methods and apparatus are described for delivering index - matching immersion liquid in high numerical - aperture optical microscopy and lithography . an array of immersion liquid droplets is delivered to a specimen substrate or specimen substrate cover by an immersion liquid printing apparatus . an immersion liquid reservoir provides immersion liquid to the printer by a precision pump . the printer delivers immersion liquid to the substrate or substrate cover in arrays of immersion liquid droplets of defined volumes and array patterns . the volumes and patterns of array droplets delivered to the substrate or substrate cover are optimized to maintain adequate immersion liquid between the substrate or substrate cover and an immersion objective while avoiding the formation of air bubbles in the immersion liquid and the accumulation of excess volumes of immersion liquid .