A High-Sensitivity Potentiometric 65-nm CMOS ISFET Sensor for Rapid E. coli Screening

Area of Science:

• Food Safety
• Biosensors
• Microelectronic Sensors

Background:

• Foodborne bacterial infections pose significant threats to public health.
• Potentiometric sensors detect bacteria by measuring pH changes but often suffer from low sensitivity and high costs.
• Existing methods for bacterial detection can be time-consuming.

Purpose of the Study:

• To develop a high-sensitivity, cost-efficient, and miniaturized sensor for detecting foodborne bacteria.
• To improve upon the limitations of traditional potentiometric sensors in terms of sensitivity and cost.
• To establish a rapid and reliable method for prescreening bacterial contamination in food samples.

Main Methods:

• Development of a novel ion-sensitive field-effect transistor (ISFET) sensor using a standard 65-nm complementary metal-oxide-semiconductor (CMOS) process.
• Implementation of a subthreshold pH-to-time-to-voltage conversion scheme to enhance sensor sensitivity.
• Optimization of design parameters including chemical sensing area, transistor size, and discharging time.
• Application of the developed sensor system for the detection of Escherichia coli (E. coli).

Main Results:

• The ISFET sensor achieved an amplified sensitivity of 123.8 mV/pH with a 0.01-pH resolution, significantly outperforming traditional readout structures (6.3 mV/pH).
• The intrinsic sensitivity of the passivation membrane was measured at 33.2 mV/pH.
• The system successfully detected E. coli at densities ranging from 14 to 140 colony-forming units (cfu)/mL.
• A sixfold reduction in screening time was achieved (4 hours) compared to conventional methods (24 hours).

Conclusions:

• The developed ISFET sensor is a high-sensitivity, cost-efficient, and miniaturized solution for food safety applications.
• The proposed subthreshold conversion scheme and optimized design parameters lead to superior performance.
• This portable, time-saving, and low-cost prescreening system demonstrates significant potential for rapid foodborne bacterial detection.