A CMOS Pixelated Nanocapacitor Biosensor Platform for High-Frequency Impedance Spectroscopy and Imaging

Area of Science:

• Electrical Engineering
• Biotechnology
• Materials Science

Background:

• The Debye screening limit restricts biosensor performance in physiological salt concentrations.
• Existing label-free biosensing platforms often struggle with sensitivity and specificity in complex biological fluids.

Purpose of the Study:

• To develop a fully electronic, label-free, and temperature-controlled biosensing platform.
• To overcome the Debye screening limit across a broad range of electrolyte concentrations.
• To enable quantitative detection of analytes beyond the electrical double layer.

Main Methods:

• Utilized a 90-nm CMOS-integrated circuit with a nanocapacitor array and readout circuitry.
• Integrated a field-programmable gate array (FPGA) interface with a soft processor for data acquisition.
• Implemented chip processing, microfluidics, temperature control, and calibration procedures.
• Performed capacitance spectroscopy up to 70 MHz and finite element method (FEM) simulations.

Main Results:

• Demonstrated high-frequency operation (up to 70 MHz) to surpass the Debye screening limit.
• Achieved quantitative capacitance spectra measurements, enabling detailed analyte characterization.
• Validated sensor performance against FEM numerical simulations using Poisson-Drift-Diffusion formalism.
• Showcased the platform's ability to detect events beyond the electrical double layer.

Conclusions:

• The developed biosensing platform offers a robust solution for label-free detection in diverse electrolyte conditions.
• The high-frequency operation and quantitative measurements provide new insights into analyte properties.
• The scalable design allows for broad applicability in both biological and non-biological sensing, such as gas sensing.