Laser-induced forward transfer: a method for printing functional inks

Laser-induced forward transfer (LIFT) is a direct-writing technique based in the action of a laser to print a small fraction of material from a thin donor layer onto a receiving substrate. Solid donor films have been used since its origins, but the same principle of operation works for ink liquid films, too. LIFT is a nozzle-free printing technique that has almost no restrictions in the particle size and the viscosity of the ink to be printed. Thus, LIFT is a versatile technique capable for printing any functional material with which an ink can be formulated. Although its principle of operation is valid for solid and liquid layers, in this review we put the focus in the LIFT works performed with inks or liquid suspensions. The main elements of a LIFT experimental setup are described before explaining the mechanisms of ink ejection. Then, the printing outcomes are related with the ejection mechanisms and the parameters that control their characteristics. Finally, the main achievements of the technique for printing biomolecules, cells, and materials for printed electronic applications are presented.