A metafluid with multistable density and internal energy states

Abstract

Investigating and tailoring the thermodynamic properties of different fluids is crucial to many fields. For example, the efficiency, operation range, and environmental safety of applications in energy and refrigeration cycles are highly affected by the properties of the respective available fluids. Here, we suggest combining gas, liquid and multistable elastic capsules to create an artificial fluid with a multitude of stable states. We study, theoretically and experimentally, the suspension’s internal energy, equilibrium pressure-density relations, and their stability for both adiabatic and isothermal processes. We show that the elastic multistability of the capsules endows the fluid with multistable thermodynamic properties, including the ability of capturing and storing energy at standard atmospheric conditions, not found in naturally available fluids.

Multistable Metafluid based Energy Harvesting and Storage

“…This leads to the concept of multistable metafluids, namely artificial suspensions that include a mixture of a standard fluid and architected multistable capsules, engineered to give rise to exceptional thermodynamic properties that extend beyond those of naturally available fluids. [5,27] For example, Epstein et al [28] have designed colloidal particles that rapidly and reversibly snap between two bistable shapes. This shape change occurs inside a fluid by altering its pH, on an extremely short timescale which enables to decouple the particles' shape change from the diffusion-limited stimulus trigger.…”

“…The large choice (of properties) of the liquid background combined with the tunability offered by the metamaterial particles promise relevance to a wide range of applications, from material sensing and bio-detection to energy harvesting and imaging. [29] Recently, Peretz et al [5] studied the steady state thermodynamic properties of a metafluid which was composed of a multitude of multistable gas-filled capsules suspended in a liquid, where each (bi-stable) element of the capsule was comprised of two non-identical conical frusta in opposing orientations. Central to this research was the definition of a permutation, which refers to a state-vector containing the number of the capsule's elements in each of the two phases (open and close) and the spinodal region (partially open).…”

“…Central to this research was the definition of a permutation, which refers to a state-vector containing the number of the capsule's elements in each of the two phases (open and close) and the spinodal region (partially open). We adopt a similar nomenclature in the current study, and while Peretz et al [5] examined the steady state thermodynamics, we here focus on transient energy harvesting processes and the induced flow of the metafluid. To this end, we study a simple, yet practical, case of gas-filled multistable capsules lubricated by an external fluid and contained within a closely-fitted tube.…”

“…These metafluids are created by suspending multistable architected capsules, each enclosing a compressible gas, in a lubricating fluid. [ 5 ] The multistable thermodynamic properties of such metafluids offer new and exciting opportunities for the storage and harvesting of energy. In both refrigeration and heat engine cycles, fluids are transported between hot and cold regions, as well as between high‐ and low‐pressure areas.…”

“…Recently, Peretz et al. [ 5 ] studied the steady state thermodynamic properties of a metafluid which was composed of a multitude of multistable gas‐filled capsules suspended in a liquid, where each (bi‐stable) element of the capsule was comprised of two non‐identical conical frusta in opposing orientations. Central to this research was the definition of a permutation , which refers to a state‐vector containing the number of the capsule's elements in each of the two phases (open and close) and the spinodal region (partially open).…”