Microfluidic Manipulation

We adopt various strategies to manipulate single particles or groups of particles in a microfluidic environment to investigate fundamental properties and behaviour of flows and soft matter systems as well as to develop new methods for microfluidic particles processing applications, such as particle filtration, sorting, trapping and accumulation.

Diffusiophoresis

Diffusiophoresis is a phoretic transport phenomenon in which the chemical energy stored in the form of solute concentration gradient is transduced into particle motion. Diffusiophoresis offer several advantages for microfludic applications, such as i) absence of external energy input for directing particles, ii) selectivity based on particle size and charge, iii) cost effectiveness due to the lack of costly/bulky equipment. Our group investigates new approaches to apply diffusiophoresis for particle processing operation in microfluidic devices.

 

Collaborators: Dr Francois Nadal (Loughborough University), Dr Christophe Pirat and Dr Cecile Cottin-Bizonne (University of Lyon 1)

Optical Tweezers

A tightly-focussed laser beam can trap micron-sized objects, like droplets and particles, near the focus of the beam. By stirring the laser beam, the trapped object can be positioned within the sample working volume with high temporal and spatial resolution. Optical tweezers can also be used to quantify the force exerted on the trapped object with sub-pN resolution. Our group uses optical tweezers to investigate the physical and chemical properties of soft matter system, such as liquid interfaces with ultralow interfacial tension and lipid membranes. We also use optical tweezers to build bio-mimetic structures, including flexible nanotubes and drop/vesicle assemblies, with a bottom-up approach for synthetic biology applications.

Collaborators: Dr Andy Ward (STFC), Dr Arwen Tyler (University of Leeds),  Dr Buddhapriya Chakrabarti (University of Sheffield), Prof. Colin Bain (Durham University), Dr Yuval Elani and Prof. Oscar Ces (Imperial College London)

References

G. Bolognesi, M.S. Friddin, A. Salehi-Reyhani, N.E. Barlow, N.J., Brooks, O. Ces, Y. Elani (2018).  Nature communications, 9, 1882.

G. Bolognesi, M.S. Friddin, A. Salehi-Reyhani, N.E. Barlow, N.J., Brooks, O. Ces, Y. Elani (2018).  Nature communications, 9, 1882.

 

Microfluidic Processing

We use a range of downstream processing methods to manufacture functional particles for healthcare, food and energy applicatons

Solvent Evaporation

Solvent evaporation is a simple way for producing particles from droplets containing a mixture of polymer(s) and volatile organic solvent.  Such method allows to achieve particle size much smaller than the original droplet size.

We evaporate solvent from droplets to convert them into structured particles. We can also combine solvent evaporation with phase-separation to spatially segregate polymers and produce particles with complex morphologies, such as patchy particles, Janus Particles, golf-ball like particles.

Reference

E.E. Ekanem, S.A. Nabavi, G.T. Vladisavljević, S. Gu, 2015. ACS Applied Materials & Interfaces, 7, 23132.

Ionic Cross Linking

We use ionic cross-linking to generate hydrogel particles from natural bio-materials, such as chitosan and alginate. We can achieve cross-linking off chip, like shown in the figure, or inside microfluidic device by controlled diffusion of acid from continuous phase into the droplets.

Collaborators: Prof. Roland Zengerle (University of Freigurb)

Reference

D. Mark, S. Haeberle, R. Zengerle, J. Ducree, G.T. Vladisavljević, 2009. Journal of Colloid and Interface Science, 336, 634 .

Photo-polymerisation

Photo-polymerisation is based on illuminating mixture of monomer, cross-linker and initiator by UV light which causes the conversion of photo-initiator into a free radical and polymerisation reaction. We use on-the-fly photo-polymerisation in microfluidic devices to cure monomer droplets and convert them in monodisperse particles, like acrylic micro-capsules shown in this image. 

Reference

R. Al Nuumani, G. Bolognesi, G. and G.T. Vladisavljevic, 2018. Langmuir, 34, 11822-11831.

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