Sweat rate measurement devices

A sweat sensing device capable of directly measuring sweat flow rate comprising:

• at least one flow rate sensor for measuring a sweat flow rate;
• at least one analyte sensor for measuring a characteristic of an analyte in sweat;
• and
• a microfluidic component comprising a fluid pathway for conveying at least one sweat sample into fluid communication with the at least one flow rate sensor, the at least one analyte sensor, or both the at least one flow rate sensor and the at least one analyte sensor, wherein the pathway has a first portion for collecting a sample and a second portion adjacent to the at least one flow rate sensor and the at least one analyte sensor, wherein the second portion has a volume-reduced pathway relative to the first portion;
• wherein the microfluidic component further comprises a network of closed channels in the fluid pathway, each of the closed channels in the network comprising a volume-reduced pathway and a flow rate sensor.

A method of determining sweat rate in a sweat sensing device, the method comprising the steps of:

• collecting at least one sweat sample from a portion of skin;
• drawing the sweat sample through a microfluidic component;
• measuring a flow rate of the sweat sample using at least one thermal flow rate sensor adjacent to the microfluidic component;
• measuring system noise unrelated to movement of sweat using at least one reference flow sensor;
• and
• processing the flow rate measurement and the system noise measurement to determine a sweat flow rate in the device.