Greg McGraw, Rafael Davalos, John Brazzle, John Hachman, Marion Hunter, Jeffery Chames, Gregory Fiechtner, Eric Cummings, Yolanda Fintschenko, Blake Simmons
We have successfully demonstrated selective trapping, concentration, and release of various biological organisms and inert beads by insulator-based dielectrophoresis within a polymeric microfluidic device. The microfluidic channels and internal features, in this case arrays of insulating posts, were initially created through standard wet-etch techniques in glass. This glass chip was then transformed into a nickel stamp through the process of electroplating. The resultant nickel stamp was then used as the replication tool to produce the polymeric devices through injection molding. The polymeric devices were made of Zeonor 1060R, a polyolefin copolymer resin selected for its superior chemical resistance and optical properties. These devices were then optically aligned with another polymeric substrate that had been machined to form fluidic vias. These two polymeric substrates were then bonded together through thermal diffusion bonding. The sealed devices were utilized to selectively separate and concentrate a variety of biological pathogen simulants and organisms. These organisms include bacteria and spores that were selectively concentrated and released by simply applying D.C. voltages across the plastic replicates via platinum electrodes in inlet and outlet reservoirs. The dielectrophoretic response of the organisms is observed to be a function of the applied electric field and post size, geometry and spacing. Cells were selectively trapped against a background of labeled polystyrene beads and spores to demonstrate that samples of interest can be separated from a diverse background. We have implemented a methodology to determine the concentration factors obtained in these devices.
We have applied CZE and CEC in microfluidic devices to a number of analytical problems including the analysis of chemical warfare agents, polycyclic aromatic hydrocarbons, and proteins. In addition to developments in the areas of separations, we are also heavily involved in the "front-end" of analytical systems particularly in the area of sample preconcentration. We have a particular interest in the concentration of a wide range of molecules including small molecules, biopolymers, and cells. Our current toolbox includes a microfluidic platform known as Liquid Phase μChemLab developed by a team at Sandia for protein analysis. This platform has been demonstrated with protein biotoxins, CW agent degradation products, protein preconcentration, and is suitable for other targets. Additionally, electrodeless dielectrophoresis technology developed at Sandia is an attractive alternative to filters for cell concentration.
Capillary electrophoresis (CE) lends itself to miniaturization, because it uses electroosmotic flow rather than moving parts for flow generation. Its analytical figures of merit improve as channel dimensions decrease. However, solution flow in the small planar channels used in CE-on-a-chip is very sensitive to reservoir solution height. This adds a pressure driven flow components, which decreases resolution, sensitivity, and separation efficiency of the EOF-driven technique. We have observed that this contribution to parabolic flow from uneven solution heights can be minimized by using a porous polymer monolith (PPM) as a flow restriction plug in the reservoirs of a 75 micrometers wide X 15 micrometers deep microchannel etched in glass. Our results indicate an average PPM pore size of 1 micrometers is sufficient for flow restriction. Pore sizes below this result in charge trapping of even small dye molecules. Images of the flow profile on and off the monolith show the inverse-parabolic effect on the electroosmotic flow profile due to mismatched zeta potentials between the polymer and the fused silica wall surfaces depending on PPM surface charge and plug length.
Conference Committee Involvement (12)
Microfluidics, BioMEMS, and Medical Microsystems XXIII
26 January 2025 | San Francisco, California, United States
Microfluidics, BioMEMS, and Medical Microsystems XXII
28 January 2024 | San Francisco, California, United States
Microfluidics, BioMEMS, and Medical Microsystems XXI
29 January 2023 | San Francisco, California, United States
Microfluidics, BioMEMS, and Medical Microsystems XX
22 January 2022 | San Francisco, California, United States
Microfluidics, BioMEMS, and Medical Microsystems XIX
6 March 2021 | Online Only, California, United States
Microfluidics, BioMEMS, and Medical Microsystems XVIII
1 February 2020 | San Francisco, California, United States
Microfluidics, BioMEMS, and Medical Microsystems XVII
2 February 2019 | San Francisco, California, United States
Microfluidics, BioMEMS, and Medical Microsystems XVI
27 January 2018 | San Francisco, California, United States
Microfluidics, BioMEMS, and Medical Microsystems XV
28 January 2017 | San Francisco, California, United States
Microfluidics, BioMEMS, and Medical Microsystems XIV
13 February 2016 | San Francisco, California, United States
Microfluidics, BioMEMS, and Medical Microsystems XIII
7 February 2015 | San Francisco, California, United States
Microfluidics, BioMEMS, and Medical Microsystems XII
2 February 2014 | San Francisco, California, United States
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