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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 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. By combining experimental analysis and numerical simulations, we discovered solute-driven transport mechanisms for the reversible trapping and accumulation of particles within dead-end pores and for the focusing of particles within straight open channels under continuous flow settings. We developed proof-of-concept microdevices that exploit these mechanisms for the continuous size-based separation and size detection of nanobeads as well as for the measurement of zeta potential and charged lipid composition of small unilamellar vesicles (SUVs).


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


N. Singh et al. (2020). Reversible trapping of colloids in microgrooved channels via diffusiophoresis under steady-state solute gradients. Physical Review Letters, 125,  248002.

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


A. Chakra et al. (2023). Continuous manipulation and characterization of colloidal beads and liposomes via diffusiophoresis in single-and double-junction microchannels. arXiv preprint arXiv:2302.05800. 

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)


G. Bolognesi et al. (2018). Sculpting and fusing biomimetic vesicle networks using optical tweezers. Nature communications, 9, 1882.

M.S. Friddin et al. (2019) Direct manipulation of liquid ordered lipid membrane domains using optical traps. Communications Chemistry, 2, 6.

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