Spontaneous assembly of chemically encoded two-dimensional coacervate droplet arrays by acoustic wave patterning.

Liangfei Tian,Mei Li,Bruce W Drinkwater,Philip G Bassindale,Adrian Barnes,Avinash J Patil,Stephen Mann,Nicolas Martin

doi:10.1038/ncomms13068

Abstract

The spontaneous assembly of chemically encoded, molecularly crowded, water-rich micro-droplets into periodic defect-free two-dimensional arrays is achieved in aqueous media by a combination of an acoustic standing wave pressure field and in situ complex coacervation. Acoustically mediated coalescence of primary droplets generates single-droplet per node micro-arrays that exhibit variable surface-attachment properties, spontaneously uptake dyes, enzymes and particles, and display spatial and time-dependent fluorescence outputs when exposed to a reactant diffusion gradient. In addition, coacervate droplet arrays exhibiting dynamical behaviour and exchange of matter are prepared by inhibiting coalescence to produce acoustically trapped lattices of droplet clusters that display fast and reversible changes in shape and spatial configuration in direct response to modulations in the acoustic frequencies and fields. Our results offer a novel route to the design and construction of ‘water-in-water' micro-droplet arrays with controllable spatial organization, programmable signalling pathways and higher order collective behaviour.

Highlights

The spontaneous assembly of chemically encoded, molecularly crowded, water-rich micro-droplets into periodic defect-free two-dimensional arrays is achieved in aqueous media by a combination of an acoustic standing wave pressure field and in situ complex coacervation
The droplets are stabilized by immersion in an appropriate continuous phase or exposure on a dry surface, which lead to patterns of physically isolated droplets, which can be exploited as independent micro-reactors that are essentially free from cross-contamination
Using an acoustic standing wave trap, we demonstrate the spontaneous assembly and organization of polydiallydimethylammonium chloride (PDDA)/adenosine 5/-triphosphate (ATP) coacervate micro-droplets into defect-free arrays with controllable lattice spacing and droplet size

Summary

Introduction

The spontaneous assembly of chemically encoded, molecularly crowded, water-rich micro-droplets into periodic defect-free two-dimensional arrays is achieved in aqueous media by a combination of an acoustic standing wave pressure field and in situ complex coacervation. Isolation of the droplets within the arrays is not compatible with dynamical interactions such as triggering chemical signals between the droplets or enabling the droplets to communicate with and respond to time-dependent changes in their external environment To achieve these dynamical interactions, new technologies are required that provide the production and organization of liquid micro-droplets with similar polarity to the associated continuous phase, such as the formation and patterning of water-rich droplets in a continuous aqueous phase. We show that it is possible to transit a reaction wavefront through an array of acoustically trapped enzyme-containing coacervate micro-droplets by establishing an appropriate chemical gradient within the sample chamber of the device

Methods

Results

Conclusion