Abstract Stimuli-responsive hydrogels have emerged as innovative materials for sensors and actuators, and there is a need to develop a low-cost, simple, but sensitive sensor to detect hydrogel response events to external stimuli. This paper demonstrates a fiber optic sensor platform that can detect external stimulant events of a smart hydrogel. A tapered resonant fiber sensor was fabricated using arc-induced optical fiber tapering and liquid-based gold coating on the tip of the fiber sensor. Poly N-isopropylacrylamide (pNIPAAm)-based temperature-sensitive hydrogel was selected as a model sensing material. The sensing mechanism employs the volume change of the hydrogel when the external temperature induces the phase transition of the hydrogel. To implement this concept in the proposed fiber sensor, we have developed a reliable approach to create bilayered hydrogel and elastic polymer with the tapered fiber sensor. By embedding the fiber sensor in a thin elastic polymer layer and creating a strong bonding between the hydrogel and the elastic layer through porous elastic polymer interface, the sensor operates reliably over cyclic thermal experiments. The results indicate that our sensor can detect the threshold events of the hydrogel, where its maximum volume changes occur during external temperature changes. We envisage that similar platforms can be extended to other smart hydrogels and their optical sensing applications.

中文翻译：

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用于智能水凝胶事件检测的光纤传感器平台

摘要 刺激响应水凝胶已成为传感器和执行器的创新材料，需要开发一种低成本、简单但灵敏的传感器来检测水凝胶对外部刺激的响应事件。本文展示了一种光纤传感器平台，可以检测智能水凝胶的外部刺激事件。使用电弧诱导光纤锥形和光纤传感器尖端上的液基金涂层制造锥形谐振光纤传感器。选择基于聚 N-异丙基丙烯酰胺 (pNIPAAm) 的温度敏感水凝胶作为模型传感材料。当外部温度引起水凝胶的相变时，传感机制利用水凝胶的体积变化。为了在提议的光纤传感器中实现这一概念，我们开发了一种可靠的方法来使用锥形光纤传感器创建双层水凝胶和弹性聚合物。通过将纤维传感器嵌入薄的弹性聚合物层中，并通过多孔弹性聚合物界面在水凝胶和弹性层之间建立牢固的结合，传感器在循环热实验中可靠运行。结果表明，我们的传感器可以检测水凝胶的阈值事件，在外部温度变化期间其最大体积变化发生。我们设想类似的平台可以扩展到其他智能水凝胶及其光学传感应用。通过将纤维传感器嵌入弹性聚合物薄层中，并通过多孔弹性聚合物界面在水凝胶和弹性层之间建立牢固的结合，传感器在循环热实验中可靠运行。结果表明，我们的传感器可以检测水凝胶的阈值事件，在外部温度变化期间其最大体积变化发生。我们设想类似的平台可以扩展到其他智能水凝胶及其光学传感应用。通过将纤维传感器嵌入弹性聚合物薄层中，并通过多孔弹性聚合物界面在水凝胶和弹性层之间建立牢固的结合，传感器在循环热实验中可靠运行。结果表明，我们的传感器可以检测水凝胶的阈值事件，在外部温度变化期间其最大体积变化发生。我们设想类似的平台可以扩展到其他智能水凝胶及其光学传感应用。