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

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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."