One of the principal challenges of primary blast injury research is imitation of shock waves accurately and consistently in a safe and tunable platform. Existing simulators have been effective in these goals but have not been conducive for in vitro models due to their large size and air-mediated wave propagation.
In this thesis, a redesigned benchtop shock wave generator (SWG) has provided a platform for in vitro models. A pulsed power generator charges a capacitor and discharges the capacitor through a bridge wire. The discharge causes the bridge wire to experience phase changes, momentarily becoming a gas or plasma. In this moment, the bridge wire expands radially and creates a pressure wave in the surrounding water. As the wave propagates, it forms a shock wave and strikes the cell platform at the far end of the conical tank. Current design efforts are focused on the tunability of the SWG, by varying the bridge wire material and diameter.
Five materials at three bridge wire diameters have been tested. Each bridge wire was inserted into the SWG via a pinching mechanism. Either side of the pinching mechanism was connected to either terminal of the capacitor. When the pulsed power generator was cycled, the bridge wire was vaporized and generated a shock wave. A piezoelectric sensor near the wide end of the tank recorded the passing of the shock wave, which was used to derive various pressure metrics that correlate to injury. The sample size for each combination of diameter and material was five, with a grand total of seventy-five samples run.
Two-way ANOVAs measuring the impacts of bridge wire material and diameter on a variety of shock wave metrics found that the diameter played a significant role in determining the peak overpressure and positive impulse generated while the main effect of material played a much smaller role. The interaction between material and diameter was also found to be significant.
The tunable benchtop SWG provides a platform for exploration of primary blast injury using in vitro models. By adjusting the bridge wire diameter, the SWG can generate waves with a variety of shock wave metrics, providing an opportunity for researchers to address various degrees of injury. With the addition of this technology to the efforts to understand primary blast injury, development of treatments and protective equipment can be expedited. / Master of Science / Primary blast injury, the injury caused by the blast wave moving through the body, has been affecting those exposed to blast for nearly a century, since the regular use of conventional explosives in World War I. As equipment and war has changed in the past two decades, there has been heightened interest in understanding the effects of blast waves on the body. To assist in this research, blast wave simulators have been developed to recreate the blast wave in a controlled environment. However, current designs are not conducive to experiments on cultured cells.
A new blast wave simulator, called the shock wave generator (SWG), has been designed as a platform for cultured cell-based experiments. The simulator generates a shock wave by exploding a thin bridge wire using high electrical current. The explosion occurs underwater, generating a shock wave capable of injuring cells at the opposite end of the tank.
A platform such as this provides multiple opportunities to tune the pressure metrics related to the shock waves. Bridge wire material and volume play critical roles in the resulting shock wave, working together to define the amount of energy required to vaporize the bridge wire. Five materials and three diameters, a derivative of the wire volume, were investigated to determine their impacts on the resulting peak pressure, positive duration, and positive impulse.
While wire material was not found to have a significant impact on peak pressure, wire diameter had a significant effect on the resulting overpressures. The thickest wire generated the lowest peak pressure while the thinner wires generated higher peak pressures. The thinner wires were not significantly different from one another. A similar result was found for positive duration and impulse.
Overall, the use of an exploding wire to generate shock waves is applicable as an injury mechanism for cell cultures in primary blast injury research. This work along with future work will provide a tunable and controlled platform that has opened a new frontier for investigating the primary blast injury.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/115713 |
| Date | 10 July 2023 |
| Creators | Showalter, Noah Wade |
| Contributors | Department of Biomedical Engineering and Mechanics, VandeVord, Pamela J., Srinivasan, Bhuvana, Jacques, Eric Jean-Yves |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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