EAGER: Monolithic Phononic Crystals and Programmable Surface Acoustic Wave Microfluidics

在过去的几十年里，许多重大的技术突破主要是由于我们能够控制两种基本粒子：电子和光子。声子是另一种重要的基本粒子，负责热量和声音的传递。然而，只有有限的研究集中在利用声子来满足我们的需要。收集声子，特别是表面声波，可以产生具有新特性的新型实用微流体装置。声子可以对生物粒子（病毒、细菌和细胞）施加强大的辐射力，并能高精度、高效率地操纵它们。这个建议提供了使用声子晶体来实现这一点。这种声子晶体与微流体的结合为微流体系统中表面声波的控制提供了前所未有的水平。这种能力可能会导致单片，超紧凑，通用和可编程的微流体装置。声子学和微流体学的融合可以打开一扇通往芯片生物医学技术实验室新世界的大门，并以以前无法想象的方式影响日常生活，就像电子和光子迄今为止所做的那样。该计划的教育部分预计将为UCSC的本科生和研究生提供物理，电气工程和生物科学方面的跨学科培训。研究成果将整合到研究生课程中，并通过“工程项目中的女生”向中学女生和“多元文化工程项目”向代表性不足的少数族裔进行报告，将研究结果传播给更广泛的受众。本研究计划的目标是探索利用硅衬底上的声子晶体开发具有新功能的微流体装置的可行性。声子晶体提供了无限的剪裁声波的方法。然而，到目前为止，它们还没有用于声微流控应用，除了一些简单的应用，涉及在露天固体衬底上的微滴的混合和引导。连续流微流体和声子晶体的完全集成还有待证明。本项目旨在通过利用带隙形成和缺陷态的消失模式等概念，展示声子晶体在声流体中的实际、简便的应用。在这个为期一年的计划中，将探讨两个基本的设计概念：(i)声子晶体反射器，以及（ii）声子晶体波导结构。这两种结构提供了一套完整的基本构建模块，以实现更复杂的声子晶体微流体，具有增强的功能（见下面的动机部分）。这个为期一年的项目有四个具体目标：(1)通过理论建模和有限元模拟设计声子晶体器件。(2)制造声子晶体器件，并在硅衬底上与数字间换能器集成。(3)对集成结构的表面声波特性进行表征。(4)将微流体与声子晶体和数字间换能器相结合，实现基于尺寸的微颗粒分离和微颗粒导向。提出的研究计划涉及单片声流系统的数值设计，其中声子晶体通过诸如有限元方法等技术来处理粒子操纵。这些器件采用成熟的微加工技术制造，如光刻、金属沉积、软光刻和深度反应离子蚀刻。在本提案中，微流体测试将仅限于荧光二氧化硅颗粒，用于快速设备开发目的。

The last few decades, a number of major technological breakthroughs are mainly enabled by our ability to control two elementary particles: electrons and photons. Phonon is another important elementary particle that is responsible from heat and sound transfer. However, there are only limited studies focused on exploiting phonons for our needs. Harvesting phonons, specifically surface acoustic waves, could lead to new practical microfluidic devices with novel properties. Acoustic phonons can exert strong radiation forces to bioparticles (viruses, bacteria and cell) and manipulate them with high precision and efficiency. This proposal offers using phononic crystals to achieve this. Incorporation of such phononic crystals with microfluidics provides an unprecedented level of control on surface acoustic waves in microfluidic system. This capability can potentially lead to monolithic, ultra-compact, versatile and programmable microfluidic devices. Fusing of phononics and microfluidics could open door to a new world of lab-on-chip biomedical technologies and impact everyday life in previously unthinkable ways, in a similar fashion to how electrons and photons did so far. The educational component of this program is expected to provide UCSC undergraduate and graduate students with interdisciplinary training in physics, electrical engineering and biological sciences. Outcomes of the research will be integrated in a graduate student curriculum and results will be disseminated to broader audience by presentations to middle school Girls through 'Girls in Engineering Program' and to underrepresented minorities through 'Multicultural Engineering Program' The objective of this research proposal is to explore the feasibility of developing microfluidic devices with new functionalities using phononic crystals on silicon substrates. Phononic crystals offer potentially unlimited ways of tailoring acoustic waves. However, to date, they have not been used in acousto-microfluidic applications, other than few simple applications related to mixing and guiding of microdroplets resting on a solid substrate in open air. Full integration of continuous flow microfluidics and phononic crystals has yet to be demonstrated. This project aims to demonstrate practical, facile utilization of phononic crystals in acoustofluidics by making use of the concepts such as band gap formation and evanescent modes of defect states. In this one-year proposal, two basic design concepts will be explored: (i) phononic crystal reflectors, and (ii) phononic crystal waveguide structures. These two structures offer a complete set of basic building blocks to achieve more complex phononic crystal microfluidics with enhanced capabilities (see motivation section below). This one-year project has four specific goals: (1)To design phononic crystal devices with theoretical modeling and finite element simulations. (2)To fabricate of phononic crystal devices and integrate them with interdigital transducers on a silicon substrate. (3)To characterize surface acoustic wave behavior of the integrated structures. (4)To integrate microfluidics with phononic crystals and interdigital transducers to achieve size based micro-particle separation and micro-particle guiding. The proposed research program involves numerical design of monolithic acoustofluidic systems in which particle manipulation is taken care of by phononic crystals through techniques, such as finite-element method. The devices are fabricated using well-established microfabrication techniques such as photolithography, metal deposition, soft lithography and deep reactive ion etching. In this proposal, microfuidic testing will be limited to fluorescent silica particles for rapid device development purposes.