wearable sensors and low-power devices. You can learn about materials choice, charge transfer, data collection, and control design without needing a full university lab. A strong version of this project can also compare film recipes, surface textures, or cycling patterns.

Research Questions

• How does relative humidity affect the peak voltage output of a gelatin film TENG?
• What is the effect of repeated humidity cycling on the stability of output from a corn-starch film TENG?
• Does a gelatin and corn-starch blend retain charge better than either material alone across humidity changes?
• To what extent does surface roughness change the humidity sensitivity of a biodegradable TENG?
• Which film composition gives the best output recovery after a dry-to-humid-to-dry cycle?
• How does exposure time to high humidity change the output decay rate of a biodegradable TENG?

Basic Materials

• Gelatin powder or sheets.
• Corn starch.
• Distilled water.
• Digital kitchen scale with 0.1 g accuracy.
• Measuring cups or graduated cylinders.
• Shallow trays or silicone molds for casting films.
• Nonstick drying surface or release liner.
• Desk fan or drying rack.
• Portable hygrometer and thermometer.
• Small hygrometer-controlled storage box or sealed container with desiccant and a damp sponge for humidity cycling.
• Copper tape or aluminum foil electrodes.
• Alligator clips and jumper wires.
• Multimeter with voltage and resistance settings.
• Ruler or calipers.
• Notebook or spreadsheet for data logging.

Advanced Materials

• Gelatin and corn starch for custom blends.
• Humidity chamber or sealed acrylic box with controlled inlet and outlet.
• Reference polymer films for comparison, such as PLA or cellulose acetate.
• Surface profilometer or optical microscope for texture checks.
• Electrometer or low-noise data acquisition system.
• Oscilloscope with high-input-impedance probe.
• Load resistors for output characterization.
• Sputtered or taped electrodes for consistent contact area.
• Analytical balance for film mass and moisture uptake.
• Environmental sensor for continuous humidity and temperature logging.

Software & Tools

• Google Sheets: Organizes trial data, calculates averages, and graphs humidity versus output.
• ImageJ: Measures film thickness, surface features, and visible texture changes from photos.
• Python: Fits trend lines, compares groups, and checks whether humidity cycling changes output recovery.
• Logger Pro: Records sensor data in real time if your school has compatible probes.
• NIH Image or ImageJ macros: Helps you batch-process repeated images for consistent measurements.

Experiment Steps

1. Define the exact film recipe, electrode layout, and output metric you will compare.
2. Choose one humidity pattern to test first, then decide how many cycles and repeats you need.
3. Build a measurement plan that keeps contact force, contact area, and motion as constant as possible.
4. Set up a calibration method so your electrical signal can be compared across trials and days.
5. Plan controls that separate humidity effects from film thickness, drying time, and surface texture.
6. Predefine how you will graph recovery, decay, and cycle-to-cycle change so your data answer the question directly.

Common Pitfalls

• Letting film thickness vary between casts, which makes humidity effects look larger or smaller than they really are.
• Changing contact pressure by hand, which can swamp the signal from the biodegradable film.
• Measuring output right after moving samples between dry and humid air, which mixes humidity effects with temperature and handling effects.
• Using a sensor setup with poor electrical shielding, which adds noise and hides small changes in output.
• Comparing films that dried unevenly, which creates hidden differences in moisture content before the test even starts.

What Makes This Competitive

A stronger project goes beyond a simple before-and-after test. You can compare multiple film blends, track recovery after repeated humidity cycles, and separate short-term charge loss from longer-term material change. Better entries also use a clear control film, repeated trials, and a careful statistical test instead of only reporting the biggest voltage. If you add surface measurements or moisture uptake data, you can explain why the output changes, not just show that it changes.

Project Variations

• Test gelatin-only, corn-starch-only, and blended films to see which one resists humidity best.
• Compare smooth films with roughened films to see whether surface texture changes charge loss in damp air.
• Measure output recovery after different humidity cycle patterns, such as short cycles versus long cycles, to study reversibility.

Learn More

• PubMed: Search review articles on triboelectric nanogenerators, humidity effects, and biodegradable polymers to find background and methods.
• NASA Earthdata: Explore humidity and atmospheric water vapor data for context on why ambient moisture matters in outdoor devices.
• NIH PubChem: Look up basic properties of gelatin-related and starch-related compounds, then connect chemistry to material behavior.
• MIT OpenCourseWare: Search materials science and energy harvesting lecture notes for fundamentals on surface charge and dielectric behavior.
• Journal of Materials Chemistry A: Search recent papers on biodegradable triboelectric devices and compare testing methods.