Epidermal Patch with Biomimetic Multistructural Microfluidic Channels for Timeliness Monitoring of Sweat.

Wearable sweat sensors have been developed rapidly in recent years due to the great potential in health monitoring. Developing a convenient manufacturing process and a novel structure to realize timeliness and continuous monitoring of sweat is crucial for the practical application of sweat sensors. Herein, inspired by the striped grooves and granular structures of bamboo leaves, we realized an epidermal patch with biomimetic multilevel structural microfluidic channels for timeliness monitoring of sweat via 3D printing and femtosecond laser processing. The striped grooves and ridges are alternately arranged at the bottom of the microfluidic channels, and the surface of the ridges has rough granular structures. The striped grooves improve the capillary effect in the microchannels by dividing the microchannels, and the granular structures enhance the slip effect of sweat by increasing surface hydrophobicity. The experimental results show that compared with the conventional microfluidic channels, the water collecting rate of the biomimetic microchannels increased by about 60%, which is consistent with the theoretical analysis. The superior sweat-collecting efficiency in the epidermal patch with the biomimetic multistructure enables sensitive, continuous, and stable monitoring of sweat physiological signals. Besides, this work provides new design and manufacturing approaches for other microfluidic applications.