Mycelium Battery Separators and Ionic Conductivity

ISEF Category: Energy: Sustainable Materials and Design

Subcategory: Biological Process and Design  ·  Difficulty: Intermediate  ·  Setup: School Lab  ·  Time: 1 to 2 Months

The Hook

Most batteries depend on a thin separator that keeps the electrodes apart while ions still move through. That part matters more than most people think. If you can make that separator from mycelium, you are looking at a material that grows itself and can break down later. That mix of biology and energy storage makes for a smart science fair project.

What Is It?

Mycelium is the root-like network of fungi. Oyster mushroom substrate grows fast and forms a tangled web of tiny threads called hyphae. In this project, you are asking whether that living or dried network can act like a battery separator, which is the layer that prevents a short circuit while still letting charged particles, called ions, move through.

Think of the separator like a bouncer at a crowded door. It blocks the two battery sides from mixing, but it still lets the right people through. Your job is to see whether mycelium changes that balance as it grows. A younger mat may be thinner and wetter. A more mature mat may be denser, more uniform, or harder to pass through. Those changes can affect ionic conductivity, which is how easily ions move through the material.

Why This Is a Good Topic

This is a strong science fair topic because you can test a real material property, compare samples by growth stage, and connect your work to cleaner battery design. You are not just growing fungus for fun. You are measuring whether biology can solve an engineering problem. You can learn sample preparation, conductivity testing, graphing, and how to control a material that changes over time.

Research Questions

• How does mycelium growth time affect ionic conductivity in a separator sample?
• What is the effect of drying versus keeping the mycelium sample hydrated on ionic conductivity?
• Does mycelium thickness change the separator's resistance to ion flow?
• To what extent does pressing or compressing the mycelium mat change conductivity?
• Which growth stage gives the best balance between ionic conductivity and short-circuit prevention?
• How does the substrate composition affect the conductivity of the finished mycelium separator?
• Does adding a salt solution during testing change the conductivity trend across growth stages?

Basic Materials

• Oyster mushroom mycelium or spawn on a safe growth substrate.
• Sterile petri dishes or shallow food-safe containers.
• Digital kitchen scale with 0.1 g accuracy.
• Ruler or digital caliper.
• Distilled water.
• Table salt or another safe electrolyte for simple conductivity testing.
• Multimeter with resistance mode.
• Graph paper or spreadsheet software.
• Nitrile gloves.
• Masking tape and labels.
• Paper towels.
• Plastic wrap or loose lids to reduce contamination.

Advanced Materials

• Oyster mushroom mycelium starter culture.
• Controlled growth containers with ventilation filters.
• Analytical balance.
• Calipers or thickness gauge.
• LCR meter or impedance analyzer.
• Two-electrode or four-electrode conductivity cell.
• Reference separator material for comparison.
• Humidity and temperature probe.
• Drying oven or desiccator.
• Microscope or stereo microscope.
• ImageJ for pore and structure analysis.
• Electrochemical workstation for impedance spectroscopy.

Software & Tools

• Google Sheets: Organizes measurements, calculates averages, and makes graphs of conductivity versus growth time.
• ImageJ: Measures sample thickness, pore size, and surface coverage from photos or microscope images.
• Python: Fits trends, compares groups, and helps you run cleaner statistics on repeated trials.
• R: Runs statistical tests and plots when you want more control over the analysis.
• BioRender: Helps you sketch a clear diagram of the separator, cell setup, and measurement path.

Experiment Steps

1. Define the exact property you will measure, then decide whether you are testing bulk ionic conductivity, resistance, or a battery separator proxy.
2. Choose one growth variable to change first, such as growth time, while holding substrate, moisture, and sample shape as steady as possible.
3. Plan how you will measure structure and performance from the same sample set, so you can connect texture, thickness, and conductivity.
4. Build a calibration or comparison method that lets you turn instrument readings into a meaningful material property.
5. Design controls that separate true mycelium effects from simple moisture or thickness effects.
6. Map out your analysis plan before collecting data, including repeats, error bars, and the statistical test you will use.

Common Pitfalls

• Measuring wet and dry samples together, which makes moisture the real variable instead of growth time.
• Using samples with different thicknesses, which confuses conductivity changes with simple distance effects.
• Letting contamination or uneven growth create patchy mats, which makes one sample unlike the next.
• Reading resistance with poor electrode contact, which adds contact error that hides the material signal.
• Skipping a control separator, which leaves you unable to tell whether mycelium actually performs better than a standard material.

What Makes This Competitive

A strong version of this project does more than compare two growth stages. It separates growth time from moisture, thickness, and structure, then uses those controls to explain why conductivity changes. You can raise the quality again by pairing electrical data with imaging or pore analysis. If you also compare mycelium to a standard separator material, your results get much more useful.

Project Variations

• Test whether oyster mushroom mycelium from different substrates, such as sawdust versus cardboard, changes conductivity and structure.
• Compare dried mycelium sheets with lightly hydrated sheets to see how water content affects ion transport.
• Analyze whether compression during drying changes pore size and separator performance more than growth time does.

Learn More

• NIH PubMed: Search for review articles on fungal materials, biomaterials, and bio-based separators to find current methods and terminology.
• NASA Tech Reports Server: Search for lightweight materials, porous structures, and bio-inspired composites that may inform your design.
• USGS Water Science School: Review how ions move in water and porous media, which helps with the transport side of this project.
• MIT OpenCourseWare: Search materials science and electrochemistry course notes for free explanations of conductivity, resistance, and diffusion.
• Journal of Power Sources: Search the journal for papers on biodegradable separators, mycelium composites, and battery materials.