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 seeking two PhD candidates. Our research aims to uncover the physicochemical mechanisms that control microbial surface colonization, biofilm assembly, structure, and rheology. We employ a diverse array of technologies from materials science, microbiology, and microfluidics, in addition to advanced imaging techniques, to tackle our research questions. Our team comprises approximately 10 members and thrives in an interdisciplinary, international, and collaborative environment, hosted within the chair of Prof. Roman Stocker in the Institute of Environmental Engineering.

Project Background

The two PhD positions are integral to a recently funded SNSF project that seeks to systematically investigate nonlinear biofilm rheology, with a specific focus on the role of extracellular DNA (eDNA). Biofilms represent a ubiquitous form of microbial life with significant implications for medicine, industry, and the environment. They contribute to persistent infections, antibiotic resistance, and biofouling, leading to economic consequences amounting to billions of dollars annually and countless health risks. Biofilms are microbial communities encased in a polymeric matrix that provides mechanical stability and protection against stresses due to their 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. There exists a critical gap in systematically investigating the nonlinear regime, where externally applied loads can induce stress-hardening and stiffening of the biofilm matrix.

Recent insights from our group indicate that eDNA might play a pivotal role in the stress-hardening of biofilms. We hypothesize that this behavior is linked to the entropic elasticity of the eDNA network, a mechanism extensively described in polymer physics yet largely unexplored in living biofilms. This understanding could enable both short- and long-term adaptation to flow fluctuations. Initial experiments support this hypothesis, but further investigation is essential to validate the underlying molecular mechanisms and to ascertain whether stress-hardening is unique to specific morphologies or represents a broader characteristic of biofilm mechanical adaptation. This project will rigorously test these ideas through a combination of structural, biochemical, and rheological analyses of biofilms, alongside mathematical modeling, with the potential to unveil fundamental principles of biofilm resilience.

Job Description

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

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

Position Details

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

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 of soft-matter physics and microbiology.
• Experience in experimental work such as microfluidics, rheology, microscopy, or culturing microbes is highly valued, alongside familiarity with data analysis and quantitative modeling.
• The candidate should be motivated to work both independently and collaboratively within an international research environment and contribute actively to teaching activities.

Workplace

Your workplace will be in the vibrant research environment of ETH Zurich, renowned for its commitment to excellence and innovation.

We Offer

• Training opportunities
• Career development perspectives
• Support programs (e.g., mentoring) and networks
• A collaborative and inclusive team culture
• A conducive working environment with favorable employment conditions
• Commitment to diversity, including flexible working hours and options for part-time work or home office arrangements

Our Commitment to Diversity and Sustainability

ETH Zurich promotes an inclusive culture, prioritizing equality of opportunity and valuing diversity. We nurture a working and learning environment that respects the rights and dignity of all staff and students. Sustainability is a core value—our efforts continuously aim for a climate-neutral future.

Curious? So Are We.

Apply online using the form below. We look forward to receiving your application by November 30th, 2025, 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 Master’s or Bachelor’s thesis (PDF)
• At least two reference letters

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 is one of the world’s leading universities specializing in science and technology. Renowned for our excellent education, pioneering research, and seamless transfer of knowledge into society, we attract over 30,000 individuals from more than 120 countries, fostering an environment that inspires independent thinking and excellence. Situated in the heart of Europe while maintaining global connections, we work together to develop solutions for today’s and tomorrow’s global challenges.