LAUSR

Blood sampling is a common practice to monitor health, but it entails a series of drawbacks for patients including pain and discomfort. Thus, there is a demand for more convenient ways to obtain samples. Modern analytical techniques enable monitoring of multiple bioanalytes in smaller samples, opening possibilities for new matrices, and microsampling technologies to be adopted. Interstitial fluid (ISF) is an attractive alternative matrix that shows good correlation with plasma concentration dynamics for several analytes and can be sampled in a minimally invasive and painless manner from the skin at the point‐of‐care. However, there is currently a lack of sampling devices compatible with clinical translation. Here, to tackle state‐of‐the‐art limitations, a cost‐effective and compact single‐microneedle‐based device designed to painlessly collect precisely 1.1 µL of dermal ISF within minutes is presented. The fluid is volume‐metered, dried, and stably stored into analytical‐grade paper within the microfluidic device. The obtained sample can be mailed to a laboratory, quantitatively analyzed, and provide molecular insights comparable to blood testing. In a human study, the possibility to monitor various classes of molecular analytes is demonstrated in ISF microsamples, including caffeine, hundreds of proteins, and SARS‐CoV‐2 antibodies, some being detected in ISF for the first time.