Hydrophobic Eutectogels Reinforced by Zn²⁺-Coordinated Lignin Nanoparticles for Underwater Wearable Electronics

Wearable flexible sensors for underwater communication and biomotion monitoring are gaining attention. However, developing gel-based strain sensors with high toughness, anti-swelling performance, robust underwater adhesion, and long-term stability remains challenging. Herein, we present a hydrophobic eutectogel (DPF-Zn@LNP-HEG) fabricated via the assembly of a polymerizable hydrophobic deep eutectic solvent (PHDES), 2-phenoxyethyl acrylate (PEA), and Zn²⁺-coordinated lignin nanoparticles (Zn@LNP). The resulting structure, composed of hydrophobic polymer networks and metal-phenolic complexes, forms hydrophobic microdomains that disrupt the hydration layer and prevent water penetration. Meanwhile, Zn@LNP serve as dynamic sacrificial cross-linkers, enhancing the material's mechanical strength, energy dissipation, and anti-swelling properties. The resulting eutectogel exhibits remarkable tensile strength (1.14 MPa), superior toughness (3.15 MJ m^-3), excellent anti-swelling properties (< 1% after 30 days), and robust underwater adhesion (1.07 MPa on glass). Based on these properties, we demonstrate an underwater strain sensor with high sensitivity (gauge factor = 8.12) and long-term stability, enabling underwater Morse code transmission, biomotion monitoring, and Bluetooth-based tracking of swimming movements. This work not only provides a versatile design paradigm for multifunctional underwater sensing platforms but also advances the high-value utilization of bio-based materials in next-generation flexible electronics.