Bacterial surface-layer proteins for electrochemical nanofabrication

We have used electrochemical processing to fabricate ordered arrays of metals and metal oxides on surfaces at densities exceeding 1012 cm−2, on mm2 areas, and with typical feature sizes of 2–3 nm. This is achieved via masks obtained from naturally occurring proteins that assemble into two-dimensional crystals containing internal porous structure within each unit cell of the crystalline lattice. We have proven this process with bacterial cell surface proteins (S-layer proteins) from Deinococcus radiodurans and Sporosarcina ureae. Each of these S-layer proteins has unique lattice geometry and internal structure. Substrates are coated by adsorption from a dilute suspension of purified, stabilized protein extract. Electrochemical deposition proceeds through solvent accessible pores of the S-layer crystal to build surface structures with nanometer scale feature sizes and spacings precisely matching the geometry of the protein “mask”. Comparisons between the structure of the electrodeposited material through the protein mask and the protein surface topography suggest that the S-layers of D. radiodurans possess pores providing straight through-holes to the surface, whereas the S-layers of S. ureae presents a more tortuous pathway to the electrode surface.