Figure 3. Ostwald ripening in equilibrium systems. a) The influx Jout→in of molecules P at a drop interface for varying drop radius R and constant supersaturation ∆ (Eq. (5)). The steady state R∗ (J = 0, purple disk) is unstable: drops larger than R∗ grow while smaller ones shrink. Insert: as ∆ decreases, the critical radius R∗ increases. b) Schematic of P concentration profiles along an axis connecting the centres of two drops of different radii R1 > R2. The GibbsThomson relation (Eq. (2)) dictates that the solute concentration is lower close to the large drop (Pout(R1)) than close to the small drop (Pout(R2)). This causes a diffusive flux from small drops to large drops (red arrows, Eq. (5)). c) A multi-drop system is therefore unstable against Ostwald ripening: small drops evaporate and large drops grow. As fewer drops survive the supersaturation ∆ decreases causing more drops to dissolve (see insert in a)). Eventually a unique drop remains in a finite system.
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