Figure 3.

(a) Top: A wireless capacitive/colorimetric sensor designed to be attached to the skin. It can be seen how Cu²⁺ accesses the sensing zone. Bottom: Change of color at different pH levels in sweat. Adapted from ref (64). Copyright 2014 John Wiley and Sons. (b) Left: Modification of the paper substrate to obtain glucose and lactate sweat sensors. Right: On-body tests using the paper-based wearable sensors. Adapted from ref (65). Copyright 2021 Elsevier. (c) Left: Sweat output pathways of the human body covered with the hydrophobic/hydrophilic textile. Right: Conical micropores across the textile designed to transport sweat by asymmetric curvature. Reproduced with permission from ref (72). Copyright 2019 John Wiley and Sons. (d) Left: A sensing band worn on the subject’s skin. Right: Cross-sectional view of sweat pumped from subcutaneous sweat glands and precisely attracted onto indicator-modified superhydrophilic microwells for colorimetric cetection. Reproduced from ref (73). Copyright 2019 American Chemical Society.