Prior to 1970, bulletproof vests were pretty iffy, with a history extending as far as the 1500s when there were attempts to make metal armor that was bulletproof.
By the 20th century there was ballistic nylon, but it took Kevlar to produce garments with real protection against projectile impact. Now a 3D printed nanomaterial might replace kevlar.
A group of scientists have published a paper that interconnected tetrakaidecahedrons made up of carbon struts that are arranged via two-photon lithography.
We know that tetrakaidecahedrons sound like a modern invention, but, in fact, they were proposed by Lord Kelvin in the 19th century as a shape that would allow things to be packed together with minimum surface area. Sometimes known as a Kelvin cell, the shape is used to model foam, among other things.
The 3D printing, in this case, is a form of lithography using precise lasers, so you probably won’t be making any of this on your Ender 3. However, the shape might have some other uses when applied to conventional 3D printing methods.