Keywords

Biofilms, permeability, soft matter physics, cryosuction microscopy, microscopy

Description
Biofilms are dense microbial communities embedded in a self-produced polymeric matrix that behave as hydrated soft materials. They are ubiquitous in natural and engineered environments and play key roles in processes ranging from water filtration and environmental remediation to infection and antibiotic resistance. A central property governing biofilm function is permeability—the ability of fluids and solutes to move through the biofilm matrix. Permeability determines how nutrients reach microbial cells, how contaminants are retained or filtered in water treatment systems, and how drugs or antibiotics penetrate biofilm-associated infections. Despite its importance, measuring permeability and compressibility in biofilms at small scales remains challenging.

In the Isa Group (D-MATL), a microscopy-based technique has recently been developed to measure compressibility and permeability in hydrogel microparticles. The method uses a temperature-controlled freezing stage mounted on a standard optical microscope. When the temperature is lowered, ice nucleates in the sample and induces cryosuction, a thermodynamic process that draws water out of hydrated materials. As water is extracted, hydrogel particles shrink and their volume change can be quantified by microscopy. Because cryosuction pressure is directly related to temperature, this approach enables the construction of pressure–volume curves from which the bulk modulus can be determined. By imposing a temperature gradient, the same platform can also probe permeability: cryosuction-driven water flow generates directional particle motion that can be tracked by time-lapse microscopy and related to the pressure gradient using Darcy’s law.

In this project, a collaboration between Eleonora Secchi (D-BAUG) and Robert Styles (D-MATL), we aim to adapt this cryosuction-based microscopy technique, originally developed for synthetic hydrogels, to study biofilms.

Skills you will learn

• Adaptation and operation of a cryosuction-based microscopy experimental platform
• Microbiology techniques related to biofilm culture and handling
• Microscopy (bright-field and fluorescence imaging)
• Image analysis and data processing (Python)

Goal

The goal of this project is to adapt a cryosuction-based microscopy platform to measure compressibility and permeability in biofilms. The student will adapt the experimental setup to biological samples and quantify how biofilm structure and composition influence fluid transport by measuring pressure–volume responses and permeability using microscopy and image analysis. The project lies at the interface of microbiology, soft matter physics, and environmental engineering and will contribute to a better understanding of transport processes in microbial materials.

Project start

Anytime

Related Image

Location

Department of Materials, Vladimir-Prelog-Weg 1-5 / 10, 8093 Zürich (Switzerland)

Project type

This project can be adapted for Master Thesis or Master Project.

Contact details

Eleonora Secchi (D-BAUG): esecchi@ethz.ch; Robert Styles (D-MATL): robert.style@mat.ethz.ch