Microauscultation devices via acoustic coupling with near-field light-matter interactions

声波在通信和成像中是至关重要的，包括医学超声、声纳和地震仪。听诊——听身体的声音——是医生评估病人健康状况所做的第一件事。心脏活动、血液流动和肺气体交换都有独特的声音，训练有素的医生的耳朵可以用来快速识别身体功能的问题。同样可以想象的是，细胞、细菌和病毒都能产生不同的声音信号。能够窃听这个声音世界不仅是一项重大的科学突破，而且还将改变我们监测健康、诊断疾病（特别是在早期阶段）的能力，并有助于回答基本的生物学问题。然而，在被其他杂音包围的情况下，从微小的生物物体中检测细微的声学特征将需要一种新的聆听方法：可以接近声源大小的设备，在广泛的声学频率范围内具有卓越的灵敏度，并且具有强大的定向和距离限制的感官能力。目前的机电听诊器和水听器的设计并不能突破听诊的极限，也不能缩小到离声源非常近的地方。为了解决这些缺点，该提案寻求设计小型纳米级光纤，可以有效地将弱声波转换为可以用光电探测器或相机测量的光信号。该设计的工作原理是将金属纳米颗粒装饰在柔软的聚合物涂层上，该涂层会响应极低振幅的声波而移动，从而产生一种调制的光信号，这种光信号是检测到的声学特征所独有的。这个项目将对学生的学习、成就、多样性和包容性产生重大影响。例如，将开发“纳米之夏”研讨会，通过激发加州大学圣地亚哥分校与墨西哥以及当地圣地亚哥高中之间的跨境关系，增加加州大学圣地亚哥分校和其他高等教育机构STEM学位课程中代表性不足的少数族裔学生的入学人数。通过教授如何使用多样化、跨学科的科学来加速科学发现和创新，该项目也将在加州大学圣地亚哥分校工程学位项目中招募和留住代表性不足的少数民族学生方面发挥关键作用。本提案旨在设计、制造和评估声光纳米级换能器，该换能器利用强近场等离子体-介电耦合效应来检测和解释其他局部纳米耳朵从未听到过的声音特征。将合成阻抗优化的声可压缩聚合物纳米纤维包层，使嵌入或附着在聚合物层上的等离子体纳米粒子具有强大的声学调制能力。我们将证明这些包层可以被调谐到在宽频率和振幅范围内的光学近场弱声波调制。通过激光多普勒振动测量和高速数字全息显微镜，等离子体力学转导机制的声学共振和响应将与包层变形研究充分相关，从而深入了解如何利用各种参数（光波长、纳米颗粒大小/形状、聚合物成分/厚度等）来控制纳米纤维微听诊装置的性能和响应。定向响应模式和频率依赖的灵敏度将使用定制的铌酸锂换能器进行量化，这将有助于填补声学近场与远场耦合的知识空白，并且将首次证明纳米纤维微听诊设备足够敏感，可以检测和转导来自纳米生物力学系统的声学特征（例如，病毒衣壳的基因组喷射）。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Sound waves are crucial in communication and imaging, including medical ultrasound, sonar, and seismography. Auscultation—listening to the sounds of the body—is one of the first things a physician does to assess the health of a patient. Heart activity, blood flow, and pulmonary gas exchange all have unique sounds that to a trained physician’s ear can be used to quickly identify problems in bodily functions. It is also conceivable that cells, bacteria, and viruses all generate distinct acoustic signals. Being able to eavesdrop on this acoustic world would not only be a significant scientific breakthrough but would also transform our ability to monitor our health, diagnose disease, particularly at an early stage, and help answer fundamental biological questions. However, detecting the subtle acoustic signatures from small biological objects while surrounded by a cacophony of other sounds will require a new approach to listening: devices that can approach the size of the sound source, have exceptional sensitivity over a broad range of acoustic frequencies, and have a strong directional and distance-limited sensory capability. Current mechanoelectrical stethoscopes and hydrophones are not engineered to push the limits of auscultation nor be scaled down to operate extremely close to acoustic sources. To address these shortcomings, this proposal seeks to engineer small nanoscale fiber optics that can efficiently convert weak sound waves into an optical signal that can be measured with a photodetector or camera. The working principle of the design involves metal nanoparticles decorating a soft polymer coating that moves in response to extremely low amplitude sound waves, creating a modulated optical signal unique to the detected acoustic signature. This project will have a major impact on student learning, achievement, diversity, and inclusion. For example, “Summer of Nano” workshops will be developed to increase underrepresented minority student enrollment numbers in STEM degree programs at UC San Diego, and other higher education institutes, by galvanizing cross-border relationships between UC San Diego and Mexico as well as local San Diego high schools. Through teaching about how diverse, cross-disciplinary science can be used to accelerate scientific discovery and innovation, this project will also be pivotal in recruiting and retaining underrepresented minority students in engineering degree programs at UCSD.This proposal aims to design, fabricate, and evaluate acoustic-to-optical nanoscale transducers that leverage strong near-field plasmon-dielectric coupling effects to detect and interpret sound signatures never heard before by other local nano-ears. Impedance-optimized acousto-compressible polymer nanofiber cladding layers will be synthesized that enable strong, acoustic modulation of plasmonic nanoparticles embedded in, or attached to, the polymer layer. It will be demonstrated that these cladding layers can be tuned to be modulated by weak sound waves in the optical near field with a broad range of frequencies and amplitudes. Through laser Doppler vibrometry and high-speed digital holographic microscopy, the acoustic resonance and response of the plasmomechanical transduction mechanism will be fully correlated to the cladding deformation studies, providing a deep understanding of how to leverage various parameters (light wavelength, nanoparticle size/shape, polymer composition/thickness, etc.) to control the performance and response of the nanofiber microauscultation devices. The directional response pattern and frequency-dependent sensitivity will be quantified using custom lithium niobate transducers, which will help fill the intellectual gap on how the acoustic near field couples to the far field, and it will be demonstrated that the nanofiber microauscultation devices are sensitive enough to detect and transduce acoustic signatures from nanobiomechanical systems (e.g., genome ejection from viral capsids) for the first time.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.