Hollowpixel shows how to create a blink using non-linear shape keys in Blender.

It’s likely that all DCCs that allow you to create blend shape, or as in Blender’s case, shape keys, also work linearly. That is to say that if you are trying to blend an eyelid shape around an eye, the lid will move in a line rather than how you’d like.

This tutorial from Chris McFall (Hollowpixel Studios) shows using a non-linear shape key technique to set up a blink with vastly improved animation. McFall uses the XYZ shape key script, which you can get here.