Microfluidics with on-line dynamic light scattering for size measurements

Area of Science:

• Colloid and interface science
• Microfluidics
• Optical measurement techniques

Background:

• On-line measurement of colloidal sizes in microfluidic systems presents challenges due to flow dynamics.
• Poiseuille flow in microchannels can cause Doppler shift interferences, complicating dynamic light scattering (DLS) measurements.

Purpose of the Study:

• To investigate the feasibility of on-line DLS for colloidal size determination in pressure-driven microfluidic flows.
• To develop and experimentally validate a DLS setup integrated with microfluidics for real-time particle sizing.
• To demonstrate applications in mixture viscosity monitoring and nanoparticle co-assembly.

Main Methods:

• Theoretical analysis of DLS in microfluidic flow to identify feasible parameter ranges.
• Construction of a DLS setup coupled with a PDMS-based microfluidic chip.
• Experimental validation of theoretical predictions for Brownian scatterers.

Main Results:

• Theoretical framework established to guide experimental design for on-line DLS.
• Experimental validation of colloidal size estimation in microchannels.
• Development of a microfluidic chip enabling rapid mixing (approx. 200 ms) and subsequent DLS size measurements (approx. 300 ms post-mixing).

Conclusions:

• On-line DLS measurements of colloidal sizes are feasible in microfluidic flows under specific conditions.
• The developed system allows for rapid characterization of microfluidic mixtures.
• Demonstrated applications include continuous viscosity monitoring and electrostatic co-assembly studies.