Food and water safety, environmental monitoring and clinical screening are examples of fields where microfluidics can make a significant contribution, since in these areas it is critical to obtain rapid results. Working with microfluidic devices offers important advantages: small sample requirements, higher resolution and sensitivity, and shorter processing times (~minutes).
Intellectual Merit Dielectrophoresis (DEP), an electrokinetic (EK) transport mechanism, is one of the most popular techniques used in microdevices for analyzing cells. Insulator-based DEP (iDEP) offers a dielectrophoretic mode that employs 3-dimensional insulating structures located between two external electrodes. These systems have been extensively studied employing DC potentials and high frequency AC potentials. There is, however, a significant gap in knowledge for particle behavior in iDEP systems with low frequency (< 1 kHz) AC electric potentials. The present proposal is focused on the use of low frequency AC potentials in iDEP systems.
In order to immobilize and concentrate particles in iDEP systems, DEP has to overcome electroosmotic flow (EOF). EOF is necessary as means to pump the liquid and cells through a microchannel, but it is costly for DEP to overcome EOF, since very high potentials are required, which compromises cell viability and produces heat. This proposal aims to dynamically control EOF by modifying the characteristics of an applied AC potential. This is more advantageous than eliminating EOF, since it allows controlling EOF "on the fly," leading to lower voltage requirements. There is great flexibility and novelty on the use of AC electric potentials with iDEP systems, since a new set of parameters can be used to fine tune particle and cell manipulation. By using these parameters (signal shape, frequency, amplitude, offset), EOF can be dynamically controlled to produce more effective cell manipulation at lower required potentials. This work will also employ mathematical modeling that will aid on the understanding of the fundamentals behind iDEP. Integrated systems with the application of sequences of AC and DC potentials and multipart devices comprising sections for streaming DEP and trapping DEP will also be evaluated, with the objective of achieving sorting, concentration and separation of a sample containing various cell types on a single device.
Broader Impacts Scientific impact: The potential of iDEP has not been fully explored; there is a need for systems able to perform several processes on a single device, and low frequency AC potentials can answer this need. This project will advance the state of the art in the applications of iDEP, addressing the gap in the low frequency regime (<1kHz). It will also advance on the knowledge of mathematical modeling of iDEP systems and fundamentals on post geometry. Schemes for cell sorting, separation and concentration will be designed, by integrating several steps of a process on a single device. The possible applications of a microscale method that can process a sample containing several types of cells in a matter of minutes are numerous. This research can make an impact in many other fields, where a rapid response of samples containing cells is critical.
Societal impact: This project will provide a premier research opportunity for undergraduate and graduate students. It will also assist in providing research opportunities for female students through the Women in Engineering program, and for minorities and underrepresented groups, including those students in the RIT Ronald E. McNair Post-Baccalaureate Achievement Program, a program dedicated to low income, first generation minority students to ensure they enter graduate education.
