Automated defenses were no match for the Furling. They breached the iris without mercy.
Chickens
I suggest a shape such as below, pointing down, with a hole too small to admit the mice, and too smooth to get a grip on. Also, mice can only jump so high, so mounting it as high as possible with no route up would help, too (or maybe even be the entire solution.) Of course, it needs a hatch and might need a shaking device to keep the food moving. Pellet food with a consistent size would work better.
3D prints can be sanded and painted to create a glossy smooth surface: https://youtu.be/P5-jtvYlA1c
To avoid reinventing the wheel, I'd buy a dry food dispenser with a spinny handle and attach a servo.
