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

声波在通信和成像中至关重要，包括医疗超声，声纳和地震仪。听诊--倾听身体的声音--是医生评估病人健康状况的第一件事。心脏活动、血液流动和肺部气体交换都有独特的声音，对于受过训练的医生来说，这些声音可以用来快速识别身体功能中的问题。也可以想象，细胞、细菌和病毒都产生不同的声学信号。能够窃听这个声学世界不仅是一个重大的科学突破，而且还将改变我们监测健康、诊断疾病的能力，特别是在早期阶段，并帮助回答基本的生物学问题。然而，在被其他声音的嘈杂声包围的情况下，检测来自小生物物体的微妙声学特征将需要一种新的倾听方法：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，并具有强大的方向性和距离限制感知能力。目前的机电听诊器和水听器没有被设计成推动听诊的极限，也没有按比例缩小到非常接近声源操作。为了解决这些缺点，该提案寻求设计小型纳米级光纤，可以有效地将微弱的声波转换为可以用光电探测器或相机测量的光信号。该设计的工作原理涉及装饰软聚合物涂层的金属纳米颗粒，该涂层响应极低振幅的声波而移动，从而产生对检测到的声学特征唯一的调制光信号。该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，通过促进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民族学生入学人数。通过教授如何使用多样化的跨学科科学来加速科学发现和创新，该项目也将在招募和留住UCSD工程学位课程中代表性不足的少数民族学生方面发挥关键作用。该提案旨在设计，制造，并评估利用强近场等离子体的声光纳米级换能器，介电耦合效应，以检测和解释以前从未听到过的其他本地纳米耳朵的声音签名。将合成阻抗优化的声可压缩聚合物纳米颗粒包覆层，其能够对嵌入或附着在聚合物层中的等离子体纳米颗粒进行强的声学调制。它将被证明，这些包层可以被调谐到调制的弱声波在光学近场具有广泛的频率和振幅。通过激光多普勒测振仪和高速数字全息显微镜，等离子体机械转换机制的声共振和响应将与包层变形研究完全相关，从而深入了解如何利用各种参数（光波长、纳米颗粒尺寸/形状、聚合物成分/厚度等）。以控制微听诊装置的性能和响应。定向响应模式和频率依赖性灵敏度将使用定制的锂酸盐换能器来量化，这将有助于填补关于声学近场如何耦合到远场的知识空白，并且将证明微听诊设备足够灵敏以检测和识别来自纳米生物力学系统的声学特征（例如，该奖项反映了NSF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.