Multifunctional Photochromic Piezoionic Eutectogels Through Interfacial Nanoparticle Engineering

ABSTRACT Integrating emergent optical, ionic, mechanical, and electronic functionalities within soft materials enables autonomous electronics, intelligent robotics, and adaptive human–machine interfaces. Here, we introduce photoresponsive piezoionics in eutectogels nanocomposites (NCs) containing photochromic WO 3 nanoparticles (NPs). WO 3 NPs are dispersed within a photocurable deep eutectic solvent (DES) and incorporated into the crosslinked polymer network, yielding transparent, mechanically compliant, and printable eutectogel NCs. WO 3 NPs impart reversible photochromism and restructure the local ionic microenvironment, enhancing ionic transport while preserving the bulk elastic properties of the eutectogels. The resulting NCs exhibit strong optical modulation, efficient NIR attenuation, excellent thermal insulation, and compatibility with DLP‐based 3D printing. Remarkably, the photochromic transition directly modulates the piezoionic response by coupling photoinduced electronic processes with pressure‐driven ionic transport. The eutectogel containing the highest WO 3 loading generates piezoionic outputs of 52 mV and 8200 nA and 53 mV and 11000 nA in the transparent and photoactivated states, respectively. The piezoionic eutectogel NCs enable self‐powered strain sensing for soft robotics applications and optical modulation for adaptive smart windows. This work establishes interfacial nanoparticle engineering as an effective approach to coupling optical, ionic, mechanical, and electronic functionalities in eutectogels and introduces photoresponsive piezoionics as a new paradigm for self‐powered iontronics.