Self-oscillating coacervates: a built-in chemical clock sustains membraneless protocell populations

Abstract Coacervates formed by liquid–liquid phase separation are compelling protocell models because they provide a membrane-free, minimal form of compartmentalisation¹,². Their intrinsic liquid nature, however, promotes coalescence and Ostwald ripening that erase individuality on minute-to-hour timescales³. Because these instabilities are kinetic, sustaining coacervate populations may require an explicit time-based route. Existing strategies rely on static barriers such as membranes⁴ or negative feedback loops⁵, yet they lack a general framework for time-programmed control of phase separation. Here we show that a chemical clock sustains coacervate populations by imposing periodic, time-limited control of phase separation. We demonstrate that time-limited alternation of growth-permitting and dissolution-enforcing phases sustains coacervate populations near steady state over many cycles. This control manifests as recurrent emergence, coalescence and dissolution regimes whose schedule is controlled by the internal Belousov–Zhabotinsky chemical clock. When the clock is exhausted, regulation fails and uncontrolled coarsening resumes, underscoring the causal role of time-programmed control. These results provide proof of a design principle in which a chemical clock imposing periodic, time-limited modulation of phase separation sustains coacervate populations, and they open avenues to a class of time-programmed membraneless protocell models.