Yeast Adhesion on Microtextured Polymer Surfaces

ISEF Category: Biomedical Engineering

Subcategory: Cell and Tissue Engineering  ·  Difficulty: Intermediate  ·  Setup: School Lab  ·  Time: 1 to 2 Months

The Hook

A surface can act like Velcro for cells, or like ice. Tiny grooves, pits, and ridges can change how much a cell sticks. That matters in implants, wound dressings, and tissue scaffolds. You can model that effect with grocery-store yeast and simple imaging.

What Is It?

This project asks how surface texture changes cell sticking. In tissue engineering, scientists care about cell adhesion because cells need to attach before they can grow, spread, and make tissue. Your stand-in is yeast, a single-celled organism that is easy to grow and image. Yeast is not a mammalian cell, but it gives you a low-cost way to compare how different surfaces attract or repel cells.

Think of the surface like a parking lot. A smooth lot gives cells one kind of experience, while grooves and rough patches give them another. PLA, PCL, and silk each have different chemistry and structure, so they may hold cells differently even before you add texture. By comparing microtextures, you can test whether small physical features change adhesion in a measurable way.

Why This Is a Good Topic

This is a strong science fair topic because you can change one clear variable, the surface texture, and measure one clear outcome, cell coverage or density. It connects to real biomaterials work, since engineers design implant and scaffold surfaces to control cell attachment. You can do real analysis with basic imaging, statistics, and careful controls, even if you do not have prior lab experience.

Research Questions

• How does microtexture depth affect yeast adhesion on PLA surfaces?
• How does ridge spacing affect yeast adhesion on PCL surfaces?
• Does silk show a different adhesion pattern from PLA and PCL at the same texture level?
• To what extent does surface roughness change the percentage of area covered by yeast cells?
• Which texture pattern produces the highest yeast density on each polymer type?
• How does adhesion change when you compare textured surfaces with smooth control surfaces?

Basic Materials

• PLA sheets or 3D-printed PLA coupons.
• PCL film or pellets formed into flat coupons.
• Silk fabric or silk-based film coupons.
• Hobby diode laser or access to a school makerspace laser.
• Smartphone microscope attachment.
• Smartphone with manual exposure control.
• Grocery-store baker's yeast.
• Distilled water.
• Small clear containers or Petri dishes.
• Digital kitchen scale with 0.1 g accuracy.
• Ruler or digital caliper.
• Nitrile gloves.
• Permanent marker for labeling samples.
• Image analysis reference grid or printed calibration slide.

Advanced Materials

• Universal testing or surface characterization access, if available.
• Contact angle goniometer.
• Optical profilometer or confocal microscope.
• Scanning electron microscope access for surface confirmation.
• Fluorescence microscope and safe cell stain, if your lab allows it.
• Incubator for controlled adhesion timing.
• Sterile Petri dishes and microbiology supplies.
• Analytical balance.
• Image capture stand with fixed geometry.
• Reference standards for densitometry calibration.

Software & Tools

• ImageJ: Measures cell coverage, grayscale intensity, and texture features from microscope images.
• Python: Automates image thresholding, batch measurements, and statistical plots.
• Google Sheets: Organizes samples, replicates, and summary statistics.
• R: Runs stronger statistical tests and makes publication-style figures.
• NIH ImageJ macro recorder: Helps you repeat the same image analysis steps across all samples.

Experiment Steps

1. Define one texture variable to change first, such as groove spacing, groove depth, or surface roughness.
2. Choose your control surfaces and match them for material, size, and cleaning method.
3. Plan a repeatable way to make each texture pattern and verify that the pattern really changed.
4. Design your adhesion measurement so the same imaging settings and counting rules apply to every sample.
5. Build a calibration plan for turning smartphone images into a numeric adhesion score.
6. Decide which statistics will compare materials, textures, and replicate-to-replicate variation.

Common Pitfalls

• Mixing up surface chemistry and surface texture, which makes it hard to tell what caused any adhesion change.
• Letting laser settings drift between samples, which creates uneven texture patterns that do not match your design.
• Photographing samples under changing room light, which makes densitometry values shift between sessions.
• Counting clumped yeast as separate cells, which inflates adhesion numbers on rough surfaces.
• Comparing different polymer samples with different cleaning or drying history, which changes stickiness before you even test adhesion.

What Makes This Competitive

A class-level version of this project just compares a few textures and reports which one looks stickier. A stronger entry controls the chemistry of the polymers, verifies the texture with real measurements, and uses more than one analysis method, such as coverage, cluster size, and spatial distribution. You can also compare your yeast results with published mammalian-cell trends to ask whether the same surface features predict adhesion across cell types. That kind of cross-system comparison makes the project feel more like biomaterials research.

Project Variations

• Test how adhesion changes on only one polymer, then vary the laser texture pattern to isolate geometry effects.
• Compare textured PLA with textured silk in the same assay to ask whether chemistry or roughness matters more.
• Add a post-treatment step, such as coating the surface with a thin protein layer, and measure how that changes yeast attachment.

Learn More

• NIH PubMed: Search for review articles on cell adhesion, surface roughness, and biomaterials to compare your results with published work.
• NCBI Bookshelf: Read free textbook chapters on cell membranes, extracellular matrix, and biomaterials basics.
• MIT OpenCourseWare: Look for materials science or biomedical engineering lecture notes on surface properties and tissue engineering.
• USDA Forest Products Laboratory: Find free reports on cellulose, fibers, and surface characterization methods that help with texture thinking.
• ImageJ Documentation: Use the official user guides and tutorials on the ImageJ website to learn measurement and thresholding.