FET Switch Nanosecond Fluorescence Signal Detection
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Solution Overview
Problem
Current technologies face challenges in detecting very short decay time fluorescence signals due to limitations in switching speed and signal-to-noise ratio, particularly with high performance probes having lifetimes around 3-4 nanoseconds, where traditional methods result in significant noise and reduced sensitivity.
Innovation Solution
The use of a high-speed switching circuit, specifically a Field Effect Transistor (FET) switch, to selectively direct the desired component of a repetitive signal to the detection mechanism, allowing for precise timing and reduced excitation light interference, thereby improving the signal-to-noise ratio by 'off-gating' the detection process and enabling detection of very short decay time fluorescence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional detection methods are used for short decay time fluorescence, then the detection system is simpler, but the signal-to-noise ratio deteriorates significantly
Solution Approach 1:
The patent applies dynamics by using a high-speed switching circuit (FET switch) that dynamically changes the detection system's state on nanosecond timescales. The switch rapidly alternates between connecting and disconnecting the detection mechanism from the light path, synchronized with the fluorescence decay timing. This dynamic switching enables selective detection of the fluorescence signal while rejecting excitation light, achieving high signal-to-noise ratio for short decay time probes without requiring complex optical filtering systems.
Solution Approach 2:
The patent implements periodic action through the high-speed switching circuit that operates in periodic cycles synchronized with the fluorescence excitation and decay. The FET switch periodically connects the detection mechanism to capture the fluorescence signal during its decay phase, then disconnects to reject subsequent excitation light pulses. This periodic switching at nanosecond frequencies enables temporal separation of signal and noise, achieving superior detection precision for short-lived fluorophores.
2Measurement precision
If high performance fluorescent probes with lifetimes around 3-4 nanoseconds are used, then the detection sensitivity is improved, but the detection difficulty increases due to switching speed requirements
Solution Approach 1:
The patent replaces mechanical or electronic switching systems with insufficient speed using a Field Effect Transistor (FET) switching circuit capable of nanosecond-scale operation. The FET switch provides the necessary switching speed (rise and fall times in the nanosecond range) to track and detect fluorescence signals from high-performance probes with 3-4 nansecond lifetimes. This substitution of the switching mechanism enables the detection of ultra-short decay time fluorophores that were previously undetectable with conventional switching technology.
3Measurement precision
If the detection mechanism remains continuously active, then the detection coverage is complete, but the excitation light interference increases
Solution Approach 1:
The patent extracts or removes the excitation light interference from the detection path by using the high-speed FET switch to disconnect the detection mechanism during excitation light pulses. The switch timing is precisely controlled to be open (disconnecting) during excitation and closed (connecting) during fluorescence decay. This extraction of harmful excitation light from the detection path while maintaining detection coverage during signal emission achieves high signal-to-noise ratio without sacrificing detection completeness.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly enhances the signal-to-noise ratio, allowing for the detection of fluorescence signals with improved sensitivity, even at very low concentrations, such as femtomolar levels, by minimizing excitation light interference and optimizing data collection timing.
Implementation Method 1
The use of a high-speed switching circuit, specifically a Field Effect Transistor (FET) switch, to selectively direct the desired component of a repetitive signal to the detection mechanism
Implementation Method 2
a pulsed light source which excites the fluorophore in the sample
Data Source
AI summary
A device and system for measuring the multidimensional distribution of a sample tagged with a short life fluorescent label. The substance applied to a sample holder can be scanned with an optical point source excitation and read back optical stage. The sample can be excited at each of a plurality of points with a fast, e.g., nanosecond pulse of light. The resulting fluorescence can be detected after the excitation is extinguished. A detection gate window can be optimized to maximize the fluorescence signal detected for a predetermined amount of time.