293303 Temperature Measurement in a Microfluidic Platform for Insulator-Based Dielectrophoretic Protein Manipulations

Tuesday, October 30, 2012
Hall B (Convention Center )
Asuka Nakano, Kathleen Bush and Alexandra Ros, Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ

Direct current (DC) insulator-based dielectrophoresis (iDEP) has been used with cells and biomolecules such as DNA and protein for separation, pre-concentration, and fractionation. Unlike other existing analytical techniques, DEP response is governed by a particle's polarizability in an inhomogeneous electric field. This additional parameter space facilitates improved separation in a gel-free environment which is of particular importance for more complex samples such as disease markers found in bodily fluids. DC iDEP has potential to be used as an alternative to AC iDEP since DC iDEP does not require electrokinetic and/or pressure pumps necessary in AC iDEP experiments. Despite this advantage, the application of large DC voltage in iDEP results in heat generation known as Joule heating within the microfluidic device. This phenomenon is of great interest due to its influence on protein migration and stability and has not been thoroughly investigated experimentally under iDEP conditions. In this work, we present a means to measure fluid temperature in microfluidic systems by implementing fluorescence microscopy with dual color detection via a beam splitter and CCD camera. We have demonstrated a way to quantify the fluorescence emission ratio of a temperature sensitive dye, Rhodamine B (RhB), and a temperature insensitive dye, Rhodamine 110 (Rh110), using the same device developed for our protein DEP experiments. Our preliminary experiments show that there is no significant temperature rise either within the channel or reservoir when low conductivity buffers are used. This experimental finding is in agreement with numerical simulations. 

In addition to DC iDEP, our scope can be further expanded to temperature measurements within a channel with smaller structures and constrictions (i.e. nano-posts). In combination with AC iDEP, nanostructures can provide larger DEP forces to immobilize proteins via DEP trapping making it important to measure temperature fluctuations due to the expected increase in Joule heating effects in small constrictions. Our study provides valuable information about the micro- and nano-environment in which protein iDEP experiments are performed leading to a more profound understanding of protein iDEP.

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