One of the coolest bits of manufacturing tech I've seen is laser-printed circuit traces on plastic. There are a couple different ways to do it, but in any case you can print gold traces onto 3D objects, even concave ones. It gets used to print antennas onto plastic for phones and whatnot. The tech is a little bit exotic but it's purchasable by even a small R&D group, don't have to be Apple to get it.