1 October 2026
How do liquids flow when gravity hardly plays a role? The Jülich Mini Rheometer (MiR) is set to embark on a journey from Kiruna aboard the MAPHEUS research rocket of the German Aerospace Center (DLR).
The device, which is about five centimeters in size, measures flow behavior and requires only a single drop of sample. During about six minutes of microgravity, it is set to demonstrate its functionality in space for the first time. MiR was developed jointly by several Jülich institutes. Pavlik Lettinga from the Institute of Biological Information Processes, Knut Dahlhoff from the Peter Grünberg Institute, and Simon Gottschalk from RWTH Aachen University explain the scientific possibilities the device opens up and what it must accomplish during the rocket flight.
What does MiR measure?
Pavlik Lettinga: A rheometer measures the flow behavior of a liquid: How much does the sample resist rotational motion, and how does the motion alter it? Unlike conventional rheometers, MiR requires only a single drop. It can be operated on a microscope. This allows us to simultaneously observe tiny particles in the liquid that influence its flow behavior.
Why is microgravity scientifically interesting?
Pavlik Lettinga: In some liquids, such as blood, particles can settle to the bottom. This sedimentation makes it difficult to measure flow behavior. Under microgravity, we expect the particles to remain evenly distributed. Then we might measure behavior that is completely different from what we see on Earth.
What was the biggest challenge during construction?
Knut Dahlhoff: The smaller the device, the higher the demands on the precision of the components and the measurement system. To achieve this, we use SLE technology, known as selective laser-induced etching. A laser etches patterns into quartz glass with micrometer precision. This creates tiny, precise components.
How did the Jülich institutes collaborate?
Simon Gottschalk: It all started with a question from the Institute for Biological Information Processes (IBI-4) asking whether such a mini-rheometer was even possible. This was complemented by the engineering expertise of the Institute of Technology and Engineering (ITE). My doctoral thesis grew out of this development.
Knut Dahlhoff: MiR combines mechanics, electronics, and software. The ITE contributed space-qualified electronics, software, and electromechanical components. The IBI workshop quickly manufactured key mechanical components using a highly precise 3D printer.
How did the lab device become an experiment for the rocket?
Knut Dahlhoff: We have to secure sensitive parts for launch and landing. To do this, we use a servomotor from a model airplane. The electronics were also newly developed. The compressed-air supply for the low-friction air bearings of the measuring drive was particularly tricky. In space, a pump from a blood pressure monitor handles the supply.
Pavlik Lettinga: We implemented development steps on short notice, especially with 3-D-printed parts. We also integrated a camera as well as pressure and temperature sensors.
When will the first flight test be successful?
Pavlik Lettinga: First, we need to see if the rheometer rotates properly. There are still many challenges to overcome for accurate measurements.
Knut Dahlhoff: We want to measure a specific sample, likely glycerin. If the viscosity-that is, the thickness-increases as expected as the temperature drops, that would be an indication that rheology is possible in space. But first, the priority is to ensure that the components function properly and withstand the stresses of launch and landing.
What new possibilities does MiR open up?
Pavlik Lettinga: I'm particularly interested in how biological systems develop and solidify in the absence of gravity. The combination of rheology and microscopy is essential here. The scientific collaboration on-site shows that this combination is indeed possible in space.
Knut Dahlhoff: A single drop of sample opens up new possibilities for scientific measurements. For a potential satellite application, we would need to develop an automated sample exchange system. This could also be useful in factories down the line.
