The design, construction and control of artificial self-organized systems modelled on dynamical behaviours of living systems are important issues in biologically inspired engineering. Such systems are usually based on complex reaction dynamics far from equilibrium; therefore, the control of non-equilibrium conditions is required. Here we report a droplet open-reactor system, based on droplet fusion and fission, that achieves dynamical control over chemical fluxes into/out of the reactor for chemical reactions far from equilibrium. We mathematically reveal that the control mechanism is formulated as pulse-density modulation control of the fusion–fission timing. We produce the droplet open-reactor system using microfluidic technologies and then perform external control and autonomous feedback control over autocatalytic chemical oscillation reactions far from equilibrium. We believe that this system will be valuable for the dynamical control over self-organized phenomena far from equilibrium in chemical and biomedical studies.

Recently, micrometer-sized bacterial culture systems have attracted attention as useful tools for synthetic biology studies. Here, we present the development of a bacterial continuous culture system based on a microdroplet open reactor consisting of two types of water-in-oil microdroplets with diameters of several hundred micrometers. A continuous culture was realized the through supply of nutrient substrates and the removal of waste and excess bacterial cells based on repeated fusion and fission of droplets. The growth dynamics was controlled by the interval of fusion. We constructed a microfluidic system and quantitatively assessed the dynamics of the bacterial growth using a mathematical model. This system will facilitate the study of synthetic biology and metabolic engineering in the future.

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Recently, synthetic biology based on constructive approaches, such as genetically engineering of living cells, has attracted attention. For genetic engineering, culturing living cells in a steady condition is required, and chemostats based on inflow and outflow of culture media are often used. However, it is difficult to observe a cell while culturing because chemostats require large volume of media (>0.1 L-). In this study, to conquer this problem, we propose a microfluidic chemostat based on water-in-oil microdroplets. The inflow and outflow of media are controlled by droplet fusion and fission. We formulated a numerical model and investigated it by simulations. We believe that this chemostat can be applied to single-cell observation and promote synthetic biology.