Kombucha Biofilm Oil Penetration Kinetics Project

ISEF Category: Translational Medical Science

Subcategory: Drug Identification and Testing  ·  Difficulty: Intermediate  ·  Setup: Home Setup  ·  Time: 1 to 2 Months

The Hook

A thin biofilm can act like a tiny wall. If an oil cannot move through it, the signal stops there. That makes kombucha-SCOBY films a cheap way to study how soft materials block or absorb compounds. You can turn a kitchen byproduct into a real transport experiment.

What Is It?

This project looks at how fast an essential-oil emulsion moves into a SCOBY, which is the rubbery biofilm used to make kombucha. A biofilm is a living or once-living layer of cells and polymers, basically a sticky mesh. You are not testing a medicine on people. You are using the SCOBY as a model surface that can stand in for a soft biological barrier.

Think of the SCOBY like a sponge with a skin on top. Some liquids bead up, some spread, and some soak in. By filming the sample over time and measuring thickness or color change in ImageJ, you can turn that movement into numbers. That gives you a way to compare different emulsions, oils, or surface treatments.

Why This Is a Good Topic

This is a strong science fair topic because you can change one variable at a time and measure a clear outcome. The setup is low-cost, but the question connects to real problems in drug delivery, wound care, and antimicrobial surfaces. You can learn image analysis, kinetics, experimental controls, and basic statistics without needing a university lab.

Research Questions

• How does essential-oil concentration affect penetration depth in a SCOBY biofilm?
• What is the effect of emulsifier type on oil spread rate through the biofilm?
• Does oil droplet size change how quickly the emulsion enters the SCOBY surface?
• To what extent does biofilm thickness change measured penetration kinetics?
• Which essential oil shows the fastest visible penetration through a kombucha-SCOBY film?
• How does pH of the emulsion affect the amount of absorbance or thickness change in the biofilm?

Basic Materials

• Kombucha SCOBY films of similar size and age.
• Essential oils from a single source, such as tea tree, eucalyptus, or peppermint.
• Food-grade emulsifier, such as lecithin or polysorbate if allowed by your school.
• Distilled water.
• Clear glass slides or Petri dishes.
• Smartphone with a manual camera app.
• Clip-on smartphone microscope or low-cost USB microscope.
• Metric ruler or printed calibration slide.
• ImageJ installed on a computer.
• Digital kitchen scale with 0.1 g accuracy.
• Disposable pipettes or transfer pipettes.
• Nitrile gloves and safety goggles.

Advanced Materials

• Analytical balance.
• Stereo microscope with a camera attachment.
• Controlled light box for repeatable imaging.
• Rheometer or viscometer for emulsion properties.
• Zeta potential instrument for droplet stability.
• Particle size analyzer or microscope-based droplet measurement setup.
• pH meter.
• Incubator or temperature-controlled chamber.
• Tensile tester for biofilm mechanical properties.
• Desiccator for standardized sample conditioning.
• Software for statistical analysis and graphing.

Software & Tools

• ImageJ: Measures thickness, area, and intensity changes in each frame of your time-lapse images.
• Google Sheets: Organizes measurements and helps you make graphs and summary statistics.
• LibreOffice Calc: Gives you a free spreadsheet option for data entry and plotting.
• Python: Helps you fit curves, compare groups, and automate image measurements if you want more advanced analysis.
• Tracker: Lets you inspect time-based changes frame by frame and verify your image timing.

Experiment Steps

1. Define one clear transport question, such as how oil type, emulsifier type, or biofilm thickness changes penetration rate.
2. Standardize the SCOBY samples so each film starts with similar size, age, moisture, and visible texture.
3. Choose a measurement method, such as edge movement, color change, or thickness change, and decide how ImageJ will capture it.
4. Plan controls that separate true penetration from simple surface wetting, evaporation, and lighting changes.
5. Build a calibration system so you can convert image features into a consistent numeric scale across trials.
6. Decide how you will compare groups, including repeats, summary statistics, and a test for whether the differences are larger than noise.

Common Pitfalls

• Using SCOBY films with different ages or thicknesses, which makes penetration look different even when the emulsion is the same.
• Changing the phone angle or room light between frames, which shifts the apparent boundary in your time-lapse.
• Treating surface wetting as penetration, which overstates how far the oil actually moved into the biofilm.
• Mixing emulsions inconsistently, which changes droplet size and stability from trial to trial.
• Measuring on the most translucent part of the SCOBY every time, which biases the result because the film is not uniform.

What Makes This Competitive

A competitive version of this project goes past a simple before-and-after comparison. You would quantify a real transport rate, compare at least two mechanisms, and show that your controls rule out lighting, thickness, and wetting artifacts. Strong projects also link image data to a second measurement, such as droplet size or biofilm structure, so the result has more than one layer of evidence. Careful statistics and repeatability matter a lot here.

Project Variations

• Test different essential oils, such as tea tree, peppermint, and eucalyptus, to see whether chemical composition changes penetration behavior.
• Compare SCOBY films with agar gels or gelatin sheets to see whether the biofilm structure changes transport.
• Measure how emulsifier choice changes both visible spread and droplet stability before the oil reaches the biofilm.

Learn More

• ImageJ documentation: Learn how to measure distance, area, and intensity in time-lapse images, then search for the official ImageJ help pages.
• PubMed: Search review articles on biofilms, essential oils, and emulsion transport to build your background section.
• NIH PubMed Central: Read free full-text papers on topical delivery, biofilms, and soft-matter diffusion.
• NOAA educational resources: Review basic diffusion, mixing, and experimental measurement concepts with accessible science explanations.
• MIT OpenCourseWare: Look for free materials on transport phenomena, fluid basics, and data analysis methods.
• USDA food science resources: Find background on emulsions, fats, and food-grade surfactants through USDA publications and fact sheets.