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Techniques and Facilties

A wide range of experimental techniques are used in our group to investigate the dynamics of liquid flows and the properties of colloidal particles, lipid membrane and liquid interfaces. We also develop new methods to characterise liquid droplets and solid particle properties, such as composition, size, morphology and interfacial tension.

Optical Microscopy

We use bright-field, single- and two-photon excitation fluorescence, confocal and fluorescence life time imaging microscopy to characterise the distribution of fluorescence colloids, the physico-chemical properties of lipid membranes and liquid interfaces, and the structure of multi-functional micro-particles. Digital images processing methods are also used to determine particle physical properties, such, for example, droplet interfacial tension and surfactant monolayer's bending rigidity.

The figure shows our Optical Trapping and Epifluorescence Modular (OTEM) Microscope. The video shows the Brownian motion of fluorescent liposomes in a water solution captured via fast laser-scanning confocal microscopy.

Some of the optical microscopy techniques used by our group were available to us via STFC-funded facility access time grants at the Central Laser Facility of the Rutherford Appleton Laboratory (Harwell Campus, Didcot).

References

R. Al Nuumani et al. (2018) Microfluidic production of poly (1, 6-hexanediol diacrylate)-based polymer microspheres and bifunctional microcapsules with embedded TiO2 nanoparticles. Langmuir, 34, 11822-11831.

G. Bolognesi et al. (2016) Mechanical characterization of ultralow interfacial tension oil-in-water droplets by thermal capillary wave analysis in a microfluidic device. Langmuir, 32, 3580-3586.

Electron Microscopy
Janus_Magnetic_Particles_Langmuir_2020.png
SEM_Grooved_PDMS.png

We use scanning electron microscopy (SEM) to characterise the structure of multi-functional micron-sized particles and the geometry features of our microfluidic devices. Top figure shows SEM image of Janus porous magnetic polymer micro-particles (work in collaboration with Dr Vladisavljevic at Loughborough University). Bottom figure shows the microgrooves on a PDMS substrate.

Reference

N Singh et al. Enhanced accumulation of colloidal particles in microgrooved channels via diffusiophoresis and steady-state electrolyte flows. Langmuir, 2022, 38, 14053-14062.

 

R. Al Nuumani et al. Highly porous magnetic Janus microparticles with asymmetric surface topology. Langmuir, 2020, 36, 12702-12711.

Photo-/Soft-lithography

We have a micro-fabrication station for the manufacturing of bespoken microfluidic devices via standard photo-/soft-lithography techniques. We manufacture microfluidic devices made out PDMS and NOA-81, an optical adhesive glue.

Colloidal Particle Analysis
DLS.png

We use Dynamic Light Scattering (DLS), Electrophoretic Light Scattering (ELS), Nanoparticle Tracking Analysis (NTA) to characterise the size, zeta-pontetial and concentration of nano- and micro-particles. The figure shows the Malvern Zetasizer Advance - Ultra (Red) available at UCL Chemistry for DLS and ELS analysis.

Comsol Multiphysics
ACS_Nano_2021_Simulations.jpeg

Our group uses COMSOL Multiphysics to simulate fluid flows, transport of molecular species and particles and heat transfer in microfluidic systems. The numerical analyses allow us to unveil the physical and chemical mechanisms governing the behaviour of the soft matter systems examined experimentally. 

References

A. Chakra et al. Continuous manipulation and characterization of colloidal beads and liposomes via diffusiophoresis in single-and double-junction microchannels. ACS Nano, 2023, 17, 15, 14644–14657

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