Publications

Davalos, Rafael V.; Krafcik, Karen L.; Salmi, Allen J.; Van De Vreugde, James L.; Mosier, Bruce P.; Morales, Alfredo M.

Microsystems pose unparalleled opportunity in the realm of real-time sample analysis for multiple applications, including Homeland Security monitoring devices, environmental monitoring, and biomedical diagnostics. The need for a universal means of processing, separating, and delivering a sample within these devices is a critical need if these systems are to receive widespread implementation in the industry and government sectors. Efficient particle separation and enrichment techniques are critical for a range of analytical functions including pathogen detection, sample preparation, high-throughput particle sorting, and biomedical diagnostics. Previously, using insulator-based dielectrophoresis (iDEP) in microfluidic glass devices, we demonstrated simultaneous particle separation and concentration. As an alternative to glass, we evaluate the performance of similar iDEP structures produced in polymer-based microdevices and their enhancement through dynamic surface coatings. There are numerous processing and operational advantages that motivate our transition to polymers such as the availability of numerous innate chemical compositions for tailoring performance, mechanical robustness, economy of scale, and ease of thermoforming and mass manufacturing. The polymer chips we have evaluated are fabricated through an injection molding process of the commercially available cyclic olefin copolymer Zeonor{reg_sign}. We demonstrate that the polymer devices achieve the same performance metrics as glass devices. Additionally, we show that the nonionic block copolymer surfactant Pluronic F127 has a strong interaction with the cyclic olefin copolymer at very low concentrations, positively impacting performance by decreasing the magnitude of the applied electric field necessary to achieve particle trapping. The presence of these dynamic surface coatings, therefore, lowers the power required to operate such devices and minimizes Joule heating. The results of this study demonstrate that polymeric microfluidic devices with surfactant coatings for insulator-based dielectrophoresis provide an affordable engineering strategy for selective particle enrichment and sorting.

Davalos, Rafael V.; Fiechtner, Gregory J.; Kanouff, Michael P.; Fintschenko, Yolanda F.; Salmi, Allen J.; Ceremuga, Joseph T.

This report focuses on and presents the capabilities of insulator-based dielectrophoresis (iDEP) microdevices for the concentration and removal of water-borne bacteria, spores and inert particles. The dielectrophoretic behavior exhibited by the different particles of interest (both biological and inert) in each of these systems was observed to be a function of both the applied electric field and the characteristics of the particle, such as size, shape, and conductivity. The results obtained illustrate the potential of glass and polymer-based iDEP devices to act as a concentrator for a front-end device with significant homeland security and industrial applications for the threat analysis of bacteria, spores, and viruses. We observed that the polymeric devices exhibit the same iDEP behavior and efficacy in the field of use as their glass counterparts, but with the added benefit of being easily mass fabricated and developed in a variety of multi-scale formats that will allow for the realization of a truly high-throughput device. These results also demonstrate that the operating characteristics of the device can be tailored through the device fabrication technique utilized and the magnitude of the electric field gradient created within the insulating structures. We have developed systems capable of handling numerous flow rates and sample volume requirements, and have produced a deployable system suitable for use in any laboratory, industrial, or clinical setting.