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, led by Dr. Eleonora Secchi at ETH Zurich, is on the lookout for two enthusiastic PhD candidates. Our research delves into the physicochemical mechanisms that govern microbial surface colonization and the assembly, structure, and rheology of biofilms. We employ a diverse array of technologies from materials science, microbiology, and microfluidics, complemented by advanced imaging techniques. Our team is a vibrant, interdisciplinary, and international group comprised of approximately 10 members, operating under the chair of Prof. Roman Stocker at the Institute of Environmental Engineering.

Project Background

The two PhD positions are part of a recently funded SNSF project focused on systematically investigating nonlinear biofilm rheology, with particular emphasis on the role of extracellular DNA (eDNA). Biofilms are a prevalent form of microbial life, significantly impacting the medical, industrial, and environmental sectors. They contribute to chronic infections, antibiotic resistance, and biofouling, culminating in economic costs amounting to billions of dollars annually, along with thousands of fatalities. Biofilms consist of microbial communities encased in a polymeric matrix that provides mechanical stability and protection from mechanical stresses due to its viscoelastic properties. While the linear viscoelastic response under small deformations is well characterized, the response to larger deformations is not well understood. There is a notable lack of systematic investigation into the nonlinear regime, wherein externally applied loads can induce stress-hardening and stiffening of the biofilm matrix.

Recent findings from our group indicate that eDNA may play a pivotal role in the stress-hardening of biofilms. We theorize that this behavior results from the entropic elasticity of the eDNA network—a concept well-explored in polymer physics but largely uncharted in living biofilms. This could facilitate both short- and long-term adaptation to variations in flow. Initial experiments support this hypothesis; however, further investigation is warranted to validate the underlying molecular mechanisms and to discern whether stress-hardening is specific to streamers or represents a broader characteristic of biofilm mechanical adaptation across varying morphologies. This project aims to test these hypotheses through a seamless integration of structural, biochemical, and rheological analyses of biofilms, coupled with mathematical modeling, potentially illuminating fundamental principles of biofilm resilience.

Job Description

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

The position encompasses various responsibilities, including wet-lab experimentation, project management, numerical modeling, and teaching duties.

Position Details

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

Fully funded PhD position (approximately 4 years). Final admission to the doctoral program will follow a successful Aptitude Colloquium at the end of year 1; contracts are renewed annually.

Profile

The ideal candidate possesses a Master's degree in:

• Physics, biophysics, materials science, microbiology, or a related field, with a strong interest in interdisciplinary research bridging soft-matter physics and microbiology.
• Experience in experimental work, such as microfluidics, rheology, microscopy, or culturing microbes, along with familiarity in data analysis and quantitative modeling.
• A motivation to work independently as well as collaboratively within an international research environment, coupled with an eagerness to contribute to teaching activities.

Workplace

Located at ETH Zurich, our workplace promotes a culture of innovation and collaboration.

We Offer

• Training opportunities
• Career development perspectives
• Support programs (e.g., mentoring) and networking
• A cohesive team culture
• An inspiring working environment with favorable employment conditions
• A commitment to diversity (including flexible working hours, part-time work options, and work-from-home opportunities)

We Value Diversity and Sustainability

ETH Zurich is dedicated to fostering an inclusive culture. We promote equality of opportunity, value diversity, and nurture an environment where the rights and dignity of all staff and students are respected. Visit our Equal Opportunities and Diversity website to learn how we ensure a fair and open environment that supports growth and development. Sustainability is a core value for us, and we are continuously working towards a climate-neutral future.

Curious? So Are We.

We invite you to apply online using the form below. Only applications matching the job profile will be considered.

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

About ETH Zurich

ETH Zurich stands as one of the world’s leading universities specializing in science and technology. Renowned for our outstanding education and groundbreaking fundamental research, we are committed to transferring new knowledge directly into society. With over 30,000 individuals from more than 120 countries, we are a place that fosters independent thinking and inspires excellence. Situated in the heart of Europe, yet connected globally, we collaborate to address the pressing challenges of today's world and beyond.