Wearable sweat sensors with various sensing systems can provide noninvasive medical diagnostics and healthcare monitoring. Here, we demonstrate a wearable microfluidic nanoplasmonic sensor capable of refreshable and portable recognition fingerprint information of targeted biomarkers including urea, lactate, and pH in sweat. A miniature, thin plasmonic metasurface with homogeneous mushroom-shaped hot spots and high surface-enhanced Raman scattering (SERS) activity is designed and integrated into a microfluidics platform. Compared to conventional wearable SERS platforms with the risk of mixed effect between new and old sweat, the microfluidic SERS system allows sweat administration in a controllable and high temporal-resolution fashion, providing refreshable SERS analysis. We use a portable and customized Raman analyzer with a friendly human-machine interface for portable recognition of the spectroscopic signatures of sweat biomarkers. This study integrates epidermal microfluidics with portable SERS molecular recognition, presenting a controllable, handy, and dynamical biofluid sensing system for personalized medicine.

Wearable optical sensors have emerged as a promising technology, opening up a new way to monitor human sweat. With the advancement of integrated optical devices, optical materials, and structure design, the current optical skin interfaces primarily employ four analytical methods to transmit sweat chemical information into optical signals: colorimetry, surface-enhanced Raman spectroscopy, fluorescence, and electrochemiluminescence. To improve portability, many external laser source devices and imaging modules are upgraded based on different optical methods. Here, we summarize recent progress in optical sweat sensors, focusing on their principles, development, advantages, and limitations. Finally, current challenges and future prospects of wearable optical sensors in materials, sweat collection, data analysis, and external integrated electronics are discussed.