Interaction of acoustic waves and microbubbles occurs in numerous biomedical applications including ultrasound imaging, drug delivery, lithotripsy treatment, and cell manipulation, wherein the acoustically driven microbubbles routinely act as active microscale oscillators or actuators. In contrast, microbubbles were utilized here as passive receivers to detect broadband ultrasound waves in aqueous environments. The microbubble was photothermally generated on a microstructured optical fiber (MOF) tip, forming a flexible Fabry–Perot cavity whose gas–water interface was sensitive to ultrasound waves. The MOF severed as both a low-loss waveguide and a compact light condenser, allowing high-efficiency generation and stabilization of ultrasmall microbubbles. Integrated with all-fiber interferometry, a 10 μm diameter microbubble exhibited a low noise-equivalent pressure level of ∼3.4 mPa/Hz1/2 and a broad bandwidth of ∼0.8 MHz, capable of detecting weak ultrasounds emitted from red blood cells irradiated by pulsed laser light. With advantages of high sensitivity, compact size, and low cost, the microbubble-based ultrasound sensor has great potential in biomedical imaging and sensing applications.

中文翻译：

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基于柔性微泡的法布里-珀罗腔用于灵敏的超声检测和宽视野光声成像

声波和微泡的相互作用发生在许多生物医学应用中，包括超声成像、药物输送、碎石治疗和细胞操作，其中声学驱动的微泡通常充当有源微尺度振荡器或致动器。相比之下，这里利用微泡作为被动接收器来检测水性环境中的宽带超声波。微气泡是在微结构光纤 (MOF) 尖端上光热产生的，形成一个灵活的法布里-珀罗腔，其气-水界面对超声波敏感。MOF 既是低损耗波导又是紧凑型聚光器，可以高效产生和稳定超小微气泡。与全光纤干涉测量相结合，直径为 10 μm 的微泡具有约 3.4 mPa/Hz1/2 的低噪声等效压力水平和约 0.8 MHz 的宽带宽，能够检测由脉冲激光照射的红细胞发出的微弱超声波。基于微泡的超声传感器具有灵敏度高、体积小、成本低等优点，在生物医学成像和传感应用中具有巨大的潜力。