this is a quick way to set up, a writing effect in blender, using particle system and metal balls
the first thing you need is a curve and a plane
add a curve and a plane, select the plane then the curve and use the shortcut ctrl+P and select follow path. now when you play the animation, you will see the plane following the curve
add a meta ball object, this is going to be the particle instance when we add a particle system.
select the plane and add a particle system with the settings below, make sure the meta ball is the render as object in the render settings.
Meta ball settings
for the particles to show as ink the meta ball has to have the right settings, for viewport rendering and render. make sure the is enough resolution. and add an ink like material, here i used a principled bsdf with a dark color add 0 roughness for a very reflective surface.
if your animation is too fast or slow, control it by selecting the curve and going to the curve settings, under path animation you can control the speed of the animation by changing the frame count.
Download the project files here