Abstract: A method of preparing core-shell submicron spheres is disclosed. The method comprises steps hereafter. An emulsion containing a core monomer is heated to a temperature of 10° C. below its boiling point to the boiling point. A core forming step is performed by adding an initiator solution to the heated emulsion to form cores by polymerizing the core monomer. When the conversion of the above polymerization is 10% to 95%, a shell forming step is performed by adding a shell monomer into the emulsion, at a temperature of 50° C. below the emulsion's boiling point to the boiling point thereof, to form shells, respectively surrounding the cores, by polymerizing the shell monomer.

Abstract: A toothbrush with a safety device includes a brush body and an annular spacer. The brush body includes a bristle portion with a plurality of bristles and a handle portion contiguous to the bristle portion. The annular spacer is flared and includes a smaller end and larger end having a diameter greater than that of the smaller end. The smaller end of the spacer is tightly mounted around the handle portion below the bristle portion. The annular spacer avoids the toothbrush from being swallowed and prevents spit and bubbles generated during brushing from coming into contact with a user's hand.