Towards Functional Droplet Architectures: a Belousov-Zhabotinsky Medium for Networks

Abstract

The confluence of droplet-compartmentalised chemical systems and architectures composed of interacting droplets points towards a novel technology mimicking core features of the cellular architecture that dominates biology. A key challenge to achieve such a droplet technology is long-term stability in conjunction with interdroplet communication. Here, we probed the parameter space of the Belousov-Zhabotinsky (BZ) medium, an extensively studied model for non-equilibrium chemical reactions, pipetted as 2.5 mm droplets in hexadecane oil. The presence of asolectin lipids enabled the formation of arrays of contacted BZ droplets, of which the wave patterns were characterised over time. We utilised laser-cut acrylic templates with over 40 linear oil-filled slots in which arrays are formed by pipetting droplets of the desired BZ composition, enabling parallel experiments and automated image analysis. Using variations of conventional malonic acid BZ medium, wave propagation over droplet-droplet interfaces was not observed. However, a BZ medium containing both malonic acid and 1,4-cyclohexanedione was found to enable inter-droplet wave propagation. We anticipate that the chemical excitation properties of this mixed-substrate BZ medium, in combination with the droplet stability of the networks demonstrated here for nearly 400 droplets in a template-defined topology, will facilitate the development of scalable functional droplet networks.

Belousov–Zhabotinsky reaction in liquid marbles

“…Other methods of monitoring the BZ reaction within LMs will be assessed, such as tuning the setup of arrays and taking electrical measurements of the encapsulated BZ solution. Future work will also study changing the chemical composition of the BZ media for example using a mixed 1, 4-cyclohexanedione (CHD)/ malonic acid variant of the reaction [117] or using protic ionic liquids [118]. The mixed CHD/malonic acid system reduced the induction period compared to using CHD only, as well as reducing the gas evolution associated with the malonic acid system.…”

Synthetic tissues

“…A wide variety of receptors are available, from proteins such as bacteriorhodopsin, which can act as a light receptor [32], to completely synthetic receptors, which can respond to various inputs [33,34]. The fast transmission of signals through synthetic tissues can be electrical, as described earlier, while promising alternatives, including mechanical transmission [35] and the propagation of chemical waves [36], remain to be full exploited. In an inventive approach, slow transmission by diffusion from a sender cell, either directly through lipid bilayers or through the α-hemolysin pore, has been used to produce a traveling wave of fluorescence mediated by a gene circuit [37].…”

Multimode Self‐Oscillating Vesicle Transformers

“…[13] Several kinds of synthetic polymer-based self-oscillating supramolecular systems have recently been reported, [14][15][16][17][18] including polymeric fluids, [19] polymer brushes, [20] vesicles, [21,22] microgels, [23] and gels. [24] Among them, self-oscillating vesicles driven by oscillating chemical reactions or other periodical triggers have attracted great interest, [25] as vesicles exhibit close similarity to biomembranes.F or instance,t he group of Yoshida [26][27][28][29] reported vesicles that experienced vesicles/ unimers, [26] swelling/ deswelling, [3] and buckling/unbuckling [27] oscillations driven by aB elousov-Zhabotinsky (B-Z) oscillatory reaction. [28,29] Theg roup of Bastakoti and Perez-Mercader presented the B-Z reaction driving vesicles through polymerization-induced self-assembly.…”