Polyanionic copolymer-enhanced eutectogels with high toughness, strain sensitivity and electromagnetic wave absorption for multifunctional strain/pressure sensor

Integrating flexible sensors into miniaturized electronic devices requires them to meet stringent performance criteria, namely the ability to suppress electromagnetic interference through effective microwave absorption while also exhibiting high sensitivity to mechanical strain. Herein, we prepared sodium alginate (SA)-enhanced deep eutectic solvent-based (DES-SA) dual-network eutectogels with high-density hydrogen bonds (HB) network by interpenetrating the rigid chains of SA with deep eutectic components. On the one hand, the dynamic sacrificial and recombination of HB significantly optimizes the toughness of DES-SA gels, achieving a 7300% improvement compared to the unmodified gel (DES-0.5). Since strain-induced resistivity changes are governed by synergistic modulation of electrostatic interaction between carboxylate anions (-COO⁻) and choline cations and the size effect of the ionic transport channels, the highly conductive DES-SA gels exhibit a gauge factor of 3.00, representing a 250% increase compared to DES-0.5. On the other hand, the numerous polar groups (-OH, -COO⁻ within DES-SA gels induce dipole relaxation loss under alternating electromagnetic field, resulting in effective absorption bandwidths that cover the entire X-band and Ku-band at thicknesses of 1.80 mm and 2.30 mm, respectively. This work presents a versatile eutectogel that concurrently fulfills the critical requirements for next-generation flexible sensors, integrating exceptional toughness, high strain sensitivity, and broad-band microwave absorption into a single material system.