The first one is a perlin vector field plus a deformation. I haven't heard of those artists but I will look them up.

On the brush: That's a chinese calligraphy brush. I spent a bunch of time making a bearing holder to let the brush swivel freely. It didn't work. The brush is very, very hard to get to behave. A human will tilt it slightly in order to get the bristles to go in the right direction, but the CNC machine keeps everything completely orthogonal. Works for pens but not brushes.

Edit: Keith Peters' algorithmic stuff ( http://www.artfromcode.com/ ) does seem to share a lot of the same underlying techniques. Perlin flow fields and hex truchet tiles especially.