Endre Joachim Mossige

Visiting Postdoctoral Researcher

Oslo, Norway

Education

PhD Microfluidic particle and cell separation, University of Oslo (UiO), Norway, 2017
MSc Mechanical Engineering, Norwegian University of Science and Technology (NTNU), Norway, 2011
Exchange Year, University of California, Santa Barbara (UCSB), USA, 2009

Research Focus

Rayleigh-Taylor instabilities in aqueous polymer solutions

The Rayleigh-Taylor (RT) instability can occur when a heavy fluid rests on top of lighter fluid and is often observed as spikes of the heavier fluid descending through the lighter fluid. This instability has been well described for immiscible and miscible systems, however few studies have focused on aqueous polymer solutions. Our resent measurements show that polymer solutions can spontaneously exhibit the RT instability in these systems, which are present in many technical situations. We use both fluorescent and brightfield imaging to characterize the onset and evolution of this spontaneous RT instability.

Diffusion in drops: Effects of ultra-low interfacial tension

Flows characterized by high interfacial tension such as bursting bubbles and splashing drops are relatively well understood, while flows involving liquids of ultra-low interfacial tension have received less attention. One famous example of such a flow is the mixing of milk and coffee, which is a process that is controlled by diffusion. In this project, we will expand previous studies of miscible liquids, by introducing aqueous polymer solutions. These solutions occur frequently in drug delivery systems and in food production processes, but the role of diffusion on the dynamics and stability is not fully understood. To gain understanding of these fascinating systems, we study sessile drops as well as coalescing drops by means of optical methods. Figure 1 shows how fluorescence enhances the contrast between the liquid phases in a coalescing drop experiment. Fluorescence imaging can also be used to measure the diffusion of polymer.

Previous research experience

During my PhD, I demonstrated how tunable flow fields can be used to sort particles and complex algal cells at high throughput in a microfluidic filter. By utilizing hydrodynamic interactions between particles, filter structures and the tunable flow fields, I showed how separation can be performed without clogging. I employed fluorescence imaging to characterize these hydrodynamic interactions and velocimetry techniques (Particle Image Velocimetry (┬ÁPIV) and Particle Tracking Velocimetry (PTV)) to quantify the flow and particle velocities. Figure 2 is a streakline visualization which shows trajectories of separation particles (thick streaks) near the filter structures. The thin streaks represent the fluid flow.

Figure 1
Figure 1. A droplet of light polymer material rising in a heavier polymer material due to buoyancy. Fluorescent dye is used to increase the optical contrast.

Figure 2
Figure 2. Streakline visualization that shows clog-free, hydrodynamic separation of particles in a microfluidic filter. The thick streaks represent the particles and the thin streaks represent the fluid flow.