Sweat conductivity, volumetric sweat rate, and galvanic skin response devices and applications

A sweat sensing device configured to be worn on a wearer's skin, comprising:

• a sweat collector having a sealing component, where the collector has sufficient clearance from the skin to promote natural flow of sweat, and has a skin coverage area within the collector that is determined, and where the sealing component is configured to substantially prevent sweat and surface contaminants from entering the coverage area from skin located outside the coverage area;
• a microfluidic channel for receiving and transporting a sweat sample, where the channel has an inlet at a first end, an outlet at a second end, and has a known volume;
• a plurality of electrodes for measuring galvanic skin response, where said GSR electrodes are configured to contact the wearer's skin when the device is being worn;
• a plurality of electrodes for measuring sweat conductivity, where said conductivity electrodes are in fluid communication with said channel;
• and
• a volumetric sweat rate sensor, where the volumetric sensor includes a detection circuit that includes a plurality of electrodes, where said electrodes intersect said channel at known intervals, where said electrodes are in fluid communication with the channel, and where said electrodes divide the channel into a plurality of channel sections.