Inkjet printing, digital inkjet printing, direct inkjet printing, polymer jetting, photopolymer jetting, rapid freeze prototyping, etc., are liquid deposition processes. If the material is not liquid, it is melted in order to be deposited. If it has a high melting point, e.g., ceramic, it is mixed in a carrier liquid. If it is a high molecular weight polymer, it is dispersed in a carrier liquid to make it low-viscous so that it can be ejected through a nozzle. The liquid should not be solidified either in the nozzle or after leaving it and should reach a substrate in the state of liquid. Besides, the liquid composition should not change due to chemical reaction, physical segregation, or evaporation. It can reach in the form of either a continuous stream or drops. But the continuous stream has a propensity to break before it reaches; therefore, the liquid deposition is a dropwise deposition. The process can thus be controlled by controlling the ejection of drops.