Development of an impedance-based interdigitated biochemical sensor using a multiuser silicon process

Abstract

An impedance-based interdigitated biochemical sensor is presented in this work that is designed and fabricated using a standard polycrystalline silicon process. The sensor provides a near real-time, non-invasive, label free and rapid detection technique to quantify chemicals and biomarkers in aqueous solutions. The combination of sensor structure and aqueous solution creates an equivalent electrical circuit comprised of constant and variable capacitive and resistive elements such as solution resistance and double-layer capacitance formed at the interface of the electrodes surface and the solution. The equivalent circuit and its elements are used to quantify the concentration of chemicals in an aqueous solution using the impedance of the system. Diethylhexyl phthalate (DEHP) solution is utilized to characterize and analyze the sensor's response via electrochemical impedance spectroscopy. Finite element analysis and experimental data are used to determine the components of the equivalent circuit. The experimental results show that the sensor is able to detect the concentration of DEHP as low as 0.02 ppm. Using the circuit model and experimental data, the change of doublelayer capacitance and solution resistance of the system for different solution concentrations are obtained. The results show that the double-layer capacitance increases with solution concentration, while the solution resistance decreases. The experimental results also verify the electrical circuit model used for the sensing system.

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“…Figure 7a and Figure 7b show the schematic of different elements in the sensing system and the equivalent circuit associated with them, respectively. In the equivalent electrical circuit, R T1,2 represent the resistance of the transmission lines connetcing the electrodes to the contact pads.C sub1,2 and R sub1,2 are the capacitance and the resistance between the electrodes (including the anchors, transmission line and contact pads) and the substrate [29,36]. R sol is the solution resistance and C dl1,2 and Z W1,2 represent the double-layer capacitance and Warburg impedance at the interface of the two electrodes and the solution, respectively.…”

“…Since these constant parameters do not depend on the solution composition and mainly depend on the sensor structure ( Figure 1b and Figure 1c), they act as parasitic elements and their presence may negatively affect the sensor's response and reduce its sensitivity. The main parasitic parameters are the capacitive and resistive values between the electrodes and the substrate, the resistance value of the transmission lines that connect the devices to the measurement equipment, and the capacitive and resistive values between the transmission line/contact pads and the substrate [28,29].…”

“…The proposed sensor designs have 3D structures where one or both of the sensing electrodes are suspended and the aqueous solution can reach both sides of the electrodes creating a larger electrode-solution interface. It should be noted that it is possible to increase the interface area for conventional IDEs by using larger electrodes, but this also increases the parasitic capacitance/resistance values shown in Figure 1b and capacitance and resistance elements between IDE and glass substrate; and (c) Parasitic capacitance and resistance elements between IDE and silicon substrate [27,29].…”

“…Phthalates are commonly used in food packaging and have a high potential for non-occupational leaching and ingestion into packaged beverages such as bottled water, juice and soda drinks and they are directly absorbed into human body fluids [15]. DEHP solution has been used in the past for characterization of biochemical sensors [15,29]. Low concentrations of the DEHP solution are prepared by first, adding ethanol (2 ppm) to the deionized water as a polar solvent to dissolve DEHP, and then DEHP is added to the distilled water and different concentrations of DEHP solutions, from 0.02 ppm to 10 ppm are prepared for impedance measurements.…”

Fabrication of Electrochemical Influenza Virus (H1N1) Biosensor Composed of Multifunctional DNA Four-Way Junction and Molybdenum Disulfide Hybrid Material

“…CV was performed at a scan rate of 50 mV/s and 0.6–0.1 V. EIS was measured at a frequency range of 100 kHz to 1 Hz with a DC potential of 0.25 V. A 1:1 M ratio of 5 mM [Fe(CN) 6 ] 3−/4− redox repair in 10 mM HEPES (pH 7.04) containing 1 M KCl was used as buffer. The copper probe tips were made to contact the counter electrode and the working electrode [ 33 ]. To confirm clinical usage of the fabricated biosensor, the results of CV and EIS were compared HA (Hemmaglutinin) protein diluted in PBS (Phosphate buffered saline) buffer and HA protein diluted in 10% human serum, respectively.…”