Monodisperse emulsions from a microfluidic device, characterised by diffusion NMR

Area of Science:

• Colloid and Surface Science
• Materials Science
• Analytical Chemistry

Background:

• Microfluidic devices offer precise control over emulsion formation.
• Characterizing droplet size and distribution is crucial for emulsion applications.
• Nuclear Magnetic Resonance (NMR) spectroscopy provides insights into molecular dynamics and structure.

Purpose of the Study:

• To develop a microfluidic method for generating monodisperse polymeric oil-in-water emulsions.
• To utilize pulse field gradient nuclear magnetic resonance (PFG-NMR) for droplet size and polydispersity determination.
• To investigate the influence of restricted diffusion on PFG-NMR signal attenuation.

Main Methods:

• Fabrication of a microfluidic device for emulsion generation.
• Application of pulse field gradient nuclear magnetic resonance (PFG-NMR) spectroscopy.
• Analysis of PFG-NMR signal attenuation using diffusion equation models.
• Comparison of NMR-derived sizes with optical microscopy and laser diffraction.

Main Results:

• Successful creation of monodisperse polymeric oil-in-water emulsions (15-100 µm).
• PFG-NMR signal minima enabled straightforward calculation of droplet size and polydispersity.
• Restricted diffusion within droplets was confirmed and analyzed.
• Water NMR provided structural information on the continuous phase.

Conclusions:

• Microfluidics is an effective tool for producing well-defined polymeric emulsions.
• PFG-NMR is a powerful, non-invasive technique for characterizing emulsion droplet size and polydispersity.
• Understanding diffusion dynamics is key to interpreting PFG-NMR data for emulsions.