Dielectrophoresis is an analytical technique which involves electroosmotic flow, electrophoresis, and dielectrophoretic force. These factors, when in correct proportions for a given analyte, allow for dielectrophoretic trapping, otherwise known as dielectrophoretic capture. Non-uniform electric fields are required for this phenomenon, and the device in this trial used to induce such an electric field was a gradient insulator-based design. Similar devices have been previously used to separate or identify a wide variety of analytes within solution. Much of the previous work has been focused on the differences in dielectrophoretic trapping between strains of bacteria, whereas this experiment focused on the differentiation of phenotypes within a single bacterial strain, Staphylococcus aureus isolate 35984. A control sample was tested, as well as a sample heated at 70oC for 15 minutes to induce phenotypic changes. The control sample was found to exhibit dielectrophoretic capture at a given gate at a potential of 800V and higher, whereas the heated sample was not observed to capture at any potential in this experiment, which reached a maximum of 1200V. Notably, neither of the samples were found to capture at or below 600V. The results of this experiment were encouraging, though it is worth noting that several experimental trials failed to produce any noteworthy results. As such, the procedure of this experiment should be refined to increase reproducibility of results.

An electric field can be applied to a microfluidic device in order to stop particle flow. Electroosmosis, electrophoresis, and dielectrophoresis act on the particles in different directions in the microfluidic channel, and when these forces create zero net force, the particle stops in the channel. The goal of the performed experiments is to investigate whether hydrostatic pressure generated by a syringe pump could help concentrate these particles and separate them from other contents. Introducing precise, adjustable hydrostatic pressure from the syringe pump provides another mechanism for controlling particle behavior. A microfluidic channel was crafted into a device connected to a syringe pump, and videos of 1 µm silica particles in the device were recorded under a microscope in order to show that samples could be infused into the device and concentrated or captured at a specific location in the channel using hydrostatic pressure. Capture of the particles occurred with and without controlled hydrostatic pressure, but these events occurred somewhat consistently at different voltages. In addition, particle movement in the channel with the syringe pump off was originally attributed to the electrokinetic forces. However, when compared to experiments without the syringe pump connected to the device, it became evident that the electrokinetic forces should have moved the particles in the opposite direction and that, in actuality, there is an inherent pressure in the device also affecting particle movement even when the syringe pump is not turned on.