Magnetically-oriented porous hydrogel advances wearable electrochemical solidoid sensing heavy metallic ions

This work reports that the magnetically oriented porous hydrogel installed on the glove sensor is first time constructed as a wearable solidoid sensing platform for on-site chemical contamination evaluation. Such hydrogels with uniform porous distribution and highly tunable anisotropic MWCNT-Fe3O4 strips act as the electrochemical cell and medium of analyte diffusion to enhance the permeability and effectively speed electrolyte ion diffusion. The MWCNT-Fe3O4 strips doped in the three-dimensional rigid hydrogel exhibit a quick recovery from compressive strength within 2 min. The hydrogel could be easily and tightly assembled onto the wearable glove sensor by using a magnet, improving the stability and sensitivity of the sensing platform. The wearable glove sensor is successfully applied for rapid detection (< 5 min) of trace Cd2+ in tea, rice, and soil. [Display omitted] •Magnetically oriented hydrogel is prepared to realize wearable electrochemical solid sensing.•Magnetic porous hydrogel has excellent conductivity and mechanical performance.•The wearable sensing platform is used to monitor Cd2+ in tea, soil, and rice powder.•Swipe sampling method is introduced to pretreat the solid samples on-field. Developing wearable sensors to determine chemical contamination in solidoid is currently a great challenge. Hydrogels with polymeric networks have been employed as electrochemical cells and media to realize wearable solidoid sensing. However, it is still a hard task to enable hydrogel to simultaneously possess effective mass transfer, mechanical robustness as well as easy and tight adhesion to sensing electrodes. Routinely, a hydrogel with improved adhesion to the electrode surface by introducing additives may deteriorate the mass transfer capability. Increasing the porosity of hydrogel could enhance mass diffusion but sacrifices mechanical robustness. Herein, a composite hydrogel is achieved by embedding magnetic oriented MWCNT-Fe3O4 strips in porous agarose (MMFPA), which exhibits enhanced permeability and speeding diffusion of electrolyte ions. Moreover, the orientation in order and strip-like MWCNT-Fe3O4 three-dimensional composites improve the compressive strength of hydrogel, which could recover back within 2 min in water after removal of pressure. Such magnetic hydrogel is beneficial to be assembled to the wearable glove sensor by using magnets to achieve a stable and compact sensing platform. As the application example, the resultant wearable sensing pr