Active photo-responsive microgel-structured surfaces for triggered particle movement

• Applicants: Professor Dr. Andrij Pich; Professorin Dr. Svetlana Santer
• Subject Area: Polymer Materials ; Experimental Condensed Matter Physics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 544907265

Manipulation of colloids, particles or cells in microfluidic systems mostly proceeds by designing flow patterns globally via a suitable microchannel network and applying external pressure as well as electro-kinetic driving, or addressing one particle at a time with optical or magnetic tweezers. Exploiting combinations of local and global action as conveyed by, for instance, the beating of artificial magnetic cilia is still in its infancy though potentially offering great flexibility as in their biological role models. In this project, we essentially suggest a non-contact way of generating local-global, spatio-temporally varying hydrodynamic forces at a solid-liquid interface. Corresponding flow fields are generated by superimposing optical illumination patterns onto a pre-structured microgel film in the presence of a suitable ionic photo-responsive, azobenzene containing surfactant that can be switched between a hydrophilic cis- and rather hydrophobic trans- conformational state. The wavelength sets the ratio of cis-/trans concentration in the vicinity of the microgel, which in turn acts as an effective source/sink governing the spatial composition distribution, ultimately effecting a corresponding light-driven diffusio-osmotic flow. In this way, the lateral microgel pre-structuring sets the stage for generating a broad range of microfluidic flow patterns. Our approach can be of particular use for flat channel- or assay-like chambers to be used for controlled manipulation of single particles, filtration purposes or organization of particle- or cell ensembles for optical readout, thus implementing a laboratory-in-a-chamber.

• DFG Programme: Research Grants