Making solar cells like this is a nice first step to making self replicating machines. Being able to make solar cells is especially interesting because these ar

Making solar cells like this is a nice first step to making self replicating machines. Being able to make solar cells is especially interesting because these are semiconductor devices, so producing control electronics may be possible too. But really what needs to be solved for self-replicating machines is determining a way to make actuators. On the Moon this is harder due to the difficulty of making bearings and gears. Because of vacuum welding making bearings is much more difficult. While solid lubricants do exist, it's difficult to obtain the materials necessary on the Moon. Traditional machining and polishing processes don't work well in a vacuum either due to vacuum welding and the inability to use lubricant. If we wish to carry out said processes in a pressurized environment we run into another problem: seals. In order to make good seals we need elastomers, and elastomers require elements such as hydrogen, carbon, and nitrogen which are difficult to obtain on the Moon.