Spontaneous Interfacial Redox Enables Spatiotemporally Registered Visual‐Tactile Interfaces

ABSTRACT Visual‐tactile interfaces that provide simultaneous optical feedback and pressure mapping are hindered by mismatched ion‐electron transport timescales and electrical crosstalk in stacked devices. Here, a mechanically triggered, bias‐free electrochromic strategy is developed through spontaneous interfacial redox between an InSnBi liquid metal and a WO 3 ‐polyacrylamide hydrogel. The built‐in galvanic potential drives electron transfer and Li + intercalation at the contact interface, producing 77% of the visible color saturation within 460 ms without applying an external voltage to the display layer. This response approaches the 215 ms timescale of the underlying piezoresistive sensor. Localized coloration, together with pixel isolation and electromagnetic shielding, enables vertical integration with a 1,024‐pixel pressure array while suppressing interlayer crosstalk. A single writing event therefore yields two spatially registered yet functionally complementary outputs in the form of persistent optical trajectories and dynamic pressure distributions. Feature‐level fusion of the two channels increases handwriting‐user recognition accuracy from 88.03% for optical data and 61.81% for tactile data to 94.64%. This work establishes spontaneous interfacial redox as a materials strategy for temporally aligned and spatially registered visual‐tactile interfaces.