PhD Candidate in Biophysics and Rheology of Bacterial Biofilms / PhD Candidate in Biophysics and Rheology of Bacterial Biofilms

Two PhD Positions in Biophysics and Rheology of Bacterial Biofilms

100%, Zurich, fixed-term

The bioMatter Microfluidics Group of Dr. Eleonora Secchi at ETH Zurich is seeking two PhD candidates. Our research focuses on uncovering the physicochemical mechanisms that control microbial surface colonization and biofilm assembly, structure, and rheology. We employ a diverse array of technologies from materials science, microbiology, and microfluidics, as well as advanced imaging techniques to address our research questions. We are a highly interdisciplinary, international, and collaborative team of approximately 10 members, hosted within the chair of Prof. Roman Stocker in the Institute of Environmental Engineering.

Project Background

The two PhD positions are part of a recently funded SNSF project aimed at systematically investigating nonlinear biofilm rheology, emphasizing the role of extracellular DNA (eDNA). Biofilms are a ubiquitous form of microbial life with significant implications in medicine, industry, and the environment. They are responsible for persistent infections, antibiotic resistance, and biofouling, leading to economic costs of billions of dollars annually and thousands of deaths. Biofilms consist of microbial communities encased in a polymeric matrix that provides mechanical stability and protection from mechanical stresses through its viscoelastic properties. While the linear viscoelastic response under small deformations is well characterized and recognized as a virulence factor, the response to large deformations remains poorly understood. Notably, there is a lack of systematic investigation concerning the nonlinear regime, where externally applied loads can induce stress-hardening and stiffening of the biofilm matrix.

Recent findings from our group suggest that eDNA may play a central role in the stress-hardening of biofilms. We hypothesize that this behavior arises from the entropic elasticity of the eDNA network—a mechanism well described in polymer physics but largely unexplored in living biofilms. This could enable both short- and long-term adaptation to flow fluctuations. While initial experiments are consistent with this hypothesis, further investigation is necessary to validate the underlying molecular mechanisms and determine whether stress-hardening is specific to streamers or constitutes a broader feature of biofilm mechanical adaptation across various morphologies. This project will test these hypotheses through a combination of structural, biochemical, and rheological analyses of the biofilms and mathematical modeling, potentially revealing fundamental principles of biofilm resilience.

Job Description

• Experimentally investigate nonlinear rheology and stress-hardening in bacterial biofilms of different morphologies using custom microfluidic and rheometry platforms.
• Quantify the role of eDNA and its interactions with biofilm matrix components using mutant libraries, enzymatic/antibody assays, and controlled physicochemical conditions; assess incorporation of exogenous DNA into biofilms and its impact on morphology and mechanics.
• Develop and apply advanced fluorescence/confocal imaging approaches to resolve biofilm network structure and eDNA conformation in situ.
• Contribute to the development of a numerical predictive model of biofilm mechanics.
• Collaborate within an interdisciplinary team and with external partners; communicate results through publications and presentations.

The tasks will include wet-lab experimentation, project management, numerical modeling, and teaching duties.

Position Details

Start date: February 1st, 2026, or by agreement.

This is a fully funded PhD position (approximately 4 years). Final admission to the doctoral program follows a successful Aptitude Colloquium at the end of year 1; contracts are extended annually.

Profile

The ideal candidate holds a Master’s degree in:

• Physics, biophysics, materials science, microbiology, or a related field with a strong interest in interdisciplinary research at the interface between soft-matter physics and microbiology.
• Experience in experimental work such as microfluidics, rheology, microscopy, or culturing microbes, alongside familiarity with data analysis and quantitative modeling is highly valued.
• The candidate should be motivated to work both independently and collaboratively within an international research environment and contribute actively to teaching activities.

Workplace

Our lab is located at ETH Zurich, a global leader in science and technology education and research.

We Offer

• Training opportunities
• Prospects for career development
• Support programs (e.g., mentoring) and networks
• A positive team culture and collaborative environment
• Attractive working conditions and employment environment
• Commitment to diversity, including flexible working hours, part-time opportunities, and options for remote work

We Value Diversity and Sustainability

In alignment with our values, ETH Zurich fosters an inclusive culture. We promote equal opportunities, value diversity, and cultivate a working environment that respects the rights and dignity of all staff and students. Sustainability is a core principle for us; we are consistently working towards a climate-neutral future.

Curious? So Are We.

We look forward to receiving your online application, which should include the following documents:

• Curriculum vitae
• Cover letter (including motivation, research interests, and possible start date)
• Full transcript from undergraduate studies (both Bachelor and Master's)
• Copy of the Master’s or Bachelor’s thesis (PDF)
• At least two reference letters

Only applications matching the job profile will be considered. Please apply online using the form below.

For inquiries regarding the position (but not for submitting applications), please contact Dr. Eleonora Secchi at esecchi@ethz.ch.

About ETH Zurich

ETH Zurich is one of the world’s leading universities specializing in science and technology. We are renowned for our outstanding education, cutting-edge fundamental research, and direct transfer of new knowledge into society. Over 30,000 individuals from more than 120 countries find our university to be a place that promotes independent thinking and inspires excellence. Situated in the heart of Europe while forging connections around the globe, we work collaboratively to develop solutions for the global challenges of today and tomorrow.