the average fiber diameter as a function of relative humidity the charged jet solidified at the largest diameter when electrospun at low humidity since water in the jet evaporated rapidly when the charged jet becomes very thin the charges carried by the jet move further apart the surface area increases and the charge per unit area on the surface of the jet decreases the development of the capillary instability creates thin fiber segments between beads with diameter larger than the fiber beaded fibers appeared at 51 relative humidity and higher the capillary instability of a fluid jet which causes a cylindrical jet to break up into droplets is a well known phenomenon the surface energy of fluid in the form of a jet is higher than that of same volume of liquid in the form of drops several factors are known to affect the formation of beaded fibers the volume of the beads relative to the volume of the fibers increased when electrospun under higher relative humidity when the fibers were thinner the bead diameter increased the length of the beads decreased and the spacing between beads becomes smaller as shown in fig3 and fig4 which shows the average bead diameter bead length and distance between beads at different relative humidity the solid line in fig3 shows the average fiber diameters at different relative humidity and it the linear fit of the average fiber diameter ignoring the beads the average fiber diameter decreased sharply when beads started to occur at 52 6 relative humidity the total volume of polymer per unit length of.