Maybe more helpful: https://arxiv.org/ftp/arxiv/papers/2212/2212.08139.pdf
"‘Fluidic Shaping’, uses surface tension under neutral (or near neutral) buoyancy conditions to shape a volume of liquid into useful optical components by contacting it with a rigid bounding frame that serves as a spatial constraint. Neutral buoyancy is achieved using an insoluble immersion liquid that has equal density to that of the optical liquid. Both spherical and aspherical lenses, as well as freeform components, can be produced, with the specific topography controlled by the shape of the bounding frame and th…