A nanoconfined liquid-in-ice aqueous regime for time-stretched single-molecule dynamics

The experimentally observable dynamical landscape of biomolecules is fundamentally shaped by rapid thermal motions of the surrounding aqueous environment. Although lowering temperature could expand this observable landscape, the liquid-solid phase transition of water has long prevented real-time single-molecule measurements into deeply subzero aqueous environments. Here we show that nanoconfinement within a solid-state nanopore overcomes the fundamental limitation imposed by bulk water freezing, spontaneously stabilizing a persistent liquid-in-ice environment that remains electrically accessible despite surrounding electrolyte crystallization. This aqueous environment creates a time-stretched dynamical regime, extending molecular translocation timescales by up to ~400-fold and revealing previously inaccessible single-molecule dynamics. These findings establish a new low-temperature aqueous regime for real-time single-molecule measurements, opening new opportunities to investigate biomolecular dynamics across previously inaccessible timescales and extreme aqueous environments.