Nature Mater. http://doi.org/ksw (2013)

Credit: © 2013 NPG

Stacking two-dimensional circuits to form three-dimensional arrays of interconnected chips may seem like the ultimate solution to our ever-increasing demands for high-performance microelectronic devices. But engineering the electrical connections between wafers is no mean feat, and at present prototypical devices face severe limitations associated with the precision of assembly. It seems now, however, that using naturally self-organizing materials might be a way forward. Rémi Galland and colleagues have succeeded in controlling the growth of actin filament networks — the building blocks of the cellular cytoskeleton — to form conductive connections between chips.

By micropatterning chips with an actin-promoting factor, and then flooding them with an actin polymerization mix, the authors were able to induce the localized growth of actin networks on the surface, but failed to control their three-dimensional architecture. This problem was solved with the introduction of capping proteins, which promote the branching of actin filaments by blocking elongation. The force generated by actin filament assembly effectively displaced the assembled network upwards, replicating the micropatterned network in a series of layers that made contact with a second surface. Once formed, these organic connections were coated with gold, and proved capable of conducting electricity between chips.