**4. Future**

pH value is one of the most important factors affecting physiological performance. It may be very useful for making diagnoses and for monitoring and treating wounds and skin-related diseases. pH influences skin barrier functions and plays a critical role in regulating the activation of proteases related to wound healing processes and the development of chronic wounds. Furthermore, it has been correlated with bacterial enterotoxin activity and antibacterial efficacy. Monitoring pH changes in wound regions is a fast and simple method for monitoring wound healing processes and preventing the formation of chronic wounds. Developing a smart bandage equipped with a pH sensor or other systems (e.g., drug control-released carriers) have become increasingly popular in recent years. Besides, tools for non-invasive diagnosis and therapy monitoring in dermatology (e.g., raster-scan optoacoustic mesoscopy (RSOM) and in vivo reflectance confocal microscopy (IVCM)) have also been introduced [105,106]. They are expected to promote additional tools and processes to promote wound healing. While pH value is a simple physiological concept, it could promote a significantly positive impact on not only clinically relevant diagnoses but personal health managemen<sup>t</sup> in the home.

**Author Contributions:** Conceptualization, S.-H.K., C.-M.C.; formal analysis, S.-H.K.; writing—original draft preparation, S.-H.K.; writing—review and editing, S.-H.K., C.-M.C., C.-J.S., C.-F.S.; visualization, S.-H.K.; supervision, C.-M.C., C.-J.S., C.-F.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** The research was funded by the Ministry of Science and Technology, Taiwan (MOST 108-2745-8-007-001 & 109-2623-E-007-002-D).

**Acknowledgments:** We thank our colleagues who provided insight and expertise that greatly assisted this review.

**Conflicts of Interest:** The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
