Synthesis and properties of SiO/SiO@Ag two-phase STFs.

Soft body armor with a strain-sensing function using conductive shear thickening fluids (STFs) has gradually gained research interest. In this study, conductive SiO@Ag core-shell microspheres were synthesized and the influence of process parameters on their properties was evaluated. Subsequently, SiO and SiO@Ag were used as dispersed phases to prepare two-phase STFs, the effect of the core-shell microspheres' proportion on the rheological properties of the STFs was investigated, and its mechanism was discussed. The results indicated that SiO@Ag core-shell microspheres were coated with elemental silver and when the concentration of sodium hydroxide and glucose were 0.07 and 0.09 mol L, respectively, the coating surface was the most uniform and compact, and the conductivity reached the minimum value of 0.56 Ω cm. The two-phase STFs exhibited good and reversible shear thickening behaviors and the critical shear rate decreased with increasing core-shell microsphere concentration. Additionally, when the mass fraction of SiO and SiO@Ag core-shell microspheres was 45% and 20%, respectively, the thickening rate was 325%, and the resistance of two-phase STFs decreased simultaneously with the emergence of shear thickening that reached the lowest value of 795.16 kΩ. This study provides a novel strategy for synthesizing conductive STFs for strain-sensing flexible stab-resistant composites.