Fast Active Merging of Microdroplets in Microfluidic Chambers Driven by Photo-Isomerisation of Azobenzene Based Surfactants.

Zain Hayat,Claire Deo,Abdel I El Abed,Juan Xie,Rémi Métivier,Malcolm Buckle,Nizar Bchellaoui,Nicolas Bogliotti

doi:10.3390/bios9040129

Abstract

In this work, we report on the development of a newly synthesized photoactive reversible azobenzene derived surfactant polymer, which enables active and fast control of the merging of microdroplets in microfluidic chambers, driven by a pulsed UV laser optical stimulus and the well known cis-trans photo-isomerisation of azobenzene groups. We show for the first time that merging of microdroplets can be achieved optically based on a photo-isomerization process with a high spatio-temporal resolution. Our results show that the physical process lying behind the merging of microdroplets is not driven by a change in surface activity of the droplet stabilizing surfactant under UV illumination (as originally expected), and they suggest an original mechanism for the merging of droplets based on the well-known opto-mechanical motion of azobenzene molecules triggered by light irradiation.

Highlights

Many lab-on-a-chip (LoC) applications have become possible thanks to the ability to control mixing of different droplet contents, which enabled the sequencing of many complex bio-chemical and biological reactions with a high level of control and flexibility over the last decade; see for a review [1,2,3,4,5,6,7]
Dunkel et al [22] showed that active merging of microdroplets can be achieved optically and very selectively using the photolysis process of photolabile surfactants [22]
We consider a new strategy based on the photo-isomerization process (Figure 1) of a newly synthesized azobenzene derivative surfactant polymer, whose structure is given in Figure 2 and which is named in this study KryAz600, to achieve an active merging of water-in-oil (W/O) microdroplets using a picosecond pulsed UV laser

Summary

Introduction

Many lab-on-a-chip (LoC) applications have become possible thanks to the ability to control mixing of different droplet contents, which enabled the sequencing of many complex bio-chemical and biological reactions with a high level of control and flexibility over the last decade; see for a review [1,2,3,4,5,6,7]. Among all manipulation schemes allowed by droplet-based microfluidics technology [8,9,10,11,12,13,14,15,16], active merging of microdroplets (AMD) is probably one of the most important. It is generally achieved using a high alternating current (AC) voltage [17], or using a direct current (DC) voltage [18]. We consider a new strategy based on the photo-isomerization process (Figure 1) of a newly synthesized azobenzene derivative surfactant polymer, whose structure is given in Figure 2 and which is named in this study KryAz600, to achieve an active merging of water-in-oil (W/O) microdroplets using a picosecond (ps) pulsed UV laser

Methods

Results

Conclusion