Communication—Electrochemical Impedance Signature of a Non-Planar, Interdigitated, Flow-Through, Porous, Carbon-Based Microelectrode

Abstract

Top and bottom microelectrode glass slide sandwiches a channel made of adhesive tape and packed with reduced graphene oxide to make a new non-planar interdigitated microfluidic device. Novel device integration allows packing of any transducer material at room temperature with no instrument. Electrical impedance spectroscopy signal is stable over long times, fits an equivalent circuit with well-defined circuit elements. Flow visualization concurs that electric double-layer signal shifts to high frequency due to disruption of the diffusive process from increased convective flow. Charge transfer resistance appears at higher frequencies making the device rapid with high signal to noise ratio.

Electrode_configuration_DNA_Sensitivity_Biomicrofluidics

“…In this work, we show the DNA sensitivity of (NP-µIDE) that packs carbon-based transducer materials between the bottom and top microelectrode. As has been shown earlier and here, our fabrication and device integration process is simple, easy to set up, cost-effective, and requires minimal operator handling/expertise 24 . NP-µIDE with packed carbon materials increases convective transport, disrupting the diffusive dynamics that govern the EDL.…”

“…Even though the device loading is approximately the same, however, human error can lead to small variance during loading. Our earlier papers show that the EIS spectra of the device are dependent on the device structure 24 . Hence a normalization would allow us to reduce/remove the variation due to the packing.…”

“…NP-µIDE with packed carbon materials increases convective transport, disrupting the diffusive dynamics that govern the EDL. Hence, the EDL capacitor signal moves to higher frequencies 24,25 . These allow the measurement of the EIS sensor signal at significantly higher frequencies reducing the noise and making the system rapid.…”

Metal–Organic Framework-Based Microfluidic Impedance Sensor Platform for Ultrasensitive Detection of Perfluorooctanesulfonate

“…A microfluidic platform consisting of microelectrodes was used to detect the binding of the PFOS to Cr-MIL-101 using electrochemical impedance spectroscopy (EIS). Figure demonstrates the platform assembly consisting of three layers, top and bottom layers of interdigitated microelectrode array (IDμE) and a middle layer consisting of tightly packed Cr-MIL-101, all contained within a microfluidic channel (the detailed procedure of platform assembly is shown in Figure S4 and elsewhere). , An array of IDμEs (width 10 μm and length 500 μm) were used to enhance the signal-to-noise ratio compared to that of macro electrodes; while the reduced electrode size/area here restricts mass transport toward its surface and reduces the signal intensity, an accelerated decrease in power drop and background currents lowers the signal-to-noise ratio at a faster rate, significantly improving the net signal. , Thus, an array of IDμEs has a higher signal-to-noise ratio than a single electrode of the same size. IDμEs as electrochemical transducers offer the added advantages of high collection efficiencies, a low response time that favors rapid detection, low ohmic drop, easy fabrication over multiple substrates, readiness for miniaturization, and eliminates the need for a reference electrode, allowing easy integration with microfluidic chips for multiplexed analytical platforms.…”

“…Moreover, their direct use on a microfluidic lab-on-a-chip sensing platform can offer improved transduction to lower the accessible detection limits and offer unprecedented opportunities for the detection of environmental contaminants . Therefore, in this work, we combine a MOF-based receptor with PFOS affinity with nanoporous ultrasensitive capacitive electrode within a microfluidic flow-through platform , to develop an electrochemical PFOS sensor with high sensitivity, as shown in Scheme .…”