Facile fabrication of microlenses with controlled geometrical characteristics by inkjet printing on nanostructured surfaces prepared by combustion chemical vapour deposition

Precise positioning of microlenses with well-defined optical characteristics is key in the further development of CCD cameras, biosensors or optical fiber interconnects. Inkjet printing enables accurate microfabrication of microlenses however inks generally employed for this purpose contain solvents that need to be evaporated before the lens solidification process. Besides, the receiving substrate needs to be conditioned, sometimes using complex photolithographic steps to lead to large contact angles of the deposited ink drop that are needed to attain large numerical aperture microlenses. This paper describes the fabrication of microlenses with controlled geometrical characteristics by inkjet printing a solvent-free photocurable formulation. The employed photoacid catalyzed organic-inorganic hybrid ink can be cured just after deposition, without any intermediate evaporation or annealing step, enormously simplifying microlens fabrication process. Besides, a simple combustion chemical vapour deposition process, leading to a porous layer with nano-roughness, followed by a silanization step using a fluorosilane enables the generation of a surface that provides access to a large range of contact angles for the ink drops that are printed on this surface. Single droplet microball lenses with contact angles up to 115 degrees, beyond the hemispherical microlenses, are demonstrated with this industrially viable, cost-effective and high-throughput method.