Fig. 2.

Bulging profile $\psi$ of thin skin of an elastic film embedded with liquid-filled channels. (A) Curves 1–7 represent liquids: (1) acetonitrile (filled-in channel of diameter $d=450$ µm, embedded in film of thickness $h=467$ µm and minimum skin thickness, $t_0=17$ µm); (2) nitromethane ($d=450$ µm, $h=480$ µm, and $t_0=30$ µm); (3) DMSO ($d=180$ µm, $h=185$ µm, and $t_0=5$ µm); (4) perflurooctane, ($d=180$ µm, $h=204$ µm, and $t_0=24$ µm); (5 and 6) ethylene glycol, air ($d=450$ µm, $h=468$ µm, and $t_0=18$ µm); and (7) water ($d=450$ µm, $h=480$ µm, and $t_0=30$ µm), respectively. (B) Two liquids are injected alternatively into the channel. Bulging deflection $\psi$ of the channel skin flips from 1 to 1′ as nitromethane, initially present in the channel, is replaced by injecting water into it. The profile flips back to 2 as water is similarly replaced by nitromethane. This process is repeated 4–5 times, without any signature of irreversibility or hysteresis. A film embedded with channel of diameter $d=550$ µm and minimum skin thickness $t=35$ µm is used in this experiment.