Contrary to a popularly held belief, it may well be about the surface of things and not what's inside.

A group of scientists, led by Xiaolong Wang at the Chinese Academy of Sciences and Jun Yang's team at the University of Western Ontario, have developed an approach which allows them to 3D print modular surfaces and thereby obviate the need for multiple 3D printers.

This versatile 3D printing process, which uses a bromine acrylate added to 3D printing resin, allows the acrylate to act as a spur for polymer brushes to "grow" on a printed surface.

They're calling it, "initiator integrated 3D printing" or "i3DP," and the process includes a vinyl-terminated initiator in UV curable resin to make functional structural materials which allow for genetic post-printing modifications.

They say "i3DP" makes 3D printing complex architectures possible for "nearly any desired surface modification for various applications."

As a test of their integrated printing method, the team fabricated lattices containing the polymer brushes, and then modified them to either act as superhydrophobic or superhydrophilic structures.

A cubic superhydrophobic lattice managed to repel a water droplet, and a superhydrophobic, hollow mesh ball with 1 mm pores contained fluid without leaking, even as it was shaken.

"The printed mesh ball held the water completely," said Wang. "There's a Chinese proverb that says 'pouring water into a sieve gets you nothing,' but now we've developed a way to make whatever functional complex structures we want. Even a sieve that can hold water."

The team are working on printing smaller structures with greater accuracy using different materials and processes.