Science Buddies: "Ask an Expert"

what is the principle of a gel pen? what function do the 'gel' do

here you go:

"What distinguishes a gel pen from a ballpoint pen is the gel ink. It consists of pigment suspended in a water-based gel. The pigments are typically copper phthalocyanine and iron oxides, and the gel is made up of water and biopolymers, such as Xanthan gum and tragacanth gum, as well as some types of polyacrylate thickeners. Since pigments are opaque, gel pens are available in bright colours that stand out on dark paper."

http://en.wikipedia.org/wiki/Gel_pen