Microswimmers from Toposelective Nanoparticle Attachment

Microswimmers hold promise for applications ranging from targeted delivery to enhanced mixing at the microscale. However, current fabrication techniques suffer from limited throughput and material selection. Here, a versatile route enabling the synthesis of microswimmers from off-the-shelf micro- and nano-particles is demonstrated. The protocol hinges on the toposelective attachment of photocatalytic nanoparticles onto microparticles, exploiting a multi-functional polymer and a Pickering-wax emulsification step, to yield large quantities of photo-responsive active Janus particles. The polymer presents both silane and nitrocatechol groups, binding silica microspheres to a range of metal oxide nanoparticles. The Pickering-wax emulsions protect part of the microspheres' surface, enabling asymmetric functionalization, as required for self-propulsion. The resulting photocatalytic microswimmers display a characteristic orientation-dependent 3D active motion upon ultra-violet illumination, different from that conventionally described in the literature. By connecting the extensive library of heterogeneous nanoparticle photocatalysts with the nascent field of active matter, this versatile material platform lays the groundwork toward designer microswimmers, which can swim by catalyzing a broad range of chemical reactions with potential for future applications.

Automated summary

A new method for fabricating microswimmers using photocatalytic nanoparticles and microparticles was demonstrated, allowing for the production of large quantities of photo-responsive active Janus particles. The resulting microswimmers exhibit unique 3D active motion under UV illumination, laying the groundwork for designer microswimmers that can catalyze a broad range of chemical reactions for potential future applications.