I&J FISNAR INC.: Tapered Tip Needle
March 13, 2008
When dispensing high-viscosity fluids with standard blunt-end tips, extra pressure is required to overcome resistance when entering the straight needle tube. The effect of this extra pressure to overcome the resistance is the introduction of a tertiary element in the control of the dispensing process, making an accurate deposit difficult or even impossible to achieve. The tertiary element is the excess pressure, which pushes the fluid forward after air pressure is released either from a syringe or valve. A few high-pressure valves have a snuff-back feature, but it is impossible to successfully apply snuff-back when using a syringe for high-viscosity fluids. The solution is to use a tapered dispensing needle, which is a molded-plastic tapered design that prevents, or at least effectively reduces, the tertiary pressure phenomenon. These needles reduce the post-dispensing ooze that can be found with blunt-end tips, particularly when using high-viscosity fluid requiring higher pressure to dispense.