Until now, it has been technically almost impossible to rotate highly sensitive samples in all directions under a microscope without contact. Researchers at Karlsruhe Institute of Technology (KIT) have developed a new laser-based technique that allows microscopic samples, such as cells, to be rotated in all three spatial directions without contact. The laser creates a small temperature difference within the liquid, which causes a gentle liquid flow that moves the sample. This protects delicate samples and allows for more accurate three-dimensional images. This is an important step for basic medical research.
Although modern optical microscopes can produce extremely sharp images comparable to photographs within a single plane, depth information is often inaccurate. To overcome this limitation, it is necessary to image the sample from multiple viewing angles and combine the images into a three-dimensional model. This requires rotating the object being investigated. A new method makes it possible to do this in a very gentle way.
Rotation without physical contact
The research team, led by Professor Moritz Kreising and Dr. Van Nan from the KIT Institute for Biochemical Systems, uses a laser to locally heat the liquid in which the sample is suspended. This generates subtle fluid flows that can be used to precisely move freely floating microscopic objects without the use of any mechanical microtools such as small pipettes, needles, or grippers.
“We don’t manipulate the samples directly,” Nunn says. “Instead, it controls the movement of the surrounding fluid so that the object aligns itself.”
Laser-driven flow has been known for some time, but until now it was only possible to operate in a single plane. Controlled rotation in three-dimensional space is now also possible. By scanning a laser at high speeds, the researchers create a spiral flow that gently rotates the object. This is similar to a small paper boat spinning on its own in a small whirlpool.
Benefits for healthcare and technology
Three-dimensional control allows you to more effectively capture cell structures from various perspectives.
The more accurately the sample can be aligned, the more detailed information will be displayed. This is an important prerequisite for a deeper understanding of biological structures and processes. ”
Professor Moritz Kreising, KIT Institute for Biochemical Systems
In the long term, Kreysing says, the method could also be relevant for non-contact micromanipulation, microscopic robotics or high-precision manufacturing at the smallest scales.
sauce:
Karlsruhe Institute of Technology
Reference magazines:
So, F. others. (2026) Spiral photothermal viscous flow drives out-of-plane rotation and particle rotation within a highly viscous microenvironment. Light: Science and Applications. DOI: 10.1038/s41377-026-02303-8. https://www.nature.com/articles/s41377-026-02303-8
