Sheathless Size-Based Acoustic Particle Separation

Particle separation is of great interest in many biological and biomedical applications. Flow-based methods have been used to sort particles and cells. However, the main challenge with flow based particle separation systems is the need for a sheath flow for successful operation. Existence of the sheath liquid dilutes the analyte, necessitates precise flow control between sample and sheath flow, requires a complicated design to create sheath flow and separation efficiency depends on the sheath liquid composition. In this paper, we present a microfluidic platform for sheathless particle separation using standing surface acoustic waves. In this platform, particles are first lined up at the center of the channel without introducing any external sheath flow. The particles are then entered into the second stage where particles are driven towards the off-center pressure nodes for size based separation. The larger particles are exposed to more lateral displacement in the channel due to the acoustic force differences. Consequently, different-size particles are separated into multiple collection outlets. The prominent feature of the present microfluidic platform is that the device does not require the use of the sheath flow for positioning and aligning of particles. Instead, the sheathless flow focusing and separation are integrated within a single microfluidic device and accomplished simultaneously. In this paper, we demonstrated two different particle size-resolution separations; (1) 3 µm and 10 µm and (2) 3 µm and 5 µm. Also, the effects of the input power, the flow rate, and particle concentration on the separation efficiency were investigated. These technologies have potential to impact broadly various areas including the essential microfluidic components for lab-on-a-chip system and integrated biological and biomedical applications.Bankhead-Coley Florida Cancer Research Program (Grant # 1BN04-34183)National Science Foundation (U.S.) (Grant 0968736)National Science Foundation (U.S.) (Grant 1135419)National Science Foundation (U.S.) (Grant 1056475

Dual-electrode capacitive micromachined ultrasonic transducers for medical ultrasound applications

Capacitive Micromachined Ultrasonic Transducers (CMUTs) have been introduced as a viable alternative to piezoelectric transducers in medical ultrasound imaging in the last decade. CMUTs are especially suitable for applications requiring small size such as catheter based cardiovascular applications. Despite these advantages and their broad bandwidth, earlier studies indicated that the overall sensitivity of CMUTs need to be improved to match piezoelectric transducers. This dissertation addresses this issue by introducing the dual-electrode CMUT concept. Dual electrode configuration takes advantage of leveraged bending in electrostatic actuators to increase both the pressure output and receive sensitivity of the CMUTs. Static and dynamic finite element based models are developed to model the behavior of dual-electrode CMUTs. The devices are then successfully fabricated and characterized. Experiments illustrate that the pulse echo performance is increased by more than 15dB with dual-electrode CMUTs as compared to single electrode conventional CMUT. Further device optimization is explored via membrane shape adjustment by adding a center mass to the design. Electromechanical coupling coefficient (kc2) is investigated as a figure of merit to evaluate performance improvement with non-uniform/uniform membrane dual-electrode CMUTs. When the center mass is added to the design, the optimized non-uniform membrane increases the electromechanical coupling coefficient from 0.24 to 0.85 while increasing one-way 3dB fractional bandwidth from 80% to 140% and reducing the DC bias requirement from 160V to 132V. The results of this modeling study are successfully verified by experiments. With this membrane shape adjustment, significant performance improvement (nearly 20dB) is achieved with the dual-electrode CMUT structure that enables the CMUT performance to exceed that of piezoelectric transducers for many applications.Ph.D.Committee Chair: Degertekin, F. Levent; Committee Member: Benkeser, Paul; Committee Member: Berhelot, Yves; Committee Member: Brand, Oliver; Committee Member: Hesketh, Pete

Bulk Glass Reinforced Composite Columns: Physical Testing Results, Analysis, and Discussion

Glass-reinforced composite columns (GRCCs) may provide an economical alternative to conventional construction materials due to the superior cost to strength provided by bulk glass. Prior to this study, no GRCCs had been physically tested, having previously relied on simulation to predict the behavior of the columns. This study utilizes polyurethane resin bonds in place of sizing agents for adherence between materials, a key requirement for the development of the structural system of the columns. The unreinforced control column failed at a load of 11.2 kN while the maximum GRCC load was 30.8 kN. This indicates that glass can be loaded to 123 MPa before the onset of delamination failure of the GRCCs. Maximum shear stress of 53 MPa was reached, exceeding the 11 MPa required for practical GRCCs. Buckling of the columns occurred at 30.8 kN, below the theoretical maximum of 64.4 kN. Through gradual delamination, the column slowly transferred to an unbonded condition, causing buckling failure. Delamination is unlikely to occur in practical GRCCs due to the lower required shear strengths

Quantification of Bolt Tension by Surface Acoustic Waves: An Experimentally Verified Simulation Study

Quantifying bolt tension and ensuring that bolts are appropriately tightened for large-scale civil infrastructures are crucial. This study investigated the feasibility of employing the surface acoustic wave (SAW) for quantifying the bolt tension via finite element modeling. The central hypothesis is that the real area of contact in a bolted joint increases as the tension or preload is increased, causing an acoustical signature change. The experimentally verified 3-D simulations were carried out in two steps: A preload was first applied to the bolt body to simulate the realistic behavior of bolted joint; and the SAW propagation was then excited on the top surface of the plate to reflect from the bolted joint. The bolt tension value was varied between 4 and 24 kN (properly tightened bolt) in the steps of 4 kN to study the effect of the bolt tension. The results indicate an increased reflected wave amplitude and a gradual phase shift, up to 0.5 µs, as the bolt tension increased. Furthermore, the result shows that the distance between the first reflected wave and the source becomes shorter as the preload increases, as hypothesized. A 1.9 mm difference in the distance between the maximum and minimum preload was observed. As part of this study, the simulation results were also compared with the experimental results, and a good agreement between the simulation and experiments was demonstrated

Arc melted glass piles for structural foundations and method of use

A system for forming a piling structure includes a hollow casing, a control assembly positioned proximately to the hollow casing, and a pivoting support device connected to the control assembly. A pivoting electrode is connected to the pivoting support device and configured to extend into the hollow casing. A second electrode is connected to the control assembly and extends into the hollow casing within the range of motion of the pivoting electrode. An electric power source is connected to the pivoting electrode and the second electrode, wherein charge on the electrodes produces a current arc between the pivoting electrode and the second electrode. A lift mechanism is positioned proximately to the hollow casing to control the electrodes position within the hollow casing

A Noncontact Magneto–Piezo Harvester-Based Vehicle Regenerative Suspension System: An Experimental Study

Recent research has examined the possibility of recovering energy from mechanical vibration induced by a vehicle shock absorber using piezoelectric and electromagnetic transducers. In terms of automotive applications, piezoelectric vibration energy harvesting shows promise for recapturing some (even if small) amounts of vehicle vibration energy, which would otherwise be wasted through the vehicle dampers. Functional materials, such as piezoelectric materials, are capable of converting mechanical energy into useful electrical energy and vice versa. In this paper, an innovative rotational piezoelectric vibration-energy-harvesting device is presented that employs a magnetic coupling mechanism and provides robust performance over a range of frequencies. The piezoelectric energy harvester is driven by a unidirectional suspension system. An experimental investigation was carried out to study the performance of the manufactured prototype. We observed no damage to the prototype after operating continuously at a vibration amplitude of 5 mm at a frequency of 2.5 Hz for over 10,000 cycles. In addition, the presented regenerative suspension system is capable of producing high and relatively steady open-circuit voltages, irrespective of excitation frequencies. The results demonstrate that regenerative shock absorber is robust and has a broad frequency range

Arc melted glass piles for structural foundations and method of use

A system for forming a piling structure includes a hollow casing, a control assembly positioned proximately to the hollow casing, and a pivoting support device connected to the control assembly. A pivoting electrode is connected to the pivoting support device and configured to extend into the hollow casing. A second electrode is connected to the control assembly and extends into the hollow casing within the range of motion of the pivoting electrode. An electric power source is connected to the pivoting electrode and the second electrode, wherein charge on the electrodes produces a current arc between the pivoting electrode and the second electrode. A lift mechanism is positioned proximately to the hollow casing to control the electrodes position within the hollow casing

Dynamically reconfigurable bandpass filters

In one embodiment, a dynamically reconfigurable bandpass filter includes a resonator loop and a microfluidic channel proximate to the resonator loop, the channel containing a conductor, wherein the position of the conductor within the channel can be adjusted to change capacitive loading of the resonator loop and therefore change the frequencies that the filter passes. In another embodiment, a filter includes a second resonator loop having comprising switches located at discrete positions along a length of the second resonator loop, wherein opening and closing of the switches changes the effective length of the second resonator loop to change capacitive loading of the first resonator loop

Active ultrasonic method of quantifying bolt tightening and loosening

A synthetic phased array surface acoustic wave sensor to quantify bolt tension and a method for determining or estimating the tension in bolts using surface acoustic waves (SAWs). The tension is determined or estimated by using the reflection of SAWs created by the bolt head interference with the underlying surface. Increments in the bolt tension raise the points of interaction between the waves and the bolt head (real area of contact), and hence the position of the reflective boundaries. The variations are estimated using known techniques (e.g., linear synthetic array imaging technique). A singular transducer is actuated from predefined positions to produce an array of signals that are subsequently arranged and added to construct an acoustic image

Active ultrasonic method of quantifying bolt tightening and loosening

A synthetic phased array surface acoustic wave sensor to quantify bolt tension and a method for determining or estimating the tension in bolts using surface acoustic waves (SAWs). The tension is determined or estimated by using the reflection of SAWs created by the bolt head interference with the underlying surface. Increments in the bolt tension raise the points of interaction between the waves and the bolt head (real area of contact), and hence the position of the reflective boundaries. The variations are estimated using known techniques (e.g., linear synthetic array imaging technique). A singular transducer is actuated from predefined positions to produce an array of signals that are subsequently arranged and added to construct an acoustic image