Light-Driven, Phase-Locked Protein Pumping Through a Single Plasmonic Optofluidic Nanopore

Dynamic protein transport through solid-state nanopores is fundamentally limited at low analyte concentrations by thick electrical double layers (EDLs) and weak electrophoretic forces. Here, a light-driven, phase-locked protein pumping mechanism is demonstrated through a ∼20 nm plasmonic nanopore embedded in an ultrathin (In_xGa_1-x)₂O₃ membrane and decorated with self-assembled Ag nanodomains. Under 488-530 nm excitation, broadband plasmonic resonances (2.3-3.4 eV) generate intense near-fields and hot-carrier surface charging, increasing the interfacial EDL capacitance to ∼220 µF·cm^{- 2} and lowering the protein entry barrier from ∼20 to <3 kBT. A combined static-dynamic fluorescence reconstruction approach resolves field-directed transport of FITC-labeled bovine serum albumin beyond the diffraction limit. Optical maps reveal a concentration-dependent transition from Brownian diffusion to a vertically extended photo-EDL conduction column that funnels proteins toward the nanopore. Simultaneous fluorescence-ionic measurements identify an electro-optic resonance within the 5-20 Hz modulation window, producing ∼10× fluorescence enhancement under pulsed excitation. The optical pumping event rate increases from ∼0.5-1 to ∼4-5 s^{- 1}, while the cis-trans phase delay decreases from ∼450 to <10 ms. These results establish plasmonic nanopores as programmable optofluidic pumps for dynamic, light-controlled single-molecule protein transport.