Job description
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.
Requirements
For this challenging project we are looking for enthusiastic candidates with a background in 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.
Conditions of employment
In accordance with the university regulations for academic personnel, the gross salary of a Ph.D. student is € 2,042 in the first year to € 2,612 in the last year.
Contract type
Temporary
4 years
Organisation
University of Twente
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.
Department
http://www.universiteittwente.nl/education/tnw
Additional information
More information can be found at http://pcf.tnw.utwente.nl.
Further questions about this position can be addressed to Dr. Michel Duits (M.H.G.Duits@utwente.nl).
19.02
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