Electrochemical Characterization Of Polyacrylamide Nanoporous In Nanofluidic Chips

The impetus for concentrating on nanofluidic as a distinct field stemmed from advances in micro-fabrication that enabled the construction of well controlled nanostructures. thus presenting new opportunities to refine our understanding of nano-scale processes and explore their use for chemical analysis. Electrical characteristics of polymer nanoporous structure (nanoporous structure, NPS) were studied in nanofluid chip. Impedance test has been conducted based on electrochemical impedance spectroscopy, and geometric features of the gel structure is analyzed utilizing the experimental data. This article mainly included:The basic theory of electrochemical detection and equivalent detection circuit model of NPS were analyzed. Overlapping phenomenon of electric double layer (EDL) in the diluted solution because of EDL thickness and channel height ratio decreasing in nanofluidic was analyzed. The change of electric characteristic parameters such as electrical conductivity which caused by electric double layer overlap was explained. We estimated the micro channel resistance according to the conductivity formula to preprocess the experimental data.Microfluidic chip integrated with different polyacrylamide NPS was fabricated. The influence of electrolyte concentration on the impedance amplitude and phase was analyzed based on the chip. The results showed that impedance amplitude had a relationship with the KCl concentration in low frequency area. While in the high frequency phase, frequency had little impact on the impedance response, and the increasing concentration made the characteristics frequency of the system increase.Electrode process has been analyzed from the view of reaction kinetics. The impedance data under different KCl concentration have been standardized using maximum average value of impedance, and been plotted vs. normalized frequency. It turned out that there was a peak in standardized imaginary part when the normalized frequency is about 1, data under different concentration overlapped into a single curve. The relationships of electrolyte concentration with the charge transfer resistance and time constant in NPS were researched. Results indicated that under the same concentration, although crosslinking ratio changed the resistance of the gel and gel electric double layer capacitor, there was no difference of relaxation process speed in the system. In order to further discuss the relationship between NPS geometric characteristics and impedance based on the predecessors’comparative study of the aperture and the change trend of the charge transfer resistance, it was found when the NPS aperture was minimum, charge transfer resistance reached to maximum value; conversely, when NPS aperture was maximum, charge transfer resistance became minimum. Charge transfer resistance was applicable to determine the characteristics of the NPS. It revealed that the electrode process of the whole system was dominated by charge transfer which was only controlled by one kind of activation energy.This paper provides research foundation for further exploring the characterization of polyacrylamide NPS using electrochemical method.