Described here are patches, systems, and methods for measuring glucose. In general, the patches comprise a microfluidic collection layer and a
detector, and the systems comprise a patch and a
measurement device. Some methods for measuring glucose comprise cleaning the
skin surface, collecting sweat from the
skin surface using a microfluidic collection device, and measuring the collected glucose. Other methods comprise cleaning the
skin surface, collecting sweat in a patch comprising a microfludic collection layer, and measuring glucose collected in the patch. Still other methods comprise cleaning the
skin surface, collecting a first sweat sample from the
skin surface in a patch comprising a microfludic collection layer and a
detector layer, transferring the first sweat sample from the collection layer to the
detector layer, measuring glucose in the first sweat sample, and repeating the collection, transferring, and measuring steps at least once.