Control of Micro/Nano Bio-mimetic Structures for Fluidic Devices

这项工作将研究用于生物流体装置的微/纳米仿生纤毛的最优(最小能量)控制。其目标是实现少量流体的生物兼容传输，而不需要笨重的执行器，例如用于当前设备中的流体传输的外部泵，从而实现设备的便携性。这项拟议工作的新颖之处在于，它将通过模拟生物系统来实现这种生物相容的流体传输；特别是，拟议的设计将使用微/纳米尺度的生物模拟纤毛(类似于生物系统中使用的毛发结构)来进行流体传输。关键的想法是以接近纤毛振动共振的频率不对称地激发仿生纤毛阵列。振动的不对称性产生净流体流动；而激发频率与纤毛阵列的共振频率的接近使得仿生纤毛能够相对较大地运动。主要的控制问题是以最小的输入能量最大化流体流量，以实现设备的便携性。纤毛阵列产生的分布式流体-结构相互作用的优化将使用基于包络的流动预测和子层方法，以及用于以下目的的非线性结构振动建模：(A)对非线性纤毛动力学进行建模；(B)量化纤毛阵列产生的流量；以及(C)优化控制输入以最大化所产生的流量。为了获得最优的控制输入，所提出的工作将解决轨迹跟踪和输出转换的同时优化问题，以最大化纤毛产生的流量，同时最小化输入能量。这项研究还将研究为解决这个非线性优化问题而提出的迭代算法的收敛情况。从这个意义上讲，本文的研究将推动非线性系统最优控制的发展。除了理论上的努力，控制技术还将在实验中实施和评估；因此，这项研究将为实现这种用于流体设备的仿生纤毛奠定基础。这项研究将使在一次性生物流体芯片等新兴应用中实现少量流体样本的生物兼容传输。其目标是通过消除对现有生物流体设备中用于流体传输的外部泵等笨重执行器的需求，来增强生物设备的便携性。拟议的设计将使用微米/纳米尺度的仿生纤毛进行流体传输。生物纤毛是毛发状结构，其有节奏的节拍：(A)为细胞和微生物提供运动；(B)在生物管道中移动液体和颗粒。例如，纤毛在人体内被用来扫除：(I)呼吸系统中的粘液，(Ii)卵子进入子宫。该装置将利用振动/声学来间接激发仿生纤毛，这将导致生物相容的驱动机制，因为它避免了在流体输送过程中对生物样品的破坏。此外，压电致动器(产生振动/声学)和纤毛之间相对容易的耦合将使一次性生物流体芯片能够通过远程致动进行方便的流体传输。这一提议的结果将是一种仿生装置，它将使以下应用能够实现：(A)控制化学反应的扩散速度，(B)有效地混合几种不同的生物/化学物种，或(C)以可控的方式输送液体。拟议的工作将为本科生提供研究和教育经验，并促进少数民族学生参与研究。因此，这将有助于建立新兴生物技术领域所需的研究和人力资源基础设施；这一努力与最近NSF赞助的研讨会一致，该研讨会发现，机械工程系“应该积极将生物和生命科学纳入课程”。

The proposed work will study the optimal (minimal-energy) control of micro/nano bio-mimetic cilia for bio-fluidic devices. The goal is to achieve bio-compatible transport of small amounts of fluids without the need for cumbersome actuators such as external pumps used for fluid transport in current devices thereby, enable device portability. The novelty of the proposed work is that it will achieve this bio-compatible fluid transport by mimicking biological systems; in particular, the proposed design will use micro/nano-scale bio-mimetic cilia (similar to hair-like structures used in biological systems) for fluid transport. The key idea is to asymmetrically excite the bio-mimetic cilia array at frequencies close to vibrational resonance of the cilia. The asymmetry of the vibrations produces net fluid flow; and the closeness of the excitation frequency to the resonance frequency of the cilia array enables relatively large movements of the bio-mimetic cilia. The main control issue is to maximize the fluid flow with minimal input energy for device portability. The optimization of the distributed fluid-structure interactions arising from cilia array will use envelope-based flow prediction and sub-layer methods, along with nonlinear structural vibration modeling for: (a) modeling the nonlinear cilia dynamics; (b) quantifying the flow produced by the cilia array; and (c) optimizing the control input to maximize the resulting flow. To obtain the optimal control input, the proposed work will solve the simultaneous optimization of trajectory tracking and output transitions for maximizing the flow generated by the cilia while minimizing the input energy. The research will also investigate convergence of iterative algorithms proposed to solve this nonlinear optimization problem. In this sense, the proposed research will advance the state-of-the-art in optimal control of nonlinear systems. In addition to the theoretical effort, the control techniques will be implemented and evaluated experimentally; thus, the research will lay the groundwork for enabling such bio-mimetic cilia for fluidic devices.This research will enable the bio-compatible transport of small amounts of fluid samples in emerging applications such as disposable biofluidic chips. The goal is to enhance the portability of bio-devices by removing the need for cumbersome actuators such as external pumps used for fluid transport in current bio-fluidic devices. The proposed design will use micro/nano-scale bio-mimetic cilia for fluid transport. Biological cilia are hair-like structures whose rhythmic beating: (a) provides motility for cells and micro-organisms; and (b) moves fluids and particles in biological ducts. For example, cilia are used in the human body to sweep: (i) mucous in the respiratory system, and (ii) eggs toward the uterus. The proposed device will use vibration/acoustic to indirectly excite the bio-mimetic cilia, which will lead to a biocompatible actuation mechanism since it avoids damage of biosamples during fluid transport. Moreover, the relatively easy coupling between a piezo-actuator (to generate the vibration/acoustics) and the cilia will enable convenient fluid transport through remote actuation for disposable biofluidic chips. The outcome of this proposal will be a biomimetic device that will enable applications which need to: (a) control the diffusion rate of chemical reactions, (b) efficiently mix several different bio/chemical species, or (c) transport liquid in a controllable way. The proposed work will offer research and educational experience to undergraduate students and promote the involvement of minority students in research. Thus, it will help to build the research and human resource infrastructure needed in emerging biotechnology areas; this effort is in keeping with a recent NSF sponsored workshop finding that Mechanical Engineering Departments "should aggressively integrate biology and life sciences into the curriculum."