Experimenting with a 3d printed air filter. To print this out use 0.35 extrusion width and 0.300 layer height. Have a nice and level bed. Wax free dental floss to make it easier to remove from print bed. Sliced with the Slic3r slicer. Make sure your slicer is not removing thin walls. ("detect thin walls" in Slic3r) 9-1-15: more experimenting, created a version to mount directly to a 120mm fan. Seems to work but still room for improvements.