Job University of Twente - PhD Position Influence of wall roughness and particle adhesion on confined flows

Confined flows of colloidal suspensions are increasingly found in Lab-on-a-Chip applications. However many fundamental insights are still missing.This applies especially to the aspect of roughness of the confining walls, which can present itself as corrugations in the native wall material, or as particles that get adsorbed from the fluid. The local structure and dynamics of the fluid and consequently also its flow behavior, can be changed profoundly by the roughness. In particular a strong coupling between wall roughness and wall slip is expected. However, experimental studies on colloidal lengthscales have been scarce, and mechanistic insights are largely missing.

The project will focus on the dynamics of particles near walls with various types of roughnesses, with and without adhesiveness. Whether or not slip will occur, depends on a competition between geometric and thermodynamic ‘holding’ forces, and ‘disruptive’ forces related to the suspension rheology. Each of these aspects will be taken into account. Concentrated suspensions will be studied inside micro channels under the application of different flow strengths. Real-time CSLM will be used to visualize the particles’ structure and dynamics at the wall and in 3D across the channel. Cleanroom technology and silane chemistry will be used to obtain an independent control over wall roughness and stickiness, respectively.

One particular kind of roughness is obtained by fouling, which generally involves a progressive attachment of particles from the suspension to the wall. To understand the relation between fouling and wall slip, we will also do experiments in which the degree of surface coverage is actively controlled. For this we shall develop walls with embedded micro-electrodes, that can be switched on/off individually in order to let particles stick/unstick.

For this challenging project we are looking for enthusiastic candidates with a background in experimental physics, physical chemistry or chemical engineering. He or she should have relevant experience in at least one of the fields of rheology, colloids and microfluidics.

The assignment is for 4 years, with a go/no-go assessment at the end of the first year. The candidates are expected to finish the project with a PhD thesis and disseminate the results through patents (if applicable), publications in peer-reviewed journals and presentations at international conferences.

Your starting salary will be € 2042, - in the first year and up to € 2612, - gross per month in the last year.

University of Twente. A place where talent emerges and develops. Students and staff are our valued core. Approximately 3,300 scientists and professionals work together on groundbreaking research, relevant innovation and inspiring education for more than 9,000 students.

The Faculty of Science and Technology (700 faculty members, 1100 students) offers a range of bachelor and master courses (NanoTechnology, Applied Physics, Chemical Engineering and Technical Medicine). The faculty’s research is organized in three of the university’s interdisciplinary research institutes: MESA⁺, MIRA, and IMPACT. These institutes increase the vitality of research by enabling collaboration between programs and disciplines, by providing shared facilities, and by attracting funding for joint projects. They also provide a conduit to industrial and other external partners.

For more information please contact Dr. Michel H.G. Duits (+31-53-489-3097; M.H.G.Duits@utwente.nl)