Embedded microstrip antenna
These antenna design are IP(Intellectual property) of an oraganisation used in Semi-custom development,developing a patch antenna can be done easily,but doing it as an separate entity I guess can be done using a 3D printer.

You can build you Full Custom design, the main elements are the maintenance of the fringe-fields across the dielectric-ground plate and dielectric-patch boundary, you must apply boundary condition to check the radiation pattern and its range.


I would suggest you read Microstrip Antenna Design Handbook
 By Ramesh Garg.
Some document specifying the many other circuits production using 3D print are given here.
See page 123 gives you all possible dimensions of the Patch now you have to design a radiating driver circuit.Best of Luck.