Abstract: The invention provides methods and apparatus for encapsulating particles. An inverted selective withdrawal technique is employed. Two immiscible fluids are added to a container, a first fluid is an aqueous pre-polymer solution with a crosslinking reagent and a second fluid is denser highly viscous fluid. A selective withdrawal tube pulls particles suspended in the first fluid through the second fluid. The particles retain a thin coating of the first fluid. The coated particles are then subjected to a crosslinking process where the pre-polymer solution of the first fluid surrounding the particles is converted into a hydrogel capsule.