Collaborative Research: Direct, Nozzle-Free Printing of Functional Nanomaterials Using Ultrasound Bubble Cavitation

该项目旨在提供对无喷嘴液体喷射系统工作机制背后的基础科学的深入了解。广泛使用的最先进的打印技术主要依赖于使用喷嘴来沉积材料。喷嘴可能会堵塞，这会对打印的可靠性和再现性产生不利影响。当高分辨率打印的喷嘴直径减小时，这个问题变得更加严重，这是越来越需要的。此外，印刷含有颗粒、薄片和高纵横比纳米材料的油墨或浆料也很困难。该奖项支持为开发无喷嘴添加剂制造工艺提供知识的研究，该工艺可以消除堵塞并实现高分辨率打印所需的更窄的喷流。超声气泡空化过程可以在刚性和柔性衬底上沉积不同类型、形状和大小的纳米材料。没有喷嘴，消除了堵塞问题。基于纳米材料的可添加制造的设备得到了广泛的应用，从电子到生物材料再到传感器。因此，这项研究的成果对印刷业和国民经济都是有益的。该项目涉及多个学科，包括应用物理、电气工程、机械工程、生物工程和材料科学。多学科研究创造了一个独特的环境，这有助于扩大妇女和代表不足的群体在研究中的参与，并对工程教育产生积极影响。该项目利用YouTube和其他社交媒体平台向更广泛的社区传播知识。该项目研究一种液体喷射系统，该系统由激光产生的聚焦超声波产生的单个空泡来打印各种纳米结构。超声气泡空化印刷过程是无喷嘴的，因此避免了现有喷嘴添加剂制造技术中的堵塞问题。然而，需要对所涉及的液体喷射和能量转换过程背后的基本机制有充分的了解，以实现将该技术用于添加剂制造的全部应用潜力。为了了解超声液体喷射的机理，研究小组开发了气液界面和空化区的声干扰模型、激光闪光阴影图以捕捉气泡形成和喷射的流体动力学，以及气泡形成动力学作为不同物理参数的函数。为了设计高效的光声换能器，该团队研究了激光参数对导致高压幅度的光吸收纳米复合材料中热传输特性的影响，调查了导致高聚焦增益的光声透镜的设计方面，并制造了复合透镜并确定了几何增益、峰值压力幅度和透镜击穿系数。最后，该团队打印纳米材料薄膜，并将打印薄膜的质量和特征与传统打印系统获得的薄膜质量和特性进行比较。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The project aims to provide a robust understanding of the fundamental science behind the working mechanism of a nozzle-free liquid-jetting system. Widely employed state-of-the-art printing techniques rely primarily on the use of nozzles to deposit materials. Nozzles can get clogged, which adversely affects printing reliability and reproducibility. This problem becomes more significant when the nozzle diameter is reduced for high-resolution printing, which is in increasing demand. Additionally, it is difficult to print inks or pastes that contain particles, flakes, and high-aspect ratio nanomaterials. This award supports research to provide knowledge for the development of a nozzle-free additive manufacturing process, which can eliminate clogs and enable narrower jet streams required for high resolution printing. The ultrasound bubble cavitation process enables deposition of different types, shapes, and sizes of nanomaterials on rigid and flexible substrates. The absence of nozzles eliminates clogging problems. Nanomaterial-based additively manufactured devices find a wide range of applications, from electronics to biomaterials to sensors. Therefore, the results from this study benefits the printing industry and the national economy. This project involves several disciplines including applied physics, electrical engineering, mechanical engineering, bioengineering, and materials science. The multi-disciplinary research creates a unique environment, which helps broaden participation of women and underrepresented groups in research and positively impacts engineering education. The project uses YouTube and other social media platforms to disseminate knowledge to a wider community.The project studies a liquid jetting system enabled by a single cavitation bubble created by laser-generated focused ultrasound to print various nanostructures. The ultrasound bubble cavitation printing process is nozzle-less, thus avoiding the clogging problems in existing nozzle-based additive manufacturing techniques. However, a robust understanding of the fundamental mechanism behind the liquid jetting and energy conversion processes involved is needed to realize the full application potential of using this technique for additive manufacturing. To understand the ultrasonic liquid jetting mechanism, the research team develops models of acoustic interference at the air-liquid interface and cavitation zone, laser-flash shadowgraphy to capture the hydrodynamics of bubble formation and jetting, and bubble formation dynamics as a function of varying physical parameters. To design efficient an optoacoustic transducer, the team studies the effect of laser parameters on thermal transport properties in light-absorbing nanocomposite materials leading to high pressure amplitudes, investigates design aspects of photoacoustic lens leading to high focal gain, and fabricates composite lenses and determines the geometric gain, peak pressure amplitude, and lens breakdown factors. Finally, the team prints nanomaterial films, and compares the quality and characteristics of printed films against those obtained with traditional printing systems.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.