Dr Ali Al-Orabi

Ali Al-Orabi

Ali Al-Orabi joined Paunov’s Research Group in 2012, jointly supervised by Prof Panme and Prof Paunov. He graduated with a PhD degree in 2016.

PhD Supervisors: Prof. Nicole Pamme (PI) and Prof. Vesselin N. Paunov (Co-PI)

Research project:

A microfluidic device for the generation and rapid coating of magnetic droplets with polyelectrolytes multilayers

Polymer multilayer capsules (PMLCs) have attracted much attention in diverse areas, such as medicine, catalysis and synthetic chemistry. Conventionally, PMLCs are fabricated by a layer-by-layer (LbL) technique involving the deposition of layers around a template that is itself eventually dissolved, leaving a stable hollow capsule. This process requires many repetitive and time-consuming steps. Here, we report on-chip labeling of magnetic droplets coated with poly(vinylpyrrolidone) (PVP), a surface active polymer, with a layer of negatively-charged poly(acrylic acid) (PAA) polymer, thus reducing the time needed to prepare PMLCs from 1 hour per layer to less than 1 min per layer.

Ali magnetic capsules on chip

Fig. 1. Magnetic emulsion drops are deflected through laminar streams of polyelectrolyte solutions by an external magnet.  Multiple steps of coating and washing are performed as continuous flow process. Two polyelectrolyte layers can be deposited on the magnetic droplet template in less than 1 minute.

Snakes and Ladders chip design for coating of drops of ferrofluid


The video clip shows our Snakes and Ladders chip in action. Magnetic drops are generated and fed into the chip from the LHS of the chip. The channels contains streams of  solutions of polyelectrolyte with alternating charge. A permanent magnet makes the drops to move down the side channels and pass through streams of different polyelectrolyte solutions.  The final result is a Layer-by-Layer coating on the surface of the drops leaving the chip from the RHS. More details in Lab on a Chip, 2017, 17 (2017) 3785 – 3795. doi: 10.1039/c7lc00918f.


1. Alorabi, A.Q., Tarn, M.D., Gómez-Pastora, J., Bringas, E. Ortiz, I.,  Paunov, V.N., Pamme, N.,  On-chip polyelectrolyte coating onto magnetic droplets – towards continuous flow assembly of drug delivery capsulesLab on a Chip, 17 (2017) 3785 – 3795.