Artificial cilia and 2 Photon Crosslinking

Hairy surfaces (AKA cilia) are commonly found in nature for a wide variety of purposes. For example, Paramecium, a tiny organism, uses cilia as paddles for swimming around in water. In our lungs, cilia restlessly transport all the unwanted mucus out of our body. These two examples alone show the fascinating capabilities of cilia surfaces.

Paramecium bursaria. Image by Anatoly Mikhaltsov, CC BY-SA 4.0

Accordingly, due to their many capabilities, artificial cilia have become an exciting area of research in technology, particularly for developing micro-actuators. These tiny devices are inspired by the movement of cilia and could be utilized for pumping or mixing small volumes of liquids in a miniaturized lab on a chip device.

Nicolas Geid, a CPI researcher, has embarked exactly on this topic. Geid has combined chemistries that were developed within the CPI group with 2 Photon Lithography to generate microactuator fields that resemble, to a certain degree, their biological models.

In his system, he uses surface-bound 3D micro-magnets made from photoreactive copolymers filled with magnetic nanoparticles. These structures are generated by maskless 3D writing using a technique called 2-photon crosslinking (2PC). This method allows for direct writing into solid films of composites consisting of magnetic particles and a photoreactive elastomer precursor.

With this approach, it is possible to directly write complex, surface-bound magnetic actuator structures. This opens up new opportunities in the fields of microfluidics and bioanalytical systems. Compared to the common 2-photon polymerization, in which the writing process takes place in a liquid resin, the direct writing based on the 2PC method takes place in a solid polymer film (i.e., in the glassy state).

The article can be freely accessed on the journal's webpage.

Nicolas Geid, Jan Ulrich Leutner, Oswald Prucker and Jürgen Rühe
Maskless Writing of Surface-Attached Micro-Magnets by Two-Photon Crosslinking
Actuators 2023, 12, 124.
DOI: 10.3390/act12030124