A method for sensing the electrolytic conductivity of a fluid, the method comprising: - providing a battery comprising an oxidizing electrode and a reducing electrode separated at a distance and connected by a hydrophilic and/or a porous material or an empty receptacle providing a microfluidic cavity, wherein the battery is sensitive, only, to the presence of analytes with ionic charge that determine an electrolytic conductivity of a fluid to be sensed, the fluid acting as battery electrolyte and not as a fuel, wherein the oxidizing and reducing electrodes are connected through the fluid, wherein an internal resistance of the battery depends on said electrolytic conductivity of the fluid, and wherein the battery is activated upon the addition of said fluid to said microfluidic cavity or said hydrophilic and/or porous material; - providing, by the battery, electrical energy while the fluid impregnates by capillarity the microfluidic cavity or said hydrophilic and/or porous material; and - connecting at least one instrument to the battery, wherein said instrument is designed such that its equivalent impedance makes the battery work at a specific operating point that allows determining the electrolytic conductivity of the fluid via a Direct Current, DC, mode method, and wherein the instrument quantifies said electrolytic conductivity of the fluid from the electrical energy supplied by the battery, such that the electrolytic conductivity of the fluid is inferred from the performance of the battery. - providing a battery comprising an oxidizing electrode and a reducing electrode separated at a distance and connected by a hydrophilic and/or a porous material or an empty receptacle providing a microfluidic cavity, wherein the battery is sensitive, only, to the presence of analytes with ionic charge that determine an electrolytic conductivity of a fluid to be sensed, the fluid acting as battery electrolyte and not as a fuel, wherein the oxidizing and reducing electrodes are connected through the fluid, wherein an internal resistance of the battery depends on said electrolytic conductivity of the fluid, and wherein the battery is activated upon the addition of said fluid to said microfluidic cavity or said hydrophilic and/or porous material; wherein the battery is sensitive, only, to the presence of analytes with ionic charge that determine an electrolytic conductivity of a fluid to be sensed, the fluid acting as battery electrolyte and not as a fuel, wherein the oxidizing and reducing electrodes are connected through the fluid, wherein an internal resistance of the battery depends on said electrolytic conductivity of the fluid, and wherein the battery is activated upon the addition of said fluid to said microfluidic cavity or said hydrophilic and/or porous material; - providing, by the battery, electrical energy while the fluid impregnates by capillarity the microfluidic cavity or said hydrophilic and/or porous material; and - connecting at least one instrument to the battery, wherein said instrument is designed such that its equivalent impedance makes the battery work at a specific operating point that allows determining the electrolytic conductivity of the fluid via a Direct Current, DC, mode method, and wherein the instrument quantifies said electrolytic conductivity of the fluid from the electrical energy supplied by the battery, such that the electrolytic conductivity of the fluid is inferred from the performance of the battery.