Accelerated Ripening in Chemically Fueled Emulsions**

Abstract

Chemically fueled emulsions are solutions with droplets made of phase‐separated molecules that are activated and deactivated by a chemical reaction cycle. These emulsions play a crucial role in biology as a class of membrane‐less organelles. Moreover, theoretical studies show that droplets in these emulsions can evolve to the same size or spontaneously self‐divide when fuel is abundant. All of these exciting properties, i. e., emergence, decay, collective behavior, and self‐division, are pivotal to the functioning of life. However, these theoretical predictions lack experimental systems to test them quantitively. Here, we describe the synthesis of synthetic emulsions formed by a fuel‐driven chemical cycle, and we find a surprising new behavior, i. e., the dynamics of droplet growth is regulated by the kinetics of the fuel‐driven reaction cycle. Consequently, the average volume of these droplets grows orders of magnitude faster compared to Ostwald ripening. Combining experiments and theory, we elucidate the underlying mechanism.

Active Coacervate Droplets Are Protocells That Grow and Resist Ostwald Ripening

“…27 Experimentally, however, active oily droplets coupled to an anhydride formation reaction exhibit accelerated ripening, as the reaction activation/deactivation flux adds to the diffusive flux between droplets. 9 In our experiments with either passive or active coacervate droplets, we did not observe any shrinkage of small droplets, suggesting that Ostwald ripening is being slowed down or prevented by an opposing force closely linked to the nature of our droplets. 28 To understand why these complex coacervate droplets would not show ripening, we consider the balance of (thermodynamic) forces underlying Ostwald ripening.…”

“…3 One of the simplest systems predicted to exhibit growth and division is a droplet coupled to a chemical reaction: by keeping the reaction out of equilibrium (e.g., with a supplied fuel), the droplet can sustain an active behaviour like growth (i.e., an active droplet). [4][5][6][7][8][9] To ensure that the reaction can directly influence behaviour, the droplet must be an open compartment able to exchange material with its surroundings, and compatible with volume change.…”

Molekulare Selbstorganisation 2.0

“…6,7) Beispielsweise lassen sich Größe oder Wachstumsrate der Tröpfchen durch die Kinetik des Reaktionszyklus regulieren. 8) Solche Systeme können Erkenntnisse darüber liefern, wie biologische Assemblierungen reguliert werden. Denn nach wie vor ist unklar, wie eine Zelle die Größe ihrer Organellen kontrolliert.…”

Controlling composition of coexisting phases via molecular transitions

“…The second case refers to a system, where the molecular transitions cannot relax toward thermodynamic equilibrium, i.e., detailed balance of the rates is broken [23,35]. In living or active systems, this is often facilitated by a "fuel" component F which affects the balance between the two molecular states and is, to a good approximation, maintained by chemical reaction cycles [36,37].…”