Abstract

Microfluidic techniques have been shown to address limitations of reconfigurable radio frequency (RF) antennas and filters in efficiency, power handling capability, cost, and frequency tuning. However, the current devices suffer from significant integration challenges associated with packaging, actuation, and control. Recent advances in reconfigurable microfluidics that utilize the motion of a selectively metalized plate (SMP) for RF tuning have demonstrated promising RF capabilities but have exposed a need for an accurate fluid actuation model. This research presents models for the dynamics of plate actuation under multiple scenarios. In the first phase, the mechanical motion of a moving plate (e.g. SMP) in a channel is predicted based on input variables that include microfluidic channel size, fluid properties, driving pressure actuation, etc. Then the analytical model presented here will be solved to calculate the response time, SMP velocities, etc., and compare these results with the desired design values. This model facilitates understanding of the actuation response of an RF tuning system based on a moving plate independent of the actuation method. This model is validated using a millimeter-scale plate driven by a gravitational pressure head as a quasi-static pressure source. Measurements of the prototyped device show excellent agreement with the analytical model; thus, the designer can utilize the presented model for designing and optimizing a microfluidic-based reconfigurable RF device and selecting actuation methods to meet desired outcomes. To examine model accuracy at device scale, recent papers in the microfluidics reconfigurable RF area have been studied, and excellent agreement between our proposed model and the literature data is observed. In the second phase, Electrowetting on dielectric (EWOD) driven micropump is introduced. Beyond actuating the liquid itself, EWOD can also be used to manipulate physical objects via droplets. In this approach, droplets serve as intermediaries to move, position, or assemble microscale components. While this concept has potential applications in microfluidically reconfigured RF devices, it has received significantly less attention compared to direct liquid actuation. The current microfluidic-based RF devices have been primarily based on mechanical micropumps such as diaphragm micropumps, rotary micropumps, and peristaltic micropumps, which all require expensive clean-room fabrication methods and are limited in terms of size. An EWOD pump is proposed as a microfluidic pump that manipulates liquid droplets in a channel, offering an alternative approach to traditional mechanical pumps. This thesis presents an analytical model for an EWOD semi-continuous pump as an alternative actuation method. This model considers the competing electrowetting force, friction force, and fluid inertia force in a one-degree-of-freedom channel, providing valuable insights into the dominant physical processes and enabling better control. The model is validated with an EWOD experiment, demonstrating less than a 6% error between the measured and predicted maximum droplet velocity, and a maximum 7.4% error in the EWOD pump static pressure. The conditions such as dimensions, material, and response time that can improve the performance of an EWOD system to provide a competitive actuation system are identified. In the third phase, another technique is introduced to increase actuation speed of a moving plate (e.g. SMP) using EWOD forces. In the proposed configuration, the plate is supported by four droplets. The top plate is coated with hydrophilic material and the bottom plate is coated with hydrophobic material. The actuation velocity determines the tuning speed of the device. The velocity increases by maximizing the actuation force, minimizing the moving mass (droplets and metallized plate), and reducing all resistances (contact line drag, fluid drag). An analytical model of EWOD actuation that can calculate the relation between the physical dimensions and velocity of the EWOD-actuated system was built and validated experimentally. The main advantage of the proposed system over previous works is the simple 2D manufacturing process, which allows embedding of metalized plates and RF circuit boards, in addition to being compact, portable, and low-cost. In addition, the proposed method does not have any mechanical components, which can increase the system's reliability in a harsh environment.

Degree

PhD

College and Department

Ira A. Fulton College of Engineering; Mechanical Engineering

Rights

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