Generation of Nonbiased Hydrodynamic Injections on Microfluidic Devices Using Integrated Dielectric Elastomer Actuators

Abstract

Sample introduction is a crucial, yet often overlooked step in chemical analysis. Its importance is clearly portrayed in the case of electrokinetic injection for electrophoretic separations, where sampling bias favors the introduction of the fastest moving analytes in a mixture. To this end, a poly(dimethylsiloxane) (PDMS)-based microfluidic device that incorporates miniaturized and fully integrated dielectric elastomer actuators (IDEAs) in order to perform sample injection for electrophoresis is reported. These electromechanical actuators produce hydrodynamic fluid pulses within the channel network without the need for any modifications to the channel design and without the use of large, off-chip equipment. Separations of Fluorescein thiocarbamyl-labeled amino acids reveal that IDEA-derived injections have a more stable chemical composition than electrokinetic injections, with peak area relative standard deviations (RSDs) less than 1.1% over 30 injections at six different volumes. Moreover, the efficiency and resolution of separations with IDEA-derived injections are not significantly different from electrokinetic injections under similar separation conditions. The reproducibility of peak heights and peak areas over the course of 64 consecutive injections reveal that the actuation mechanism is very stable with peak area RSDs less than 1.8%. These results, coupled with facile fabrication and operation of IDEA devices, suggest that widespread adaptation of this technology could be very advantageous for many types of miniaturized analysis systems.