Dong Qian, Bae Hyungdae, Zhang Zhijian, Chen Yongyao, Wen Zhongshan, Olson Douglas A, Yu Miao, Liu Haijun
Department of Mechanical Engineering, Temple University, Philadelphia, PA 19122.
Department of Mechanical Engineering, Howard University, Washington, DC 20059.
J Vib Acoust. 2019;141. doi: 10.1115/1.4042929.
Graphene has been known to possess exceptional mechanical properties, including its extremely high Young's modulus and atomic layer thickness. Although there are several reported fiber optic pressure sensors using graphene film, a key question that is not well understood is how the suspended graphene film interacts with the backing air cavity and affects the sensor performance. Based on our previous analytical model, we will show that the sensor performance suffers due to the significantly reduced mechanical sensitivity by the backing cavity. To remedy this limitation, we will, through experimental and numerical methods, investigate two approaches to enhance the sensitivity of fiber optic acoustic pressure sensors using graphene film. First, a graphene-silver composite diaphragm is used to enhance the optical sensitivity by increasing the reflectivity. Compared with a sensor with pure graphene diaphragm, graphene-silver composite can enhance the sensitivity by threefold, while the mechanical sensitivity is largely unchanged. Second, a fiber optic sensor is developed with enlarged backing air volume through the gap between an optical fiber and a silica capillary tube. Experimental results show that the mechanical sensitivity is increased by 10× from the case where the gap side space is filled. For both approaches, signal-to-noise ratio (SNR) is improved due to the enhanced sensitivity, and COMSOL Thermoviscous acoustics simulation compares well with the experimental results. This study is expected to not only enhance the understanding of fluid-structural interaction in sensor design but also benefit various applications requiring high-performance miniature acoustic sensors.
众所周知，石墨烯具有优异的机械性能，包括极高的杨氏模量和原子层厚度。尽管已有多篇报道使用石墨烯薄膜的光纤压力传感器，但一个尚未得到很好理解的关键问题是，悬浮的石墨烯薄膜如何与背衬空气腔相互作用并影响传感器性能。基于我们之前的分析模型，我们将表明，由于背衬腔导致机械灵敏度显著降低，传感器性能会受到影响。为了弥补这一限制，我们将通过实验和数值方法，研究两种提高使用石墨烯薄膜的光纤声压传感器灵敏度的方法。首先，使用石墨烯 - 银复合隔膜通过提高反射率来增强光学灵敏度。与纯石墨烯隔膜的传感器相比，石墨烯 - 银复合材料可将灵敏度提高三倍，而机械灵敏度基本保持不变。其次，开发一种光纤传感器，通过光纤与石英毛细管之间的间隙扩大背衬空气体积。实验结果表明，与间隙侧空间填充的情况相比，机械灵敏度提高了10倍。对于这两种方法，由于灵敏度提高，信噪比（SNR）得到改善，并且COMSOL热粘性声学模拟与实验结果吻合良好。这项研究不仅有望增进对传感器设计中流固相互作用的理解，还将惠及各种需要高性能微型声学传感器的应用。
