Researchers convert chemical energy into rotational energy at the supramolecular level

Researchers at the Technical University of Munich (TUM) have developed an artificial motor at the supramolecular level that can develop impressive power. This wind-up motor is a tiny ribbon made of special molecules. When energy is applied, this ribbon aligns itself, moves like a small fin and can thus push objects. For the first time, the energy for this comes from a chemical fuel.

Until now, the conversion of chemical energy into rotational energy on a supramolecular level, i.e., for small objects consisting of more than one molecule, was only known from biology. Primitive bacteria, known as archaea, use the chemical fuel ATP to rotate their tiny fin-like locomotion organs, the flagella, and thus move around.

Synthetic replicas of this process have not existed until now. In the future, the new development could be used in nanorobots that swim through blood vessels to detect tumor cells, for example.

Chemical fuel drives the rotation

The peptide ribbons developed by a team led by Brigitte and Christine Kriebisch and Job Boekhoven, Professor of Supramolecular Chemistry, are a few micrometers long and just a few nanometers wide. When chemical fuel is added, they gain structure and the ribbons curl up into small tubes, causing them to begin to rotate. This process can even be observed live under the microscope.

The researchers discovered that they can control the rotation speed of the ribbons by the amount of fuel added. In addition, the direction of rotation—clockwise or anti-clockwise—can be influenced by the structure of the molecular building blocks of the ribbons. The research results were published in Chem.

Crawling on surfaces

Together with Prof. Matthias Rief, TUM Professor of Molecular Biophysics, who works on state-of-the-art optical measurement methods, the researchers found that the ribbons exert enough force on their surroundings to move micrometer-sized objects. Determining the force is one of the most important results for practical use.

If several rotating ribbons are brought together at a central point, for example, small “micro-walkers” are created that can crawl along surfaces. In the future, after further improvements, these micro-walkers could possibly be used for medical applications such as transporting drugs in the body. The fuel used is not yet suitable for this, as it would be harmful to the organism.