Potassium (K

+

) and sodium (Na

+

) ions are essential electrolytes in body fluids. Their concentration variations provide crucial indicators to evaluate hydration status

electrolyte homeostasis

and the diagnosis related diseases. Flexible dual sensors are fabricated on a flexible polyethylene terephthalate (PET) substrate by stencil printing of multi-walled carbon nanotubes (MWCNTs) as the conductive layer

followed by modification with different functional layers to achieve lightweight and integrated multi-parameter monitoring. The developed K

+

and Na

+

sensors

exhibit near-Nernstian response sensitivities of 95.69mV/dec and 87.6mV/dec

respectively

across the physiologically relevant concentration range of 1 to 160mmol/L

with linear correlation coefficients greater than 0.98. The stability

reproducibility

and selectivity of the sensor are tested in this paper. These results provide an effective device foundation for developing flexible electrolyte sensors applied to wearable health monitoring.