Acrylic Microtexturing And Biofilm Reduction

ISEF Category: Microbiology

Subcategory: Other  ·  Difficulty: Advanced  ·  Setup: University Lab  ·  Time: Full Year

The Hook

Some surfaces make bacteria stick like glue, while others seem to make them slip away. That difference can start with tiny grooves you cannot see by eye. If you can link surface shape to biofilm growth, you can turn a cheap sheet of acrylic into a real research question. That is a strong science fair angle.

What Is It?

This project asks whether tiny laser-engraved textures on acrylic change how much B. subtilis can build a biofilm on the surface. A biofilm is a slimy layer of microbes that attach to a surface and surround themselves with their own protective matrix. Think of it like bacteria building a tiny neighborhood instead of living as single free-floating cells.

The physics idea behind the project comes from wetting theory. The Cassie-Baxter model describes how a liquid sits on a rough surface when air stays trapped in the texture. If a surface holds less liquid contact, microbes may have a harder time landing, spreading, or staying attached. Your job is to test whether a specific texture pitch, the spacing between features, actually changes biofilm coverage in a repeatable way.

Why This Is a Good Topic

This is a good science fair topic because you can vary one design feature, measure a clear outcome, and compare real patterns against a theory-based prediction. It connects microbiology, surface design, and materials science in a way that feels modern and practical. You can learn how to plan controls, quantify images, and use statistics to decide whether a pattern matters or not.

Research Questions

• How does feature pitch on laser-engraved acrylic affect B. subtilis biofilm coverage?
• What is the effect of surface texture depth on B. subtilis attachment after incubation?
• Does a Cassie-Baxter-like texture reduce biofilm coverage more than a smooth acrylic control?
• To what extent does repeated cleaning change the anti-biofilm effect of the engraved surface?
• Which texture pattern, grid, line, or dot array, produces the lowest biofilm coverage?
• How does the measured wetting angle relate to final biofilm area on each acrylic pattern?

Basic Materials

• Handheld laser engraver capable of engraving acrylic
• Clear acrylic sheets of the same thickness
• Pre-cut acrylic coupons of equal size
• Fine-point permanent marker for labeling samples
• Digital caliper for measuring feature spacing
• Contact angle setup or smartphone-based droplet imaging kit
• Sterile Petri dishes
• B. subtilis culture from an approved lab source
• Appropriate growth medium and agar plates
• Micropipettes and sterile tips
• Sterile cotton swabs or spreaders
• Incubator with temperature control
• Disposable gloves, lab coat, and eye protection
• Metric ruler
• Smartphone or digital camera with fixed tripod mount
• ImageJ for measuring covered area from photos

Advanced Materials

• Profilometer or optical microscope for checking texture geometry
• Confocal microscope or fluorescence microscope for biofilm imaging
• Fluorescent stain approved for biofilm visualization
• Surface energy measurement setup
• Atomic force microscope for surface roughness if available
• Analytical balance for sample mass checks
• Spectrophotometer for inoculum standardization
• Autoclave for sterilizing materials
• Environmental chamber for controlled humidity tests
• Higher-resolution camera with macro lens for surface imaging
• Statistical software with mixed-effects modeling support

Software & Tools

• ImageJ: Measures biofilm coverage from images and helps you turn surface photos into area data.
• RStudio: Runs statistics, makes graphs, and helps compare texture groups fairly.
• Google Sheets: Organizes sample IDs, measurements, and cleaning logs in one place.
• Plotly Chart Studio: Builds clean visualizations of coverage, angle, and texture data.
• Python: Automates image processing if you want to segment colonies or compare many samples.

Experiment Steps

1. Define the exact texture variables you will test, such as pitch, pattern type, and depth, and keep every other surface feature as similar as possible.
2. Choose one biofilm measurement method, then plan how you will convert each sample into a numeric coverage score.
3. Build a control set with smooth acrylic and at least one texture pattern that should act as a weak or neutral comparator.
4. Decide how you will measure wetting behavior on the same samples so you can compare surface physics with biofilm outcome.
5. Plan replication and randomization so each texture is tested on multiple samples and in more than one run.
6. Map out your analysis before collecting data, including how you will handle outliers, compare groups, and test whether the texture effect matches the theory prediction.

Common Pitfalls

• Using engraved samples with different cleaning quality, which leaves residue that changes bacterial attachment.
• Letting texture depth vary from sample to sample, which makes pitch and roughness impossible to separate.
• Measuring biofilm from uneven photos, which creates false differences in coverage between groups.
• Skipping wetting measurements, which leaves the Cassie-Baxter claim untested.
• Using too few replicates, which makes a real texture effect look random or hides a weak but real trend.

What Makes This Competitive

A stronger project would not stop at smooth versus textured. It would test several pitches, quantify surface geometry carefully, and compare the biofilm result with a wetting measurement on the same material. You can also raise the level by using blinded image scoring, stronger statistics, and a second microbe or a second pattern type as a comparison. That turns a simple surface test into a real structure-function study.

Project Variations

• Test whether the same texture patterns affect a different surface bacterium, such as a nonpathogenic lab strain used in teaching labs.
• Compare laser-engraved acrylic with another cheap material, such as polystyrene or polycarbonate, to see whether material chemistry changes the result.
• Add a wettability angle analysis and ask whether contact angle predicts biofilm coverage better than roughness alone.

Learn More

• PubMed: Search review articles on biofilms, surface roughness, and microbial attachment to find background and methods.
• NIH NCBI Bookshelf: Look for free textbook chapters on biofilms, bacterial adhesion, and microbial growth.
• NASA NTRS: Search for papers on surface texturing, wettability, and Cassie-Baxter behavior on engineered materials.
• MIT OpenCourseWare: Find free materials on surface science, materials engineering, and experimental design.
• ImageJ Documentation: Read the official guides for measuring area, thresholding images, and batch analysis.