Michael Schlüter

Could you start by telling us a bit about your background? How did you begin your career, what did you study, and what have you done up until today?

Sure. I studied mechanical engineering and process engineering at the University of Bremen. After that, I worked at the Institute of Environmental Process Engineering, where I first came into contact with multiphase flows. By multiphase flows, I mean systems where we have a liquid phase as the continuous phase, and within this liquid phase, there are bubbles, droplets, and solids. My research focused on these types of flows, which are crucial in areas like wastewater treatment, biotechnology, chemical, and pharmaceutical industries.

Initially, in Bremen, I focused on wastewater treatment. However, I found the idea of transitioning into pharmaceutical and chemical production more intriguing. This led me to take up a professorship in fluid mechanics of multiphase flows at the Hamburg University of Technology in 2019. Now, I lead the Institute of Multiphase Flows, where I work on projects related to pharmaceutical and chemical engineering, alongside fundamental research funded by the German Research Foundation.

One interesting project related to SOPAT was conducted in the deep sea of the Gulf of Mexico, where we measured droplet size distributions under deep-sea conditions.

Could you explain more about the project in the Gulf of Mexico?

Certainly. The core issue in these projects, whether in the Gulf of Mexico or in a pharmaceutical fermenter, is understanding how much mass transfers from a droplet or bubble to the liquid phase. For example, during the Deepwater Horizon catastrophe, it was crucial to determine how much oil was entering the Gulf. Similarly, in pharmaceutical engineering, we need to know how much oxygen is transferred from gas bubbles to cells in drug production. The same principle applies in chemical engineering.

SOPAT technology helps us measure particle size distributions—be it bubbles or droplets— which is essential for understanding mass transfer. In the Gulf of Mexico project, we collaborated with Professor Claire Paris from the University of Miami, who used our data to simulate ocean currents and predict where the oil would end up. Our experiments provided her with the necessary particle size distributions to make these predictions accurate.

You’re the head of the Institute of Multiphase Flows. Are you currently involved in any other research projects?

Yes, I’m involved in both fundamental and industrial research. For fundamental research, we’re working on a project funded by the German Research Foundation that focuses on fine bubbles. These microbubbles are particularly interesting because of their small size, which allows them to follow flow patterns very closely, even in complex environments. They have a low pressure drop and provide a high mass transfer performance due to their large interfacial area. However, there’s still much to learn about how to produce and utilize these bubbles effectively, which is where SOPAT plays a role.

On the industrial side, we’re working with companies on scaling up processes from laboratory to industrial scale. For example, we use SOPAT to measure bubble or droplet size distributions in lab experiments and then apply that knowledge to predict behavior in large-scale industrial reactors. This is crucial for ensuring that industrial systems behave as expected. We also use this data to validate numerical simulations, a process that’s becoming increasingly important in industrial research.

When did you first start using the SOPAT system, and how did you learn about it?

We’ve been using SOPAT for a very long time—probably since around 2015, shortly after the company was founded in 2012. I first encountered SOPAT at the ACHEMA fair, a major international trade show. I was immediately impressed by the possibilities of the technology. We discussed internally and decided to acquire our first SOPAT system that same year. I’ve known Sebastian for a long time, even before he founded SOPAT, so I’ve been following the company’s growth closely.

How do you use SOPAT systems at your institute, and what sets them apart from other technologies?

We have several SOPAT systems, each tailored to specific needs. For instance, for our deep-sea research, SOPAT provided us with a probe that could withstand pressures up to 150 bars, which was essential for our work. SOPAT’s ability to customize systems based on our requirements, such as chemical resistance, has been incredibly valuable.

Compared to other technologies, SOPAT’s major advantage is that it allows us to take measurements directly within the flow, even in high gas hold-ups where traditional methods struggle. Another significant benefit is the visual aspect—the ability to see actual images of the particles. This visual data allows us to validate results and investigate any anomalies, something other systems can’t offer. For spherical particles, the SOPAT software works very well, although we’re still working on improving results for more complex, three-dimensional shapes.

It seems like you’ve had a lot of success with SOPAT. How do you see the future of this technology?

I believe more companies are recognizing the importance of understanding particle size distributions. In the past, processes were often a ‘black box,’ but now there’s a growing focus on process improvement, which is directly linked to particle and bubble size. As this understanding deepens, I’m confident that SOPAT technology will become increasingly vital, not just in research but also as part of quality control in production lines. SOPAT is on the right track, and I foresee it playing a crucial role in inline process analytics in the future.