Wearable Sensors and Systems for Wound Healing-Related pH and Temperature Detection

Abstract

Wound healing is a complex tissue regeneration process involving many changes in multiple physiological parameters. The pH and temperature of a wound site have long been recognized as important biomarkers for assessing wound healing status. For effective wound management, wound dressings integrated with wearable sensors and systems used for continuous monitoring of pH and temperature have received much attention in recent years. Herein, recent advances in the development of wearable pH and temperature sensors and systems based on different sensing mechanisms for wound status monitoring and treatment are comprehensively summarized. Challenges in the areas of sensing performance, infection identification threshold, large-area 3-dimensional detection, and long-term reliable monitoring in current wearable sensors/systems and emerging solutions are emphasized, providing critical insights into the development of wearable sensors and systems for wound healing monitoring and management.

Keywords: pH; smart systems; temperature; wearable sensor; wound management.

Figure 6

(a) Schematic illustration of the fabrication process of Gr/SF/Ca²⁺ E-tattoo and relative resistance changes of pristine and healed temperature sensors (Reprinted with permission from [89]). (b) The fabrication and temperature sensing performance of flexible and breathable on-skin devices featuring temperature triggered drug release ability (Reprinted with permission from [99]). (c) Schematic illustration of the structures and working principles of the smart wound dressing integrated with flexible electronics and UV-triggered drug release: (i) real-time monitoring of wound temperature; (ii) turning on UV light to trigger the drug release; (iii) infection inhibition, resulting in a decreased wound temperature; (d) In vivo studies of the smart wound dressing on infection monitoring and timely treatment: (i) wound creation; (ii) implantation of smart system; (iii) pressure dressing; (iv) real-time temperature monitoring. (Reprinted from [101]).

Figure 1

Wearable sensors/systems for wound related biomarkers (e.g., pH, temperature) detection to monitor wound healing status.

Figure 2

Changes in pH during different wound status and importance of managing pH in chronic wound. (Reprinted from [33]).

Figure 3

(a) Schematic illustration of alginate-based hydrogel microfibers loaded with pH-responsive beads (i) and the action mechanism of solid matrix of the mesoporous particles (ii); (b) the wound dressings fabricated by hydrogel microfibers response to different pH (Reprinted with permission from [51]); (c) synthesis of orange-emissive carbon quantum dots (O-CDs); (d) comparison of photoluminescence intensities of O-CDs on medical cotton cloth (MCC) before and after immersion in phosphate-buffered saline (PBS) buffers with different pH (Reprinted with permission from [52]); (e) fabrication process of curcumin-loaded fibers used for wound pH detection; (f) RGB (red, green, blue) values of polymer fibers after pH detection were determined by smartphone (Reprinted with permission from [36]).

Figure 4

(a) Optical images of conductive thread-based pH sensor array; (b) mechanism of microfluidic pH sensor in skin wound pH detection; (c) the thread-based pH sensor passed through a normal needle; images of the thread-based pH sensor used for (d) stomach and (e) subcutaneous pH sensing (Reprinted from [58]).

Figure 5

(a) Schematic illustration of colorimetric responsibility of optical temperature sensor based on thermochromic liquid crystal (CTL); (b) optical image of the sensing unit of wearable temperature sensor at different temperatures (Reprinted with permission from [85]); (c) the fabrication process of thermochromic membrane containing TC-M/NPCMs; (d) colorimetric response and application of the colorimetric temperature sensor; (e) applications of temperature colorimeter in different positions of body surface. (Reprinted with permission from [86]).