Microcapsule‐Based Visualization Smart Sensors for Damage Detection: Principles and Applications

Abstract

The smart sensor is an effective way to detect damage and improve structural safety in structural health monitoring. Microcapsule‐based visualization sensors stand out from the smart sensors. Here, the research progress of microcapsule visualization materials in recent years is summarized and the sensing principles, influence factors, performances, applications, and future prospects are introduced. The way to achieve the visualizing function of microcapsule visualization sensors is the fabrication of microcapsules that are encapsulated with solutions of dyes or indicator. When the protective shell of microcapsules is broken, the dyes will be released and activated under optical, chemical, or mechanical conditions. These visualized microcapsules can be added to the interior of the structure or prepared as a coating to provide structural health monitoring of the interior and surface of the structure. They can accurately detect microcracks and highlight them in bright colors. Additionally, the structural health monitoring applications of microcapsule visualization sensing coatings in concrete, asphalt, and steel are presented with detailed examples. The development and application of these microcapsule visualization sensors are of great significance in improving the structural life and avoiding structural failure in engineering.

Vorbeugen oder Heilen – die beispiellose Notwendigkeit von selbstberichtenden Materialien

“…Tatsächlich sind verschiedene Te chniken entwickelt worden, um mechanisch bedingte Schäden auf selbstberichtende Weise anzuzeigen. Diese Te chniken basieren im Allgemeinen auf dem Einbau von mit Farbstoff gefüllten Kapseln, [24,[29][30][31][32][33][34] Mechanophoren, [35][36] Fasern [23,37,38] oder Sensormolekülen [39][40][41] in Verbundstoffe,P olymermatrices/-netzwerke/-hydrogele (siehe Schema 1) mit der Absicht, die Nervensysteme und Gewebe biologischer Organismen nachzuahmen. Bei mechanischer Beschädigung werden die selbstberichtenden Eigenschaften ausgelçst und durch Fluoreszenz-, Lumineszenz-oder Farbänderungen visualisiert.…”

Microcapsule encapsulated with leuco dye as a visual sensor for concrete damage indicationviacolor variation

“…A series of visual damage strategies based on visualization materials had been developed for damage indication. [10][11][12][13][14] Dye-lled hollow glass ber [15][16][17] was used to indicate mechanic damages for polymers, but it cannot be applied to the surfaces of complex structures because of its slender shape. The microcapsule-based visualization sensor solves these problems better.…”

Fabrication of microcapsule-type composites with the capability of underwater self-healing and damage visualization

“…The property of self-healing plays an important role in improving the safety of structures and extending their service life, especially in applications such as underground pipeline transportation and marine engineering. 1,2 Moreover, cracks tend to occur in dark environments and are difficult to view. Therefore, it is crucial to detect and repair any damage in advance to protect materials.…”