A 12.8 k Current-Mode Velocity-Saturation ISFET Array for On-Chip Real-Time DNA Detection

Area of Science:

• Electronics
• Biotechnology
• Chemical Sensing

Background:

• Current-mode operation of ion-sensitive field-effect transistors (ISFETs) is explored for improved linearity.
• CMOS scaling trends necessitate compatible sensing technologies for integrated systems.

Purpose of the Study:

• To develop and characterize a large-scale CMOS chemical-sensing array for real-time ion imaging and DNA amplification detection.
• To leverage ISFETs in velocity saturation for linear pH-current characteristics.
• To address non-ideal effects in floating gate devices for robust sensing.

Main Methods:

• Implementation of a 12.8k-sensor array using a 0.35-μm CMOS process with 2T per pixel topology.
• Characterization considering pixel mismatch and signal attenuation due to passivation capacitance.
• Utilizing a specific biasing regime to maintain linearity despite device non-idealities.

Main Results:

• Achieved a linear pH-to-current response with a sensitivity of 1.03 μA/pH.
• Demonstrated a pH resolution of 0.101 pH.
• Successfully applied the array for real-time detection of NDM carbapenemase gene in E. coli via loop-mediated isothermal amplification.

Conclusions:

• The developed CMOS chemical-sensing array offers a linear and sensitive platform for real-time biosensing.
• Current-mode ISFET operation in velocity saturation is a viable strategy for scalable, high-performance chemical sensors.
• The system is suitable for rapid genetic detection in clinical and research settings.