Dynamic in-fiber particle production with precise dimensional control

A method for producing particles comprising:

• providing a fiber that has been thermally drawn from a fiber preform, the fiber having a longitudinal-axis fiber length and including at least one continuous, solid fiber core having a longitudinal core axis parallel to the longitudinal fiber axis and internally disposed to at least one outer fiber cladding layer of cladding material along the fiber length;
• feeding the fiber through a localized heating site having a heating site temperature, T, at which a local viscosity of the fiber cladding material is greater than a local viscosity of the fiber core and at which an interfacial tension exists between the fiber cladding material and the fiber core, and which is above a melting temperature of the fiber core, the fiber being fed through the heating site at a fiber feed speed, υf, that melts a tip portion of the fiber core upon arrival of the tip portion at the localized heating site, causing a molten droplet to pinch off of fiber core material from the fiber core tip portion, producing a longitudinal sequence of molten droplets one droplet at a time, as the fiber is fed through the heating site, with a time period of molten droplet formation set by the fiber feed speed, υf, wherein the fiber feed speed, υf, produces solid particles having a diameter, d, as a function of fiber core diameter, D, as:
• d
• ≈
• D
• ·
• 3
• 4
• ⁢
• v
• f
• ⁢
• μ
• p
• clad
• γ
• p
• 3
• ,
• where μpclad is local viscosity of the fiber cladding material at the heating site temperature, T, and γp is interfacial tension between the fiber core material and the cladding material at the heating site temperature, T;
• and
• continually feeding the fiber through the localized heating site to move each molten droplet out of the localized heating site as each molten droplet is formed, to solidify each molten droplet, producing a longitudinal sequence of solid particles in the fiber, parallel to the longitudinal fiber axis, each particle being separated from other particles in the sequence by the fiber cladding material.