Alexander Bolonkin has proposed the possibility of manipulating nucleons to produce stable, macroscopic structures of nuclear matter at zero pressure (which he calls "AB-matter"), by analogy with the nanotech ideas of directly manipulating atoms to build high-tech materials.
The basic claim is that an unbounded number of alternating protons and neutrons can be arranged in a fiber held together by residual nuclear force and a small contribution from magnetism due to the nucleon magnetic moments, and prevented from collapsing and held rigid by electrostatic repulsion. Superstrong macroscopic structures can then be built by combining these basic nuclear matter needles.
Bolonkin is a legitimate scientist (PhD in aerospace engineering), but not a nuclear physicist, and has gotten papers on this stuff published, but not in physics journals (for example, "Femtotechnology: Nuclear AB-Matter with Fantastic Properties" in American Journal of Engineering and Applied Sciences and "Femtotechnology: Design of the Strongest AB Matter for Aerospace" in Journal of Aerospace Engineering). Furthermore, nobody else seems to have published anything on this topic, all of which makes me rather skeptical of his claims.
So, ignoring the issue of how you'd construct it in the first place (assume we find some helpful Cheela to do it for us or something), could a linear arrangement of alternating protons and neutrons at zero pressure (i.e., not confined in a neutron star or something) remain stable and not collapse into one big nucleus, or segment itself into a bunch of individual nucleii? And does it make any difference if the fiber is kept under tension by some external means?