Patent ID: 7553542

Claim:
A functionalized magnetizable composite microsphere, comprising a core of magnetizable nano particles of a particle size ranging between 1-30 nm, the magnetizable nano particle having a monolayer of a non-water-soluble dispersing agent coated thereon; an inner shell of styrene polymer or styrene copolymer enclosing around the core magnetizable nano particle, and an outer shell of styrene polymer with sulfate (SO 4 ) bounded thereto, styrene copolymer with sulfate (SO 4 ) bounded thereto or ply(methacrylic acid) with sulfate (SO 4 ) bounded thereto enclosing around the inner shell, wherein the magnetizable microsphere have a size of 100-1000 nm and a thickness ratio of the inner shell to the outer shell ranging from 10:1 to 1:10.