Characterization of the swelling behaviour of model (bio)films

Field: applied chemistry / biochemistry / physics / material science
Duration: min. 3 months (start: winter 2017/2018)
Allowance: 350 € / month

Suitable as a BSc or MSc thesis project, or internship. The research activities take place at both Wetsus (Leeuwarden) and Wageningen University.


Biofilms grow when microorganisms start accumulating and growing on surfaces. For protection and fixation reasons they surround themselves with a slimy layer of extracellular polymeric substances (EPS), containing all kinds of polysaccharides, proteins, cell fragments, inorganic particles, etc. This is especially unwanted on membranes as they are commonly used e.g. in (drinking) water treatment, because the flux through these membranes is hindered. In this case the layer is referred to as biofouling.

In the biofouling theme of Wetsus we are investigating the growth and strength of biofilms in order to find smart solutions to prevent or remove them. One step on the way there is to understand the interactions between the different components of biofilms. For this artificial model (bio)films as well as lab-grown films are investigated.

Project description

One not yet well investigated phenomenon is the swelling behaviour of biofilms. Since water is usually abundantly available in the observed systems, the swelling is dependent on the interactions between the films’ components and those in solution, as well as on other environmental influences such as pressure, temperature, etc. Naturally, the water content has a high impact on the mechanical behaviour of the films.

The starting point for this project is that for films consisting of one model compound “growth” through swelling has been observed for at least 10 days. For the reference component alginate, on the other hand, it has been described that a swelling balance is reached within 24h1. For biofilms this phenomenon has, to my knowledge, not been investigated in this form yet.

Your task will therefore be the characterization of the model films concerning their swelling behaviour depending on their composition and the environmental surroundings. For this you will prepare the films in dead-end filtration systems and then follow their swelling using optical coherence tomography (OCT, see Figure 1). Depending on time and results we can later expand the project to comparison with lab-grown biofilms and/or the measurement of mechanical behaviour dependent on swelling state.


We are looking for a highly motivated, enthusiastic and independent student ideally with a background in material science, chemistry, physics or other related fields. We prefer candidates with a good team spirit, who appreciates the international research environment in Wetsus. Fluency in English is a requirement.


You feel excited about this project or still have questions? Just contact me! Interested students are invited to hand in a motivation letter (max. 1 page) and a CV (max. 1 page) to Natascha Pfaff (

1. Davidovich-Pinhas, Maya, and Havazelet Bianco Peled. 2010. “A Quantitative Analysis of Alginate Swelling.” Carbohydrate Polymers 79(4): 1020–27.