A Compact Analog Histogramming SPAD-Based CMOS Chip for Time-Resolved Fluorescence.

Area of Science:

• Photonics and Spectroscopic Analysis
• Integrated Circuit Design
• Biomedical Engineering

Background:

• Time-resolved fluorescence is crucial for substance analysis, but traditional methods using CMOS chips involve post-data acquisition analysis.
• Existing methods can be prone to measurement artifacts, limiting accuracy and speed.

Purpose of the Study:

• To present a novel analog CMOS chip for real-time fluorescence decay time measurement.
• To demonstrate the chip's capability in classifying photons based on arrival times at a CMOS SPAD sensor.
• To explore its potential for developing point-of-care devices.

Main Methods:

• Fabrication of an analog CMOS chip using a 1P6M 0.18 μm HV-CMOS process.
• Implementation of tailored slice timings (168 ps to 4.9 ns) and 9 timing windows per pixel.
• Integration of the chip with excitation light and a microfluidic chip for practical application.

Main Results:

• The chip successfully divides fluorescence decay time into slices and classifies photons in real-time.
• Each pixel features 9 timing windows with 13-bit counts and high resolution.
• The system demonstrated the ability to determine quantum dot decay times in minute solution volumes (20 nl).

Conclusions:

• The developed analog CMOS chip offers a powerful, artifact-reducing approach for time-resolved fluorescence measurements.
• This technology has significant potential for the development of compact, point-of-care diagnostic devices.
• The real-time photon classification capability enhances analytical speed and accuracy.