Hard-wired Solid-state Bioelectronic Micropore Devices: Permanent Metal-Protein-Metal Junction Proof-of-Concept

We present the design, fabrication, and application of robust metal/protein/metal junctions with ultrathin (~20 nm) protein films demonstrating long-term stability in ambient conditions and preserving their electron transport behavior also at ~10 K. These junctions establish a reliable platform with a permanent contact configuration, where the confined protein layer retains its functional activity after metal contact evaporation on the protein. A bottom-up micropore device (MpD) fabrication strategy was used and optimized to ensure reproducibility. The sub-nanometer roughness of the bottom electrode was preserved within the micropore, enabling uniform protein layer deposition and film formation. In the MpD structures, protein layers are integrated between Au-covered substrates and an e-beam evaporated Pd contacts. Depositing multi-layered protein films allows for defining film widths, as tested by the AFM-based scratching technique. The films were composed of human serum albumin (HSA) and bacteriorhodopsin (bR). Pd’s preferred two-dimensional growth minimized metal penetration and short circuits. Impedance phase response analysis shows that ~60% of the junctions are functional ones, demonstrating the effectiveness of the fabrication approach. These protein-based MpD junctions provide a stable platform for electron transport studies of bio- and other soft materials.