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

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-Fe 3 O 4 strips in porous agarose (MMFPA), which exhibits enhanced permeability and speeding diffusion of electrolyte ions. Moreover, the orientation in order and strip-like MWCNT-Fe 3 O 4 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 protocol is successfully utilized to monitor Cd 2+ trace residues in rice, tea, and soil with an affordable response as low as 0.112 mg/kg and rapid signal acquisition (<5 min). It paves an attractive, accessible, and effective way to on-site evaluate solidoid Cd 2+ level for forewarning food safety and environmental risk.