Initiator integrated 3D printing, namely i3DP, was developed by incorporating a vinyl-terminated initiator into UV curable resin to make functional structural materials that enable genetic post-printing surface-initiated modification. Taking advantage of 3D printing and surface-initiated ATRP, the feasible i3DP makes 3D printed complex architectures possible for nearly any desired surface modification for various applications, for example, even pouring water into a sieve was readily achieved.