LAUSR

DOI: 10.1002/aelm.202000721 lacks native conductivity to be the active conductive element in a conventional sensor structure. In contrast, the electrically conductive protein nanowires (e-PNs) harvested from the microbe Geobacter sulfurreducens are intrinsically conductive.[12,13] e-PN conductivity can be tuned with genetic modifications to yield a range of conductivities (≈10 μS cm−1 to 1 kS cm−1) in thin (≈3 nm) wires.[12,13] e-PN conductivity is highly responsive to pH, with changes of 5000-fold in individual wire conductivity over a range of pH 2–10.5.[14] These results demonstrate that e-PN conductivity is highly sensitive to changes in surface charge state, a desirable feature for designing sensing capabilities because surface adsorbates often induce a change in surface charge.[15,16] Although they are comprised of protein, G. sulfurreducens e-PNs are highly robust with stability over a broad pH range (e.g., pH 2–10), at high temperatures (>100 °C) and in organic solvents.[12] Unlike silicon nanowires,[17,18] e-PNs do not dissolve in physiological fluids. e-PNs can be mass-produced from inexpensive renewable feedstocks without the need for hazardous chemicals in processing and there are no toxic components in the final product.[12,13] They are fabricated from renewable feedstocks, with energy requirements 100-fold less than for processing silicon.[19] Thus, e-PNs are a “green” electronic material, with the low-cost, low-energy, and low-waste properties desirable for many dispensable wearable devices.