Electrophoretic core-shell particles having an organic pigment core and a shell with a thin metal oxide layer and a silane layer

An electrophoretic medium comprising a plurality of a first type of core-shell particles and a non-polar fluid, wherein each of the plurality of the first type of the core-shell particles comprises:

• a core comprising an organic pigment;
• a shell comprising a metal oxide layer and a silane layer;
• wherein the metal oxide layer is formed on the surface of the organic pigment using a fluidized bed reactor by inserting the organic pigment into the reactor as a powder bed, contacting the powder bed with a gaseous stream comprising an inert gas and a metal oxide precursor, and contacting the powder bed with a gaseous stream of an inert gas and a reagent that reacts with the metal oxide precursor to form a metal oxide;
• and
• wherein the silane layer is formed from a silane compound comprising a first functional group and a second functional group, wherein the first functional group reacts with the metal oxide, and the second functional group is selected from the group consisting of a carboxy group, a sulfate group, a sulfonate group, a phosphate group, and a phosphonic group.