Abstract: Some implementations of the disclosure relate to a wearable biosensor device including: a microfluidic module configured to collect a sweat sample from skin of a user, route the sweat sample to a sensing reservoir that is filled with the sweat sample, and route additional sweat away from the sensing reservoir when the sensing reservoir is filled; and a sensor assembly configured to quantify the biomarker of the sweat sample in the sensing reservoir to determine a concentration of the biomarker present in the sweat sample. The sensor assembly includes a biorecognition interface having a surface functionalized with an aptamer that binds to the biomarker.