Fig. 4: Pressure cycles and experimental demonstration.
From: A metafluid with multistable density and internal energy states
a Experimental and theoretical pressure (p/patm) vs. density (ρ/ρ0) cycles. The black, blue, and red curves represent (analytically calculated) equi-permutation lines, loading, and unloading modes, respectively. Orange and green curves represent the experimental results (each curve containing three cycles). Representative frames (circular insets) taken from our experiment correspond to points (1)–(4) on the orange curve. In the experimental data, snap-open and snap-close points are (\({v}_{{{{{{\mathrm{s}}}}}}}^{{{\mbox{I}}}},{p}_{{{{{{\mathrm{s}}}}}}}^{{{\mbox{open}}}}\)) = (0.26 ml, 26.24 kPa) and (\({v}_{{{{{{\mathrm{s}}}}}}}^{{{\mbox{II}}}},{p}_{{{{{{\mathrm{s}}}}}}}^{{{\mbox{close}}}}\)) = (1.04 ml, −16.61 kPa), respectively. The slopes of the tri-linear approximation are kI = 2300 kPa ml−1, kII = 152 kPa ml−1, for phase I and II, respectively, and the number of bi-stable elements per capsule is 18. b The corresponding internal energy of the system, where points (1–4) correspond to the frames in a. c Experimental setup: the pressure controller, which is responsible for regulating the (constant) pressure in the fluid reservoir, is connected to the metafluid tank inlet via a flow valve. The height of the fluid in the fluid reservoir is monitored in the experiment to allow measuring the change in equivalent density of the metafluid. See Supplementary Movies 1–2.
