In short I'm looking at creating an artificial sperm smart enough to fertilize an egg and develop into an embryo, so that would mean the sperm must have some means of carrying information similar to DNA and interact with it. I think of it as a parasite scavenging for necessary material from the egg and transform the egg into an embryo capable of developing into a design baby, am I being naïve or that's just scratching the surface using science? btw everything is customizable so you can set the skin pigmentation, hair color, pupil color, quintuplets, conjoins, you get the drift.
Some times ago there have been reports of synthetic sperm cells being created
Experiments with mice show that synthetic sperm and eggs can be created using stem cell technology.
Just get the right proteins on the surface, so that the egg will be lured into letting the bot in, and have the correct DNA available to trigger cellular multiplication.
Simpler than creating a nanobot is to take existing sperm cells, remove their original DNA and replace it with DNA which contains the predesigned genetic information at the position of the respective gene loci. This is more or less feasible with existing technology in molecular biology (as L.Dutch already pointed out) - the main problem being that it is cost intensive and that cutting the DNA in all the right spots and placing all the predesigned genes in exactly the correct places is a tough challenge. An even if all this works out correctly, during the mitotic process when reuniting the two halves of DNA into a full organism's DNA and reproducing it many times to create an embryo still underlies the typical biological chance of mistakes in the repoduction.
Also by controlling the sperm you do not control the majority of information inherited by the embryo. You cannot control the inforation inherited from the motherly DNA. Some traits have a dominant inheritance meaning that the DNA from one of the genes would always overrule the information of the other. Also, mitochondria - formerly bacteria, now cell organella repsonsible for producing the cell's energy for living and 'working' - contain their own DNA and are only inherited from the egg cell.