I believe the Poofs and AM (
they sell 1 al gear) had their gears anodized and teflon-impregnated. I don't claim to know much about Materials Science, but I'd be wary of using aluminum gears. In my experience, rubbing aluminum on aluminum doesn't work too good.
Would I use al gears in a manipulator? Absolutely.
Wouldn't bother with sprockets. You can just attach an AM sprocket to a hub and make a good al sprocket, which requires no broaching.