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Updated: Jul 27, 2026

Automated System for Single Molecule Fluorescence Measurements of Surface-immobilized Biomolecules
Published on: November 2, 2009
Spatial two-photon fluorescence cross-correlation spectroscopy for controlling molecular transport in microfluidic
Petra S Dittrich1, Petra Schwille
1Experimental Biophysics Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
Fluorescence correlation spectroscopy (FCS) precisely measures microfluidic flow parameters like velocity and direction. This single-molecule spectroscopy technique offers sensitive, non-invasive analysis for microfluidic systems.
Area of Science:
- Microfluidics
- Spectroscopy
- Biophysics
Background:
- Microfluidic systems require precise flow parameter determination for chemical and biochemical processes.
- Fluorescence analysis offers sensitive, non-invasive readout for fluid and particle manipulation.
- Single-molecule detection is crucial for analyzing processes in microscale environments.
Purpose of the Study:
- To present fluorescence correlation spectroscopy (FCS) for determining flow parameters in microstructured channels.
- To explore different FCS modes, including auto- and dual-beam cross-correlation with one- and two-photon excitation.
- To demonstrate the application of FCS in microfluidic systems.
Main Methods:
- Utilizing fluorescence correlation spectroscopy (FCS) with confocal optical setups.
- Employing one- and two-photon excitation techniques for fluorescence analysis.
- Comparing auto-correlation and dual-beam cross-correlation methods for flow dynamics.
Main Results:
- FCS accurately determines microfluidic flow velocity and direction.
- Two-photon excitation enhances measurements in microchannels due to restricted detection volumes and low background.
- Dual-beam cross-correlation distinguishes flow direction and mitigates photophysical artifacts.
Conclusions:
- FCS is a powerful tool for characterizing microfluidic flow dynamics.
- Time-gated two-photon excitation in dual-beam mode improves measurement accuracy.
- FCS applications include microfluidic sorting unit calibration and flow profiling.
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