This invention discloses a sensor for measuring parameters of sweat from a skin, comprising a flexible structure comprising a fluid passage having inlet and outlet, the flexible structure being detachably attached to the skin and configured such that sweat enters the inlet as the sweat releases from the skin and flows through the fluid passage into the outlet; a thermal actuator disposed on the flexible structure over the fluid passage and configured to operably provide heat to flow of the sweat through the fluid passage; a first thermistor disposed on the flexible structure over the fluid passage between the inlet and the thermal actuator and configured to operably measure a first temperature of the sweat thereon; and a second thermistor disposed on the flexible structure over the fluid passage between the thermal actuator and the outlet and configured to operably measure a second temperature of the sweat thereon.