Modification of the properties of a liquid mixture

Abstract

A system for controlling liquid flow includes a conduit, a field generating element, a flow sensor and control circuitry. The conduit conveys a mixed liquid comprising two or more at least partially miscible component liquids. The field generating element generates an electric field in the mixed liquid in a direction transverse to a flow of the mixed liquid in the conduit. The intensity of the electric field controls a reversible formation of a layer of one of the component liquids along a surface of the conduit. The flow sensor senses the flow rate of the liquid flow in the conduit. The control circuitry controls the field generating element to produce the electric field at an intensity yielding a desired flow rate of the mixed liquid based on flow rate data provided by the flow sensor.

Description

[0001] MODIFICATION OF THE PROPERTIES OF A LIQUID MIXTURE

[0002] TECHNOLOGICAL FIELD

[0003] The present disclosure, in some embodiments, thereof, relates to the properties of confined liquids, and, more particularly, but not exclusively, to the properties of confined mixtures of liquids.

[0004] BACKGROUND

[0005] The confinement of liquids by solid surfaces is a fundamental aspect of both everyday life and industrial processes. The dynamics of liquid flow within these confined spaces are crucial, as they significantly impact the efficiency and effectiveness of fluid transport systems. Whether liquids are flowing through household devices, industrial pipelines, or microfluidic channels, the interaction between the liquid and the solid surfaces dictates flow characteristics, such as velocity, pressure, and turbulence.

[0006] Effective management of liquid flow is significant for ensuring smooth and consistent operation of some systems with conduits for liquid flow, minimizing energy usage, and reducing wear and tear on system components, and optimizing liquid delivery through the conduit.

[0007] SUMMARY OF THE INVENTION

[0008] Some embodiments of the invention relate to using an electric field to affect the composition of component liquids within a mixed liquid.

[0009] The mixed liquid includes constituents (also denoted component liquids). The component liquids are partially or completely miscible. In the absence of an electric field the composition of the component liquids in the mixed liquid is typically homogeneous.

[0010] When an electric field is generated in the mixed liquid, the electric field couples differently to the component liquids. The composition of the component liquids due to their different polarity and / or different ability to solvate ions in the mixed liquid becomes non- homogeneous, with one or some of the component liquids being attracted more strongly to an enclosing surface (e.g. the walls of the conduit or inner surface of the cell). In some cases the components of the mixed liquid may separate, forming a layer of one of the component liquids along the enclosing surface.

[0011] Some examples of the instant disclosure present a system and method for controlling the flow of a mixed liquid in a conduit by generating an electric field in the mixed liquid. When the component liquid attracted to the conduit’s inner surface is less viscous than the mixed liquid (and / or other component liquids), the flow rate may increase. Reducing the electric field’s intensity or eliminating it completely may decrease the flow rate in the conduit. This provides a way to control liquid flow in conduit by the use of an electric field. A corresponding but opposite effect occurs when the component liquid attracted to the conduit’s inner surface is more viscous than the mixed liquid (and / or other component liquids). In this case, generating an electric field in the liquid may slow liquid flow in the conduit.

[0012] Some other examples of the instant disclosure present a system and method for controlling a physical property of a cell containing a mixed liquid. When an electric field is generated in the cell the composition of the component liquids within the cell becomes non-uniform, thus changing a physical property of the entire cell. Examples of physical properties which may be controlled by generating an electrical field in a mixed liquid may include but are not limited to the electrical conductivity of the cell, the permittivity of the cell or the thermal conductivity of the cell.

[0013] According to a first aspect of some embodiments of the present disclosure there is provided a system for controlling liquid flow. The system includes: a conduit configured for conveying a mixed liquid comprising a plurality of at least partially miscible liquids; a field generating element, configured for generating an electric field in the mixed liquid in a direction transverse to a flow of the mixed liquid in the conduit, wherein an intensity of the electric field controls a reversible formation of a layer of one of the plurality of at least partially miscible liquids along a surface of the conduit; a flow sensor associated with the conduit, configured for sensing a flow rate of the liquid flow in the conduit; and a control circuitry associated with the field generating element and the flow sensor, configured for controlling the field generating element to produce the electric field at an intensity yielding a desired flow rate of the mixed liquid based on flow rate data provided by the flow sensor.

[0014] According to some embodiments of the present disclosure, the control circuitry is further configured to calculate an electrical field intensity sufficient to induce a separation of the mixed liquid to a degree yielding the desired flow rate.

[0015] According to some embodiments of the present disclosure, the calculating is based on at least one of: a. respective viscosities of the at least partially miscible liquids; b. respective polarities of the at least partially miscible liquids; c. respective levels of miscibility of the at least partially miscible liquids; d. relative proportions of the at least partially miscible liquids in the mixed liquid; e. a temperature of the mixed liquid, f. the amount of charge carriers in the mixture; g. the amount of dissolved salt in the mixture; and h. the ambient temperature.

[0016] According to some embodiments of the present disclosure, the field generating element includes at least two conductive electrodes on respective sides of the conduit, and are connected to a power source. The electrodes may have any shape that enables it to create the transverse electric field (e.g. from wire-like to patch-like).

[0017] Optionally, the field generator electrodes are covered by an insulating material (e.g. glue, tape, other plastic material, etc.).

[0018] According to some embodiments of the present disclosure, the field generating element includes an electric field generator.

[0019] According to some embodiments of the present disclosure, the field generating element includes a magnetic field generator configured to generate a magnetic field that induces the electric field in the mixed liquid in the direction transverse to the liquid flow direction.

[0020] According to some embodiments of the present disclosure, the electrical field is perpendicular to the direction of flow of the mixed liquid. According to some embodiments of the present disclosure, the at least partially miscible liquids have different respective polarities and different respective viscosities.

[0021] According to some embodiments of the present disclosure, the liquid forming the layer along the surface has a lower viscosity than the other liquids in the mixed liquid, such that generating the electric field increases liquid flow through the conduit.

[0022] According to some embodiments of the present disclosure, the liquid forming the layer along the surface has a higher viscosity than the other liquids in the mixed liquid, such that generating the electric field decreases liquid flow through the conduit.

[0023] According to some embodiments of the present disclosure, the system further includes a temperature control element configured to maintain the mixed liquid at a temperature at which the layer forms along the surface of the conduit when the electric field is generated across the conduit.

[0024] According to some embodiments of the present disclosure, the system further includes a pump configured to create a pressure differential along the conduit, so as to cause the mixed liquid to flow through the conduit.

[0025] According to some embodiments of the present disclosure, the system further includes a container configured for containing the mixed liquid and providing the mixed liquid to a conduit inlet.

[0026] According to some embodiments of the present disclosure, the conduit include a pipe.

[0027] According to some embodiments of the present disclosure, the conduit includes a channel.

[0028] According to some embodiments of the present disclosure, the conduit is a supply line in one of an inkjet print cartridge or paint spray device.

[0029] According to some embodiments of the present disclosure, the conduit is configured to convey a mixture which includes at least one petroleum product and at least one polar liquid.

[0030] According to some embodiments of the present disclosure, the conduit is a component of a microfluidic device and is configured to transport mixed liquids.

[0031] According to some embodiments of the present disclosure, the mixed liquid is one of: a. a mixture of water and at least one petroleum product; b. a mixture of water and glycerol; c. a mixture of water and alcohol; d. a plurality of polar liquids; e. a mixture of at least one polar liquid and at least one nonpolar liquid; and f. a polymer solution.

[0032] According to some embodiments of the present disclosure, the flow sensor includes at least one of: g. an optical flow detector; h. a differential pressure flow meter; i. a Venturi flow meter; j . an ultrasonic flow meter; and k. an electromagnetic flow meter.

[0033] According to a second aspect of some embodiments of the present disclosure there is provided a method for controlling liquid flow. The method includes: generating an electric field in a mixed liquid comprising a plurality of at least partially miscible liquids in a direction transverse to a flow of the mixed liquid through a conduit and at an intensity sufficient to induce the mixed liquid to separate at least partially, so that one of the plurality of at least partially miscible liquids forms a layer along a surface of the conduit; and controlling an intensity of the electric field to yield a desired flow rate of the mixed liquid, based on flow rate data provided by a flow sensor.

[0034] According to some embodiments of the present disclosure, the intensity of the electric field yielding the desired flow rate of the liquid is calculated based on at least one of: a. respective viscosities of the at least partially miscible liquids; b. respective polarities of the at least partially miscible liquids; c. respective levels of miscibility of the at least partially miscible liquids; d. relative proportions of the at least partially miscible liquids in the mixed liquid; e. a temperature of the mixed liquid, f. the amount of charge carriers in the mixture; g. the amount of dissolved salt in the mixture; and h. the ambient temperature.

[0035] According to some embodiments of the present disclosure, the electric field is generated by at least two conductive electrodes on respective sides of the conduit, and are connected to a power source. The electrode may have any shape that enables it to create the transverse electric field (e.g. from wire-like to patch-like).

[0036] Optionally, the field generator electrodes are covered by an insulating material (e.g. glue, tape, other plastic material, etc.).

[0037] According to some embodiments of the present disclosure, the electric field is generated by an electric field generator.

[0038] According to some embodiments of the present disclosure, the electric field is generated by a magnetic field generator configured to generate a magnetic field that induces the electric field in the mixed liquid in the direction transverse to the liquid flow direction.

[0039] According to some embodiments of the present disclosure, the electrical field is perpendicular to the direction of flow of the mixed liquid.

[0040] According to some embodiments of the present disclosure, at least partially miscible liquids have different respective polarities and different respective viscosities.

[0041] According to some embodiments of the present disclosure, the liquid forming the layer along the surface has a lower viscosity than the other liquids in the mixed liquid, such that generating the electric field increases liquid flow through the conduit.

[0042] According to some embodiments of the present disclosure, liquid forming the layer along the surface has a higher viscosity than the other liquids in the mixed liquid, such that generating the electric field decreases liquid flow through the conduit.

[0043] According to some embodiments of the present disclosure, the method further includes maintaining the mixed liquid at a temperature at which the layer forms along the surface of the conduit when the electric field is generated across the conduit. According to some embodiments of the present disclosure, the method further includes creating a pressure differential along the conduit, so as to cause the mixed liquid to flow through the conduit.

[0044] According to some embodiments of the present disclosure, the conduit includes a pipe.

[0045] According to some embodiments of the present disclosure, the conduit includes a channel.

[0046] According to some embodiments of the present disclosure, the conduit is a supply line in one of an inkjet print cartridge or paint spray device.

[0047] According to some embodiments of the present disclosure, the conduit is configured to convey a mixture which includes at least one petroleum product and at least one polar liquid.

[0048] According to some embodiments of the present disclosure, the conduit is a component of a microfluidic device.

[0049] According to some embodiments of the present disclosure, the mixed liquid is one of: a. a mixture of water and at least one petroleum product; b. a mixture of water and glycerol; c. a mixture of water and alcohol; d. a plurality of polar liquids; e. a mixture of at least one polar liquid and at least one nonpolar liquid; and f. a polymer solution.

[0050] According to a third aspect of some embodiments of the present disclosure there is provided a system for controlling a physical property of a cell containing a mixed liquid. The system includes: a field generating element, configured for generating an electric field in a cell containing a mixed liquid, the mixed liquid comprising a plurality of at least partially miscible liquids, at least two of the plurality of at least partially miscible liquids having different respective values of a same physical property, wherein an intensity of the electric field controls a reversible transition of a composition of the plurality of at least partially miscible liquids in the mixed liquid from a uniform composition to a non- uniform composition, and wherein a value of the physical property for the cell is different for the uniform and non-uniform compositions; and a control circuitry associated with the field generating element, configured for controlling the field generating element to produce the electric field at an intensity yielding a desired composition of the plurality of at least partially miscible liquids in the mixed liquid, wherein the physical property is at least one of: an electrical conductivity between two locations on the cell, a permittivity between two locations on the cell, or a thermal conductivity between two locations on the cell.

[0051] According to some embodiments of the present disclosure, the electric field causes at least partial separation of the at least partially miscible liquids within the cell, and the control circuitry is configured to calculate an electrical field intensity sufficient to induce the mixed liquid to separate to a degree yielding a desired value of the physical property.

[0052] According to some embodiments of the present disclosure, the calculating is based on at least one of: a. respective conductivities of the at least partially miscible liquids; b. respective viscosities of the at least partially miscible liquids; c. respective polarities of the at least partially miscible liquids; d. miscibility level of the at least partially miscible liquids; e. relative proportions of the at least partially miscible liquids in the mixed liquid; f. a temperature of the mixed liquid, g. the amount of charge carriers in the mixture; h. the amount of dissolved salt in the mixture; and i. the ambient temperature.

[0053] According to some embodiments of the present disclosure, the physical property is electrical conductivity, such that the cell has a controllable electrical conductivity between the locations. According to some embodiments of the present disclosure, the physical property is permittivity, such that the cell has a controllable permittivity between the locations.

[0054] According to some embodiments of the present disclosure, the physical property is thermal conductivity, such that the cell has a controllable thermal conductivity between the locations.

[0055] According to some embodiments of the present disclosure, the field generating element includes at least two conductive electrodes on respective sides of the conduit, and are connected to a power source. The electrodes may have any shape that enables it to generate the transverse electric field (e.g. from wire-like to patch-like).

[0056] Optionally, the field generator electrodes are covered by an insulating material (e.g. glue, tape, other plastic material, etc.).

[0057] According to some embodiments of the present disclosure, the field generating element includes a magnetic field generator configured to generate a magnetic field that induces the electric field in the mixed liquid.

[0058] According to some embodiments of the present disclosure, the field generating element includes an electric field generator.

[0059] According to some embodiments of the present disclosure, the system is configured for modifying a lubrication layer of a microfluidic device.

[0060] According to a fourth aspect of some embodiments of the present disclosure there is provided a method for controlling a physical property of a cell. The method includes: generating an electric field in a cell containing a mixed liquid, the mixed liquid comprising a plurality of at least partially miscible liquids, at least two of the plurality of at least partially miscible liquids having different respective values of a same physical property, wherein an intensity of the electric field controls a reversible transition of a composition of the plurality of at least partially miscible liquids in the mixed liquid from a uniform composition to a non-uniform composition, and wherein a value of the physical property for the cell is different for the uniform and non-uniform compositions; and controlling the intensity of the electric field so as to obtain a desired composition of the plurality of at least partially miscible liquids in the mixed liquid, wherein the physical property is at least one of: an electrical conductivity between two locations on the cell, a permittivity between two locations on the cell, or a thermal conductivity between two locations on the cell.

[0061] According to some embodiments of the present disclosure, the physical property is electrical conductivity, such that the cell has a controllable electrical conductivity between at least two electrical conductors (e.g. electrodes, wires... ) which are electrically connected to respective locations on the cell.

[0062] According to some embodiments of the present disclosure, the physical property comprises permittivity, such that the cell has a controllable electrical conductivity between the locations.

[0063] According to some embodiments of the present disclosure, in the conductivity is thermal conductivity between, such that the cell has a controllable thermal conductivity between at least two locations on the cell.

[0064] According to some embodiments of the present disclosure, the method further includes calculating an electrical field intensity sufficient to induce the mixed liquid to separate to a degree yielding the desired value of the physical property for the cell.

[0065] According to some embodiments of the present disclosure, the calculating is based on at least one of: a. respective conductivities of the at least partially miscible liquids; b. respective viscosities of the at least partially miscible liquids; c. respective polarities of the at least partially miscible liquids; d. miscibility level of the at least partially miscible liquids; e. relative proportions of the at least partially miscible liquids in the mixed liquid; f. a temperature of the mixed liquid; g. the amount of charge carriers in the mixture; h. the amount of dissolved salt in the mixture; and i. the ambient temperature.

[0066] According to some embodiments of the present disclosure, the field generating element includes at least two conductive electrodes on respective sides of the conduit, connected to a power source. The electrodes may have any shape that enables it to create the transverse electric field (e.g. from wire-like to patch-like). Optionally, the field generator electrodes are covered by an insulating material (e.g. glue, tape, other plastic material, etc.).

[0067] According to some embodiments of the present disclosure, the electric field is induced in the mixed liquid by a magnetic field generator.

[0068] According to some embodiments of the present disclosure, the electric field is generated in the mixed liquid by an electric field generator.

[0069] BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order to understand the invention, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings. Features shown in the drawings are meant to be illustrative of only some embodiments of the invention, unless otherwise indicated. In the drawings like reference numerals are used to indicate corresponding parts.

[0071] In block diagrams and flowcharts, optional elements / components and optional stages may be included within dashed boxes.

[0072] In the figures:

[0073] Figs. 1-2 show the water composition and the cosolvent composition respectively across a channel as a function of increasing potential, according to an exemplary embodiment of the disclosure;

[0074] Fig. 3 shows a velocity profile across a channel for varying values of scaled potential with a polar liquid that is less viscous than the non-polar liquid, according to an exemplary embodiment of the disclosure;

[0075] Fig. 4 shows the ratio of mid-channel velocities with and without an electric potential with a polar liquid that is less viscous than the non-polar liquid, according to an exemplary embodiment of the disclosure;

[0076] Fig. 5 shows a flow amplification factor for different values of the difference between the surface energies of water and the cosolvent, according to an exemplary embodiment of the disclosure;

[0077] Fig. 6 shows a flow amplification factor for different salt contents, according to an exemplary embodiment of the disclosure; Fig. 7 shows a velocity profile across a channel for varying values of scaled potential with a polar liquid that is more viscous than the non-polar liquid, according to an exemplary embodiment of the disclosure;

[0078] Fig. 8 shows the ratio of mid-channel velocities with and without an electric potential with a polar liquid that is more viscous than the non-polar liquid, according to an exemplary embodiment of the disclosure;

[0079] Fig. 9 shows composition profiles for different channel widths at constant potential, according to an exemplary embodiment of the disclosure;

[0080] Fig. 10 shows a flow amplification ratio versus channel width, according to an exemplary embodiment of the disclosure;

[0081] Fig. 11 shows a flow amplification factor as a function of model layer thickness, according to an exemplary embodiment of the disclosure;

[0082] Figs. 12A-12B are simplified schematic illustrations of a conduit with a mixed liquid flowing therein, according to an exemplary embodiment of the disclosure;

[0083] Figs. 13A-14 are simplified block diagrams of a system for controlling liquid flow, according to respective exemplary embodiments of the presently disclosed subject matter;

[0084] Fig. 15 is a simplified flow chart of a method for controlling liquid flow, according to some embodiments of the disclosure;

[0085] Figs. 16A-16B are simplified block diagrams of a system for controlling a physical property of a cell containing a mixed liquid, according to a first exemplary embodiment of the disclosure;

[0086] Figs. 17A-17B are simplified block diagrams of a system for controlling a physical property of a cell containing a mixed liquid, according to a second exemplary embodiment of the disclosure; and

[0087] Fig. 18 is a simplified flowchart of a method for controlling a physical property of a cell, according to some embodiments of the disclosure.

[0088] DETAILED DESCRIPTION

[0089] The present disclosure, in some embodiments, thereof, relates to the properties of confined liquids, and, more particularly, but not exclusively, to the properties of confined mixtures of liquids. A model of the response of a mixed liquid flowing in a conduit to an electric field is now presented.

[0090] 1. Model

[0091] Consider a binary mixture of two liquids. The more polar liquid may be water, and the less polar one is a partially miscible cosolvent. The volume fraction, permittivity and viscosity of the water are respectively. The same quantities for the cosolvent are denoted by (Φcs, εcsand ηCs. The mixture is coupled to a reservoir containing dissolved anions and cations whose number density is no. The water and cosolvent have partial miscibility given by their coexistence (binodal) curve. It is assumed that the bulk water composition, Φ ≃ 60 and temperature correspond to a homogeneous (mixed) state. While the theory is general, in some curves, as an example for a liquid pair, for the purpose of this analysis we use the properties of water and glycerol.

[0092] The mixture is pumped into a gap between two parallel and smooth surfaces and flows parallel to the y-direction (see Fig. 12 below). The pressure gradient along the gap may result from a pump, gravitational force, etc. The length of the channel is L, and its walls are at x = +1)12. An electrostatic potential is applied across the channel in the x- direction. The resultant electric field modifies the mixture’s composition and leads to composition gradients perpendicular to the main flow direction. We assume long channels where edge effects may be ignored. The system is then effectively one-dimensional, and all quantities depend on the x-coordinate only. In addition, we focus on steady-state conditions.

[0093] We start by formulating the flow behavior based on a generic mixture free energy density / , and later choose a specific model. The governing equations for the flow velocity v, mixture composition (j), ion densities n±, and electrostatic potential ψ are:

[0094]

[0095] Equation (2.1) is the condition of incompressibility, and Eqation (2.2) is a diffusion-advection equation, with diffusion coefficient DΦ. Equation (2.4) is the Poisson equation, with ψ the electrostatic potential, e the electron’s charge, and εO and ε(Φ) the vacuum and relative permittivities respectively. Equation (2.5) is the Poisson-Nernst- Planck equation, with ion diffusion constant Di common to both ionic species. We use a modified Poisson-Boltzmann framework that takes the finite volume of the ions into account, thus: where vo is a volume common to all molecules - water, cosolvent and ions. Equation (2.3) is a Navier-Stokes equation with a force due to composition gradients, and a term feiec, derivable from the Maxwell stress tensor, given by: with the electric field The composition-dependent permittivity is taken to be: where and εcsare the water and cosolvent permittivities respectively.

[0096] The dependence of viscosity on composition is essential for electrolubrication. We assume that the ions’ contribution to the viscosity is the same as that of water, and use the following linear constitutive relation:

[0097] The assumption of an infinitely long channel means that the flow velocity is parallel to the channel axis: v = v(x)y. In steady state, all time derivatives vanish. Since there is no flux of mixture or ions from the walls, we arrive at an unexpected simplification to (2.1)-(2.5) - both the composition profile Φ(x) and ionic densities extremize the free energy: and As in equilibrium, they do not depend on DΦand Di.

[0098] Once Φ(x) and n±(x) are found, one needs to solve the Navier-Stokes equation: subject to the two boundary conditions v(x = ±Z) / 2) = 0.

[0099] 2.1. Free energy

[0100] To be specific, we use the free energy model below:

[0101] The channel walls are taken to be symmetric, hence the surface energy fsis taken as where Ay is the difference between the surface energies of water and cosolvent. The chemical potentials of the cations and anions are V± respectively, and that of the mixture is μ. The square-gradient term accounts for the energetic cost of composition inhomogeneities, where c is a constant. The free energy density of mixing is: where ki-; is the Boltzmann constant, T is the absolute temperature, and X ~ 1 / T is the Flory interaction parameter. Equation (2.11) leads to an upper critical solution temperature type phase diagram. In the plane, a homogeneous phase is stable above the binodal curve whereas below it, the mixture separates to water-rich and water-poor phases, with compositions given by The two phases become indistinguishable at the critical point

[0102] The electrostatic energy density feis given by:

[0103] The free energy density of the ions, / , is modelled as:

[0104] The logarithmic terms account for the ions’ entropy; the terms proportional to model specific chemical short-range interactions between ions and solvents. The parameters u± measure the preference of ions towards a water environment and are of order ~ 1- 10. In the following, we deal with ions that are preferentially hydrophilic, and take them as equal:

[0105] 2.2. Free energy minimization

[0106] We use the following dimensionless variables:

[0107] Here, no and Φo are the bulk ion density and mixture composition respectively, λD is the Debye length, and V is the potential drop across the channel. Using these definitions, one may extremize the energy to find the profiles Φ(x) and ψ(x) as:

[0108] The first equation expresses the variation with respect to Φ, i.e. and the second equation is Poisson’s equation. The boundary conditions for (j) and ψ are:

[0109] The ions obey a modified Boltzmann distribution:

[0110] In general, the electric double layer created at the walls leads to adsorption of the polar solvent due to the dielectrophoretic force and preferential solvation. The thickness of the resulting lubrication layer is determined by both the Debye length and the correlation length of the mixture ε, and thus may be large at temperatures close to the critical point.

[0111] 2.3. Velocity profile

[0112] Once the composition profile Φ(x) is known from (2.14), (2.15) and (2.17), v(x) may be found in the following way from Equation (2.9). We write the constant pressure drop along the channel as where Δp is the pressure drop over a channel of length L. Using the symmetry of the problem with respect to the reflection x — > -x, one arrives at the solution for the flow profile v(x) given by:

[0113] The no-flow condition at the walls, v(x = +D / 2) = 0 is satisfied. The total flux is given by the integral:

[0114] Recall that when the mixture is homogeneous with composition and viscosity ηo = η(Φo), v(x) is the classical parabolic profile:

[0115] The flux of this mixed state is:

[0116] The ‘flow amplification factor’ a is defined as the ratio between the fluxes with and without electrostatic potential: with the integrated fluxes Z and Qmtaken from Equations (2.19) and (2.21), respectively.

[0117] In the next section we solve numerically the profiles ^(x) and \| / (x), evaluate the velocity and flux from Equations (2.18) and (2.19) for the state with an electric field, and compare them with the same quantities without the field.

[0118] 2. Results

[0119] We solve Equations (2.14) and (2.15) numerically as diffusion equations with pseudo-time until the solutions do not change within the desired error. Spatial derivatives were discretized using standard schemes, and the time integration was done using the Runge-Kutta algorithm. The results were substituted in the equations to verify their validity. For example, in Equation (2.15), the right- and left-hand sides were verified to be equal within a relative error of 10-3. We used channels with scaled width D = 8XD and several values of cross-channel potential V.

[0120] Fig. 1 shows the water composition, and Fig. 2 the cosolvent composition, across the channel as a function of increasing potential. In all figures, unless stated otherwise, r / >o = 0.25, % = 1, Au = 2, sw= 80, scs= 45, c~ = 0.4, rjcs / ^w = 1412, Ay = 0 and n0= 0.001.

[0121] When V = 0, (f> equals the bulk composition r / >o = 0.25. As V increases, two boundary layers appear at the walls. The value of (f> increases near the walls, while (j>csdecreases. Their sum is not exactly unity since the dissolved ions have finite volumes. Note that V = 40 corresponds to a physical potential of 1 V. At the walls, water is enriched, therefore the viscosity there is greatly reduced locally as compared to the centre of the channel (x = 0). The inset in Fig. 2 shows the width of the water layer near the walls, w, which depends on the electrostatic screening length and on the mixture’s correlation length. The nonmonotonic behaviour of w versus V is a result of the simultaneous nonlinear decrease of screening and the stronger adsorption of water with increasing V . Fig. 3 shows the resultant velocity profiles vef(x) calculated from (2.18) for the same values of V . The curves are characterized by a thin boundary layer at the walls, where the gradient of vef(x) is large, and a large region, far from the walls, where the velocity is high and approximately constant. As V increases, the maximal speed in the centre increases, and the gradient vefnear the walls becomes even larger. Using the numerical values Δp = 1 atm, L = 0.01 m and λD = 10 nm, we estimate vefto be of the order of 1 pm s-1for the largest potential, V =40. This is almost 80 times larger than the velocity in the absence of potential.

[0122] In Fig. 4, we plot the ratio of the velocities with and without a field, Nef / Nm. Both are evaluated at their maximum, i.e. at x = 0, and vm(x) is the parabolic profile in (2.20). When 7 = 0, the two are equal. The ratio increases with V to high values - at a physical potential of just 1 V, vef(0) / vm(0) is near 80.

[0123] In the calculations thus far, the walls were neither hydrophilic nor hydrophobic, y = 0. How the flow is affected by the relative hydrophilicity of the surfaces by allowing y to vary is now addressed. Fig. 5 shows the ‘flow amplification factor’ a from (2.22). The general trend is that a(7) increases with V. Each curve corresponds to a different value of Ay. While all curves reach large flow amplification at V = 40 (a ~100), it is clear that a becomes larger monotonically as the surface hydrophilicity increases.

[0124] In Fig. 6, we look at the dependence of electrolubrication on the salt content. We calculated Qef versus V with a given amount of salt n0, and then repeated with more salt. While a increases with V and reaches high values at V = 40, it also increases monotonically as salt is added.

[0125] Until now, the polar liquid (water) was considered to be less viscous than the nonpolar one (cosolvent), thereby facilitating the two lubrication layers when potential is applied across the walls. In an opposite case the polar liquid is more viscous. If the polar liquid is very viscous, then the two layers at the walls may effectively reduce the channel width D (or pipe diameter in the case of a circular pipe).

[0126] Figs. 7-8 examine this situation. All parameter values are the same as in Figs. 1-4, except that the viscosities are interchanged: ηw / ηcs = 1412. In Fig. 7, vef is shown for varying values of V . The flow velocity is slower at any point x, in particular in the centre. Fig. 8 quantifies the reduction of the flow velocity in the center. At the maximum value, V - 40, the velocity is reduced by ~25% from its no-field case. The inset shows that:

[0127] The figures above show a dependence on V for small potentials. The small V limit may be obtained as follows: (2.14) is linearized around the bulk composition Ro using the Debye-Hiickel solution of (2.15). The homogeneous solution includes exponents with the mixture correlation length, and the particular solution includes the Debye length. Next, the Navier-Stokes equation (2.9) is solved by assuming that where vo is the parabolic profile, and δv is a small perturbation whose boundary values are The dependence of δv on is via (2.8). The perturbation 5v and the corresponding flux are proportional to V2. As a result

[0128] How does a scale with the channel width D? In Figs. 9-10, we varied D at constant pressure gradient and potential. Fig. 9 shows the profiles versus x for several values of D. Note that each curve has a different x-range. All curves exhibit a wetting layer near the walls. These layers are similar to each other because the potential is the same. The calculations assume that far from the surfaces, the composition is fixed at Ai = 0.25. Fig. 10 shows a versus D. At small channel widths, a is large since the volume fraction of the less viscous solvent (water) is high. As D increases, the volume fraction of the wetting layers becomes smaller, and a. decreases monotonically. In the limit D oo, a. tends to unity.

[0129] We now estimate a by using a simple analytical model, where two layers of pure water of thickness w are at the walls, and pure cosolvent is in the centre. Hence - 2w!D is the water volume fraction. From (2.18), one finds the velocity in the two regions to be:

[0130] From the continuity of v and the no-flow boundary conditions, it follows that

[0131] The flux integrated over the channel width is:

[0132] The flux of the mixed state may be obtained from (2.21), with the average viscosity given by r]o ( ) \ ( ) \

[0133] The ratio increases monotonically with the viscosity ratio , ηcs / ηw when w / D is held constant. One may also hold the ratio ηcs / ηwconstant and inspect a as a function of w / D. The small w / D values correspond to the large D range in Fig. 10.

[0134] Unexpectedly, as may be seen in Fig. 11, a has a maximum at a finite lubrication layer thickness w. The dashed curve shows a for the case where the less polar liquid is more viscous ( ηcs / ηw= 1412). In the solid curve, the viscosities are interchanged: the polar phase is more viscous, The existence of the maximum is due to the assumption of a closed system, where r|o depends on w, D, r]„ and qw, which is different from a system coupled to a reservoir, where

[0135] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding. However, it will be understood by those skilled in the art that the presently disclosed subject matter may be practiced without these specific details. In other instances, well-known methods and features have not been described in detail so as not to obscure the presently disclosed subject matter.

[0136] Some embodiments of the present disclosure are embodied as a system or method. For example, some embodiments of the present disclosure may take the form of an entirely hardware embodiment or an embodiment combining software and hardware aspects (including firmware, resident software, micro code, etc.) that may all generally be referred to herein as a “circuitry” and / or “system.”

[0137] Unless specifically stated otherwise, as apparent from the following discussions, it is appreciated that throughout the specification discussions utilizing terms such as "calculating", "processing", "computing", "comparing", or the like, refer to the action(s) and / or process(es) of a processor and / or computer that manipulate and / or transform data into other data, said data represented as physical, such as electronic, quantities and / or said data representing the physical objects. The term “computer” should be expansively construed to cover any kind of hardware -based electronic device with data processing capabilities.

[0138] The various illustrative logical blocks, modules, and algorithm steps described in connection with the examples disclosed herein can be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. The described functionality can be implemented in varying ways for each particular application, but such implementation decisions should not be interpreted as causing any departure from the scope of the disclosure.

[0139] It will also be understood that a system according to the present disclosure may be, at least partly, implemented on a suitably programmed computer. Likewise, the present disclosure contemplates a computer program being readable by a computer for executing the method of the present disclosure. The present disclosure further contemplates a non- transitory computer-readable memory tangibly embodying a program of instructions executable by the computer for executing the method of the present disclosure.

[0140] 3. System for controlling flow of a mixed liquid

[0141] A system for controlling liquid flow includes a conduit, a field generating element, a flow sensor and control circuitry. The flow sensor, control circuitry and field generating element are configured in a feedback arrangement. Flow rate data measured by the flow sensor is used by the control circuitry to control the field generating element, in order to obtain the desired flow rate. Some exemplary embodiments of the system are presented in more detail below.

[0142] The conduit conveys a mixed liquid which is composed of two or more at least partially miscible liquids (denoted herein the component liquids). Optionally, the component liquids have different respective polarities and different respective viscosities. The conduit may be of any size or shape suitable for the mixed liquid being conveyed. In one example the conduit is a pipe which encloses the liquid while it flows from inlet to outlet. In a second example, the conduit is a channel in which the liquid is partially exposed (e.g. open on top).

[0143] The mixed liquid flow in the conduit may be caused by many forces. Such factors include gravitational forces, other mechanical forces creating a pressure differential along the conduit (e.g. a pump), centrifugation by rotation, electroosmotic flow by an electric field parallel to the main flow direction or a magnetic field acting on embedded particles.

[0144] The field generating element generates an electric field in the mixed liquid in a direction transverse to a flow of the mixed liquid in the conduit. The intensity of the electric field generated by the field generating element controls a reversible formation of a layer of one of the component liquids along a surface of the conduit.

[0145] Optionally, the electrical field is perpendicular to the direction of flow of the mixed liquid.

[0146] As used herein, according to some embodiments of the disclosure, the term “mixed liquid” means a liquid which is a mixture of two or more liquids (also denoted “component liquids”). The component liquids are at least partially miscible with each other.

[0147] As used herein, according to some embodiments of the disclosure, the term “at least partially miscible” means that the component liquids are fully miscible or partially miscible.

[0148] As used herein, according to some embodiments of the disclosure, the term “fully miscible” means that in thermodynamic equilibrium the component liquids may mix together in any proportion to form a homogeneous solution.

[0149] As used herein, according to some embodiments of the disclosure, the term “partially miscible” means that in the absence of an electric field in thermodynamic equilibrium the component liquids may mix together in limited proportions. Beyond a certain concentration, they form separate phases resulting in the creation of layers in the mixture.

[0150] As used herein, according to some embodiments of the disclosure, the term “reversible formation of a layer” means that the layer forms when an electric field at the required intensity is present and the layer dissipates when the electric field is below the required intensity or not present.

[0151] Non-limiting examples of a field generating element include but are not limited to: a) an electric field generator, b) a magnetic field generator; c) electrodes abutting the conduit walls; or d) electrodes embedded within the conduit walls. Exemplary embodiments are described in more detail below.

[0152] The flow sensor senses the flow rate of the liquid flow in the conduit and provides flow rate data to the control circuitry. Examples of flow sensors include but are not limited to: a) an optical flow detector which senses the flow rate based on natural impurities in the liquid flowing through the conduit; b) a differential pressure flow meter; c) a Venturi flow meter; d) an ultrasonic flow meter; and e) an electromagnetic flow meter.

[0153] The control circuitry controls the field generating element so that is produces the electric field at an intensity that yields a desired flow rate of the mixed liquid. The control circuitry determines the required electric field intensity based on the flow rate data provided by the flow sensor.

[0154] The control circuitry may be of any type or configuration known in the art, and may include analog and / or digital circuitry. Optionally, the control circuitry includes one or more processors executing processing instructions. The control circuitry may include a non-volatile memory storing the processing instructions and which is accessible to the one or more processors.

[0155] Optionally, the control circuitry calculates the electrical field intensity which induces a separation of the mixed liquid to the degree that will yield the desired flow rate.

[0156] Optionally, the calculation is based on one or more of the following non-limiting list: a) respective viscosities of the at least partially miscible liquids; b) respective polarities of the at least partially miscible liquids; c) respective levels of miscibility of the at least partially miscible liquids; d) relative proportions of the at least partially miscible liquids in the mixed liquid; e) a temperature of the mixed liquid; f) the amount of dissolved salt or other charge carriers in the mixture; and g) the ambient temperature.

[0157] In some embodiments, the component liquid forming the layer along a surface of the conduit has a lower viscosity than the other liquids in the mixed liquid, such that generating the electric field increases liquid flow through the conduit.

[0158] In alternate embodiments, the component liquid forming the layer along a surface of the conduit has a higher viscosity than the other liquids in the mixed liquid, such that generating the electric field decreases liquid flow through the conduit.

[0159] In a first example, the component liquids are partially miscible, so that they separate into layers when the electric field intensity is at or exceeds a certain threshold (depending on factors such as the relative average composition of the mixed liquid, the temperature of the mixed liquid, etc.). A layer of one of the component liquids forms along the conduit wall. If the threshold has not been crossed, the flow rate varies smoothly with field intensity. The flow rate exhibits step-transition between flow rates once the threshold field intensity is crossed.

[0160] In a second example, the component liquids are fully miscible. The component layers do not necessarily separate into separate layers when the electric field intensity is at a certain level. Instead, the electric field causes the mixture of component liquids to become non-homogeneous. A component liquid is attracted to the conduit wall and forms a layer along it, and the concentration of the remaining component liquid(s) increases in the center of the conduit. In this case the flow rate may change gradually in accordance with changes in the intensity of the electric field.

[0161] Reference is now made to Figs. 12A-12B, which are simplified schematic illustrations of a conduit with a mixed liquid flowing therein, according to an exemplary embodiment of the disclosure. Figs. 12A-12B show a simplified example of the separation of the mixed liquid under the influence of an electric field and its effect on liquid flow, as presented above.

[0162] In Figs. 12A-12B, two flat and smooth walls form a conduit which is parallel to y-z plane. The walls are separated by a distance D in the x-direction. The confined liquid mixture flows along y. In steady state, the velocity depends on x: v = v(x)y". In Fig. 12A, the liquid mixture is homogeneous, its viscosity is r|(cpO) and the flow is the classic parabolic profile. In Fig. 12B a potential is applied across the walls, the mixture phase separates and two regions 1210 rich in the more polar solvent appear near the walls. When the more polar component liquid is the less viscous one lubrication layers are formed, which modify the flow profile. The strong shear near the surfaces facilitates a large flux.

[0163] In a first example, the mixed liquid is a mixture of water and at least one petroleum product.

[0164] In a second example, the mixed liquid is a mixture of water and glycerol.

[0165] In a third example, the mixed liquid is a mixture of water and alcohol.

[0166] In a fourth example, the mixed liquid is a mixture of two or more polar liquids; and

[0167] In a fifth example, the mixed liquid is a mixture of at least one polar liquid and one or more nonpolar liquids;

[0168] In a sixth example, the mixed liquid is a polymer solution.

[0169] Reference is now made to Figs. 13A-14, which are simplified block diagrams of a system for controlling liquid flow, according to respective exemplary embodiments of the presently disclosed subject matter.

[0170] The mixed liquid flows through conduit 1310. Flow sensor 1320 measures the flow of the mixed liquid through conduit 1310 and provides the flow rate data to control circuitry 1330. Control circuitry 1330 controls field generating element (1340, 1350.1 / 1350.2, 1360 and 1370 respectively), so that the intensity of the electrical field it generates in the mixed liquid is at a level which yields the desired flow rate.

[0171] As can be seen, the connection between flow sensor 1320, control circuitry 1330 and the field generating element forms a feedback loop, so that control circuitry 1330 may continuously or periodically adjust the field generating element based on the flow rate data collected by flow sensor 1320.

[0172] Fig. 13A is an exemplary embodiment of a system 1301 for controlling liquid flow in which the field generating element 1340 is an electric field generator.

[0173] Fig. 13B is an exemplary embodiment of a system 1302 for controlling liquid flow in which the field generating element includes electrodes 1350.1 and 1350.2 on respective sides of the conduit. In a first example, the electrodes are exterior to conduit 1310 and are mounted on it. In a second example, the electrodes are embedded in conduit 1310.

[0174] Fig. 13C is an exemplary embodiment of a system 1303 for controlling liquid flow in which the field generating element 1350 is a magnetic field generator. The magnetic field generated by magnetic field generator 1350 induces an electric field in the mixed liquid in a direction transverse to the liquid flow direction. For example, considering the x-axis to be the direction of fluid flow and the y-axis to be a distance between the conduit walls, a magnetic field generated along the z-axis will cause a force acting on moving charge carriers that will lead to charge separation and a transverse electric field in the mixed liquid.

[0175] Inducing the electric field using a magnetic field generator may be particularly suitable for relatively large conduits because the magnetic field is not screened. Therefore the charge separation and resulting electric field may occur relatively far from the conduit walls even when the fields are static. The effect of the magnetic field, being relatively weak, is enhanced when the conduits are large.

[0176] Fig. 14 is an exemplary embodiment of a system 1400 for controlling liquid flow which includes additional optional components, one or more of which may be included in an embodiment of the system. Field generating element 1370 may be of any kind capable of generating a transverse electrical field in the mixed fluid, including by not limited to the examples of Figs. 13A-13C.

[0177] Optionally, system 1400 further includes pump 1380 which creates a pressure differential along the conduit, causing the mixed liquid to flow through the conduit.

[0178] Optionally, system 1400 further includes container 1390 which contains the mixed liquid and provides the mixed liquid to the conduit inlet. Optionally, system 1400 further includes temperature control element 1391 which maintains the mixed liquid at a temperature at which the layer forms along the surface of the conduit when the electric field is generated across the conduit.

[0179] In some embodiments according to the disclosure, the conduit is a pipe. In one example the pipe is made of a flexible material (e.g. silicone). In a second example, the pipe is made of a rigid material.

[0180] In some embodiments according to the disclosure, the conduit is a channel. In one example the channel is made of a flexible material (e.g. silicone). In a second example, the channel is made of a rigid material.

[0181] In some embodiments according to the disclosure, the conduit is a supply line in an inkjet print cartridge.

[0182] In some embodiments according to the disclosure, the conduit is a supply line in a paint spray device.

[0183] In some embodiments according to the disclosure, the conduit is configured to convey a mixture which includes at least one petroleum product and at least one polar liquid.

[0184] In some embodiments according to the disclosure, the conduit is a component of a microfluidic device.

[0185] 4. Method of controlling flow of a mixed liquid

[0186] Reference is now made to Fig. 15, which is a simplified flow chart of a method for controlling liquid flow, according to some embodiments of the disclosure. The mixed liquid includes two or more at least partially-miscible liquids, as described above.

[0187] In 1510 an electric field is generated in the mixed liquid in a direction transverse to the flow of the mixed liquid through the conduit. The intensity of the electric field is sufficient to induce the mixed liquid to separate at least partially, so that one of the at least partially miscible component liquids forms a layer along a surface of the conduit.

[0188] In 1520, the intensity of the electric field is controlled to yield a desired flow rate of the mixed liquid, based on flow rate data provided by a flow sensor.

[0189] Optionally, the intensity of the electric field yielding the desired flow rate of the liquid is calculated based on at least one of: a) respective viscosities of the at least partially miscible liquids; b) respective polarities of the at least partially miscible liquids; c) respective levels of miscibility of the at least partially miscible liquids; d) relative proportions of the at least partially miscible liquids in the mixed liquid; e) a temperature of the mixed liquid; f) the amount of dissolved salt or other charge carriers in the mixture; and g) the ambient temperature.

[0190] In a first optional embodiment, the electric field is generated by at least two electrodes on respective sides of the conduit.

[0191] In a second optional embodiment, the electric field is generated by an electric field generator.

[0192] In a third optional embodiment, the electric field is generated by a magnetic field generator that induces the electric field in the mixed liquid.

[0193] Optionally, the electrical field is perpendicular to the direction of flow of the mixed liquid.

[0194] Optionally, the partially miscible liquids have different respective polarities and different respective viscosities.

[0195] Optionally, the component liquid forming the layer along the surface of the conduit has a lower viscosity than the other component liquids in the mixed liquid, such that generating the electric field increases liquid flow through the conduit. Alternately, the component liquid forming the layer along the surface has a higher viscosity than the other component liquids in the mixed liquid, such that generating the electric field decreases liquid flow through the conduit.

[0196] Optionally the method further includes maintaining the mixed liquid at a temperature at which the layer forms along the surface of the conduit when the electric field is generated across the conduit.

[0197] Optionally the method further includes comprising creating a pressure differential along the conduit, so as to cause the mixed liquid to flow through the conduit.

[0198] In some embodiments according to the disclosure, the conduit is a pipe. In one example the pipe is made of a flexible material (e.g. silicone). In a second example, the pipe is made of a rigid material. In some embodiments according to the disclosure, the conduit is a channel. In one example the channel is made of a flexible material (e.g. silicone). In a second example, the channel is made of a rigid material.

[0199] Optionally, the conduit is a nozzle.

[0200] Optionally, the conduit is a supply line an inkjet print cartridge or paint spray device.

[0201] Optionally, the conduit is configured to convey a mixture comprising at least one petroleum product and at least one polar liquid.

[0202] Optionally, the conduit is a component of a microfluidic device.

[0203] Optionally, the mixed liquid is one of: a) a mixture of water and at least one petroleum product; b) a mixture of water and glycerol; c) a mixture of water and alcohol; d) a mixture of a plurality of polar liquids; e) a mixture of at least one polar liquid and one or more nonpolar liquids; f) a polymer solution.

[0204] 5. System for controlling a physical property of a cell

[0205] According to some embodiments of the disclosure, a system for controlling a physical property of a cell containing a mixed liquid includes a field generating element and control circuitry.

[0206] The field generating element generates an electric field in a cell containing a mixed liquid.

[0207] The cell fully or partially encloses a mixed liquid composed of multiple at least partially miscible liquids. The cell may be of any size or shape suitable for the implementation of interest. For example, the cell may be a closed capsule or tube, which is completely or partially filled with the mixed liquid. In other examples, cell may be partially open, such as an open container or pool filled with the mixed liquid.

[0208] The mixed liquid contains two or more component liquids, which are partially or fully miscible. At least two of the component liquids have different respective values of a physical property, whose value may be controlled by applying an electric field to the cell. The electric field controls a reversible transition of the composition of component liquids in the mixed liquid from a uniform composition to a non-uniform composition. The value of the physical property for the cell is different for the uniform and non- uniform compositions.

[0209] Optionally, the electric field causes the mixed liquid to form a layer of a component liquid near and parallel to an inner surface of the cell.

[0210] As used herein, according to some embodiments of the disclosure, the term “uniform composition” means that the component liquids have the same relative proportions in all the cell.

[0211] As used herein, according to some embodiments of the disclosure, the term “non- uniform composition” means that the component liquids have the different relative proportions in different parts of the cell.

[0212] As used herein, according to some embodiments of the disclosure, the term “reversible transition of a composition of the at least partially miscible component liquids in the mixed liquid from a uniform composition to a non-uniform composition” and similar terms mean that the mixed liquid is capable of changing from a uniform composition to a non-uniform composition and from a non-uniform composition to a uniform composition, based on the intensity of the electric field applied to the cell.

[0213] In some embodiments of the disclosure the physical property is the electrical conductivity between at least two locations on the cell, so that the cell has a controllable electrical conductivity between the locations.

[0214] In some embodiments of the disclosure the physical property is the permittivity between at least two locations on the cell, so that the cell has a controllable permittivity and capacitance between the locations.

[0215] Optionally, electrical conductors (e.g. metal wires) are connected to the locations on the cell and connect the cell to other components of the electrical circuit or device it is a part of.

[0216] In some embodiments of the disclosure the physical property is the thermal conductivity between at least two locations on the cell, so that the cell has a controllable thermal conductivity between the locations. In some embodiments of the disclosure the electrical field may control more than one physical property of the cell, and the physical properties being controlled using an electrical field are electrical conductivity and / or permittivity and / or thermal conductivity.

[0217] Consider an example in which the physical property being controlled is electrical conductivity, the mixed liquid contains two component liquids and has a certain electrical conductivity when the mixed liquid has a uniform composition. When an electrical field is applied and the composition becomes non-uniform, electrical charge will pass between the locations through the component liquid having a higher conductivity. Thus the overall conductivity of the cell between two suitable locations will increase. The conductivity of the cell will decrease for two other suitable locations.

[0218] Similar effects occur for permittivity and thermal conductivity.

[0219] The differences in the respective values of the physical property of the component liquids should be large enough so that changes in the uniformity of the mixed liquid cause substantial changes in the value of the physical property of the entire cell.

[0220] Optionally, the material the cell is formed of is electrically non-conductive, such as plastic (transparent or opaque).

[0221] As used herein, according to some embodiments of the disclosure, the term “locations on the cell” means a portion on the surface of the cell. The size of the portion of the surface is not limited to a specific size and may be as large or small as required. For example, if the physical property being controlled is conductivity, each location may be a connection to an electrode. In another example, the physical property being controlled is thermal conductivity and the locations may be larger in order to enable heat transfer between elements thermally coupled to each location.

[0222] The control circuitry controls the field generating element so that it produces the electric field in the cell at an intensity yielding the desired composition of the component liquids in the mixed liquid, resulting in the desired value of the physical property.

[0223] Optionally, the calculation is based on at least one of: a) respective conductivities of the at least partially miscible liquids; b) respective viscosities of the at least partially miscible liquids; c) respective polarities of the at least partially miscible liquids; d) miscibility level of the at least partially miscible liquids; e) relative proportions of the at least partially miscible liquids in the mixed liquid; f) a temperature of the mixed liquid; g) the amount of dissolved salt or other charge carriers in the mixture; and h) the ambient temperature.

[0224] Optionally, one or more of the component liquids is non-polar.

[0225] Optionally, the field generating element is one of the embodiments described above.

[0226] In one example, the field generating element includes at least two electrodes on respective sides of the cell.

[0227] In a second example, the field generating element is a magnetic field generator which generates a magnetic field that induces the electric field in the mixed liquid.

[0228] In a third example, the field generating element is an electric field generator.

[0229] Optionally, the system is configured for modifying a lubrication layer of a microfluidic device.

[0230] Figs. 16A-17B are now described. For clarity, Figs. 16A-17B show non-limiting examples in which the cross-section of the cell is rectangular. As noted above, the cell shape may differ for different implementations, and the cell cross-section may be non- rectangular.

[0231] Reference is now made to Figs. 16A-16B, which are simplified block diagrams of a system for controlling a physical property of a cell containing a mixed liquid, according to a first exemplary embodiment of the disclosure.

[0232] Cell 1610 encloses a mixed liquid having component liquids with controllable electrical conductivity and / or permittivity. Field generating element 1620 generates an electric field in the liquid within cell 1610. The electric field causes changes to the uniformity of the mixed liquid composition.

[0233] In Fig. 16A, field generating element 1620 is not generating an electric field and the composition is uniform. In Fig. 16B, field generating element 1620 is generating an electric field with an intensity sufficient to cause a non-uniform composition of the mixed liquid, thereby changing the value of the electrical conductivity and / or permittivity from the value(s) of the uniform composition. Control circuitry 1630 controls field generating element 1620 so that it produces an electric field at an intensity that yields the desired composition of the component liquids in the mixed liquid, and thus the desired value of the electrical conductivity and / or permittivity.

[0234] Electrical conductors A and B (e.g. metal wires) connect to respective locations on the surface of cell 1610. The electrical conductors connect cell 1610 electrically to other components of the electric circuit it is a component of.

[0235] Reference is now made to Figs. 17A-17B, which are simplified block diagrams of a system for controlling a physical property of a cell containing a mixed liquid, according to a second exemplary embodiment of the disclosure. In Figs. 17A-17B, the system controls the thermal conductivity of the cell.

[0236] Cell 1710 encloses a mixed liquid having component liquids with different respective thermal conductivities. Field generating element 1720 generates an electric field in the liquid within cell 1710. The electric field causes changes to the uniformity of the mixed liquid composition.

[0237] In Fig. 17A, field generating element 1720 is not generating an electric field and the composition is uniform. In Fig. 17B, field generating element 1720 is generating an electric field with an intensity sufficient to cause a non-uniform composition of the mixed liquid, thereby changing the value of the electrical thermal conductivity from the value of the uniform composition.

[0238] Control circuitry 1730 controls field generating element 1720 so that it produces an electric field at an intensity that yields the desired composition of the component liquids in the mixed liquid, and thus the desired value of the thermal conductivity between elements. In one example the thermal conductivity is controlled between C and D. In other examples the thermal conductivity is controlled between C and E, between D and E, between E and F, and so forth.

[0239] 6. Method for controlling a physical property of a cell

[0240] Reference is now made to Fig. 18, which is a simplified flowchart of a method for controlling a physical property of a cell, according to some embodiments of the disclosure. In 1810 an electric field is generated in a cell containing a mixed liquid containing multiple component liquids. The component liquids are at least partially miscible liquids. At least two of the component liquids have different respective values of at least one physical property.

[0241] The intensity of the electric field controls a reversible transition of the composition of the component liquids in the mixed liquid from a uniform composition to a non-uniform composition. The value of the physical property of the cell is different for the uniform and non-uniform compositions.

[0242] In 1820, the intensity of the electric field is controlled to obtain the desired composition of the component liquids in the mixed liquid, thus obtaining the desired value of the physical property.

[0243] In some embodiments of the disclosure the physical property is the electrical conductivity between two locations on the cell, so that the cell has a controllable electrical conductivity between the locations.

[0244] In some embodiments of the disclosure the physical property is the permittivity between two locations on the cell, so that the cell has a controllable permittivity between the locations.

[0245] In some embodiments of the disclosure the physical property is the thermal conductivity between two locations on the cell, so that the cell has a controllable thermal conductivity between the locations.

[0246] In some embodiments of the disclosure the electrical field may control more than one physical property of the cell, and the physical properties being controlled using an electrical field are electrical conductivity and / or permittivity and / or thermal conductivity.

[0247] Optionally, in 1840 the electrical field intensity sufficient to induce the mixed liquid to separate to a degree yielding the desired value of the physical property for the cell is calculated. A field generating element may be controlled to generate an electric field in the cell at the calculated intensity level.

[0248] Optionally, the calculation is based on at least one of: a) respective conductivities of the at least partially miscible liquids; b) respective viscosities of the at least partially miscible liquids; c) respective polarities of the at least partially miscible liquids; d) miscibility level of the at least partially miscible liquids; e) relative proportions of the at least partially miscible liquids in the mixed liquid; f) a temperature of the mixed liquid; g) the amount of dissolved salt or other charge carriers in the mixture; and h) the ambient temperature.

[0249] Optionally, one of the component liquids is non-polar.

[0250] Optionally, the field generating element is of any of the embodiments described above.

[0251] In one example, the field generating element includes at least two electrodes on respective sides of the cell.

[0252] In a second example, the field generating element is a magnetic field generator which generates a magnetic field that induces the electric field in the mixed liquid.

[0253] In a third example, the field generating element is an electric field generator.

[0254] Optionally, the method is used to modify a lubrication layer of a microfluidic device.

[0255] Those skilled in the art to which the present disclosure pertains, can appreciate that while the present disclosure has been described in terms of preferred examples, the concept upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, systems and processes for carrying out the several purposes of the present disclosure.

[0256] The terms “comprises”, “comprising”, “includes”, “including”, “having” and their conjugates mean “including but not limited to”.

[0257] The term “consisting of’ means “including and limited to”.

[0258] As used herein, singular forms, for example, “a”, “an” and “the” include plural references unless the context clearly dictates otherwise.

[0259] Within this application, various quantifications and / or expressions may include use of ranges. Range format should not be construed as an inflexible limitation on the scope of the present disclosure. Accordingly, descriptions including ranges should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within the stated range and / or subrange, for example, 1, 2, 3, 4, 5, and 6. Whenever a numerical range is indicated within this document, it is meant to include any cited numeral (fractional or integral) within the indicated range.

[0260] It is appreciated that certain features which are (e.g., for clarity) described in the context of separate embodiments, may also be provided in combination in a single embodiment. Where various features of the present disclosure, which are (e.g., for brevity) described in a context of a single embodiment, may also be provided separately or in any suitable sub-combination or may be suitable for use with any other described embodiment. For example, methods, sensors, illumination, processing circuitry described with some embodiments may be used with other embodiments as well. Features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

[0261] Although the present disclosure has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, this application intends to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

[0262] It is important, therefore, that the scope of the present disclosure is not construed as being limited by the illustrative examples set forth herein. Other variations are possible within the scope of the present disclosure as defined in the appended claims. Other combinations and sub-combinations of features, functions, elements and / or properties may be claimed through amendment of the present claims or presentation of new claims in this or a related application. Such amended or new claims, whether they are directed to different combinations or directed to the same combinations, whether different, broader, narrower or equal in scope to the original claims, are also regarded as included within the subject matter of the present description.

[0263] All references (e.g., publications, patents, patent applications) mentioned in this specification are herein incorporated in their entirety by reference into the specification, e.g., as if each individual publication, patent, or patent application was individually indicated to be incorporated herein by reference. Citation or identification of any reference in this application should not be construed as an admission that such reference is available as prior art to the present disclosure. In addition, any priority document(s) and / or document(s) related to this application (e.g., co-filed) are hereby incorporated herein by reference in its / their entirety.

[0264] Where section headings are used in this document, they should not be interpreted as necessarily limiting.

Claims

CLAIMS:

1. A system for controlling liquid flow, comprising: a conduit configured for conveying a mixed liquid comprising a plurality of at least partially miscible liquids; a field generating element, configured for generating an electric field in said mixed liquid in a direction transverse to a flow of said mixed liquid in the conduit, wherein an intensity of said electric field controls a reversible formation of a layer of one of the plurality of at least partially miscible liquids along a surface of the conduit; a flow sensor associated with said conduit, configured for sensing a flow rate of said liquid flow in said conduit; and a control circuitry associated with said field generating element and said flow sensor, configured for controlling said field generating element to produce said electric field at an intensity yielding a desired flow rate of said mixed liquid based on flow rate data provided by said flow sensor.

2. The system of claim 1 , wherein said control circuitry is further configured to calculate an electrical field intensity sufficient to induce a separation of said mixed liquid to a degree yielding said desired flow rate.

3. The system of claim 2, wherein said calculating is based on at least one of: respective viscosities of said at least partially miscible liquids; respective polarities of said at least partially miscible liquids; respective levels of miscibility of said at least partially miscible liquids; relative proportions of said at least partially miscible liquids in said mixed liquid; a temperature of said mixed liquid, the amount of charge carriers in the mixture; the amount of dissolved salt in the mixture; and the ambient temperature.

4. The system of any one of claims 1-3, wherein said field generating element comprises at least two electrodes on respective sides of said conduit.

5. The system of any one of claims 1-3, wherein said field generating element comprises an electric field generator.

6. The system of any one of claims 1-3, wherein said field generating element comprises a magnetic field generator configured to generate a magnetic field that induces said electric field in said mixed liquid in said direction transverse to said liquid flow direction.

7. The system of any one of claims 1-6, wherein the electrical field is perpendicular to the direction of flow of said mixed liquid.

8. The system of any one of claims 1-7, wherein the plurality of at least partially miscible liquids have different respective polarities and different respective viscosities.

9. The system of any one of claims 1-8, wherein said liquid forming said layer along said surface has a lower viscosity than the other liquids in said mixed liquid, such that generating said electric field increases liquid flow through said conduit.

10. The system of any one of claims 1-8, wherein said liquid forming said layer along said surface has a higher viscosity than the other liquids in said mixed liquid, such that generating said electric field decreases liquid flow through said conduit.

11. The system of any one of claims 1-10, further comprising a temperature control element configured to maintain the mixed liquid at a temperature at which said layer forms along said surface of the conduit when said electric field is generated across the conduit.

12. The system of any one of claims 1-11, further comprising a pump configured to create a pressure differential along said conduit, so as to cause said mixed liquid to flow through the conduit.

13. The system of any one of claims 1-12, further comprising a container configured for containing the mixed liquid and providing the mixed liquid to a conduit inlet.

14. The system of any one of claims 1-13, wherein the conduit comprises a pipe.

15. The system of any one of claims 1-13, wherein the conduit comprises a channel.

16. The system of any one of claims 1-13, wherein said conduit comprises a supply line in one of an inkjet print cartridge or paint spray device.

17. The system of any one of claims 1-13, wherein said conduit is configured to convey a mixture comprising at least one petroleum product and at least one polar liquid.

18. The system of any one of claims 1-13, wherein said conduit is a component of a microfluidic device and is configured to transport mixed liquids.

19. The system of any of claims 1-18, wherein said mixed liquid comprises one of: a mixture of water and at least one petroleum product; a mixture of water and glycerol; a mixture of water and alcohol; a plurality of polar liquids; a mixture of at least one polar liquid and at least one nonpolar liquid; and a polymer solution.

20. The system of any one of claims 1-19, wherein said flow sensor comprises one of: an optical flow detector; a differential pressure flow meter; a Venturi flow meter; an ultrasonic flow meter; and an electromagnetic flow meter.

21. A method for controlling liquid flow, comprising: generating an electric field in a mixed liquid comprising a plurality of at least partially miscible liquids in a direction transverse to a flow of said mixed liquid through a conduit and at an intensity sufficient to induce the mixed liquid to separate at least partially, so that one of the plurality of at least partially miscible liquids forms a layer along a surface of the conduit; and controlling an intensity of said electric field to yield a desired flow rate of said mixed liquid, based on flow rate data provided by a flow sensor.

22. The method of claim 21, wherein said intensity of said electric field yielding said desired flow rate of said liquid is calculated based on at least one of: respective viscosities of said at least partially miscible liquids; respective polarities of said at least partially miscible liquids; respective levels of miscibility of said at least partially miscible liquids; relative proportions of said at least partially miscible liquids in said mixed liquid; a temperature of said mixed liquid, the amount of charge carriers in the mixture; the amount of dissolved salt in the mixture; and the ambient temperature.

23. The method of claim 21 or claim 22, wherein said electric field is generated by at least two electrodes on respective sides of said conduit.

24. The method of claim 21 or claim 22, wherein said electric field is generated by an electric field generator.

25. The method of claim 21 or claim 22, wherein said electric field is generated by a magnetic field generator configured to generate a magnetic field that induces said electric field in said mixed liquid in said direction transverse to said liquid flow direction.

26. The method of any one of claims 21-25, wherein the electrical field is perpendicular to the direction of flow of said mixed liquid.

27. The method of any one of claims 21-26, wherein the plurality of at least partially miscible liquids have different respective polarities and different respective viscosities.

28. The method of any one of claims 21-27, wherein said liquid forming said layer along said surface has a lower viscosity than the other liquids in said mixed liquid, such that generating said electric field increases liquid flow through said conduit.

29. The method of any one of claims 21-27, wherein said liquid forming said layer along said surface has a higher viscosity than the other liquids in said mixed liquid, such that generating said electric field decreases liquid flow through said conduit.

30. The method of any one of claims 21-29, further comprising maintaining the mixed liquid at a temperature at which said layer forms along said surface of the conduit when said electric field is generated across the conduit.

31. The method of any one of claims 21-30, further comprising creating a pressure differential along said conduit, so as to cause said mixed liquid to flow through the conduit.

32. The method of any one of claims 21-31, wherein the conduit comprises a pipe.

33. The method of any one of claims 21-31, wherein the conduit comprises a channel.

34. The method of any one of claims 21-31, wherein said conduit comprises a supply line in one of an inkjet print cartridge or paint spray device.

35. The method of any one of claims 21-31, wherein said conduit is configured to convey a mixture comprising at least one petroleum product and at least one polar liquid.

36. The method of any one of claims 21-31, wherein said conduit is a component of a microfluidic device.

37. The method of any of claims 21-36, wherein said mixed liquid comprises one of: a mixture of water and at least one petroleum product; a mixture of water and glycerol; a mixture of water and alcohol; a plurality of polar liquids; a mixture of at least one polar liquid and at least one nonpolar liquid; and a polymer solution.

38. A system for controlling a physical property of a cell containing a mixed liquid, comprising: a field generating element, configured for generating an electric field in a cell containing a mixed liquid, said mixed liquid comprising a plurality of at least partially miscible liquids, at least two of said plurality of at least partially miscible liquids having different respective values of a same physical property, wherein an intensity of said electric field controls a reversible transition of a composition of said plurality of at least partially miscible liquids in said mixed liquid from a uniform composition to a non-uniform composition, and wherein a value of said physical property for said cell is different for said uniform and non-uniform compositions; and a control circuitry associated with said field generating element, configured for controlling said field generating element to produce said electric field at an intensity yielding a desired composition of said plurality of at least partially miscible liquids in said mixed liquid, wherein said physical property comprises one of: an electrical conductivity between two locations on said cell, a permittivity between two locations on said cell, or a thermal conductivity between two locations on said cell.

39. The system of claim 38, wherein said electric field causes at least partial separation of said at least partially miscible liquids within said cell, said control circuitry being configured to calculate an electrical field intensity sufficient to induce the mixed liquid to separate to a degree yielding a desired value of the physical property.

40. The system of claim 39, wherein said calculating is based on at least one of: respective conductivities of said at least partially miscible liquids; respective viscosities of said at least partially miscible liquids; respective polarities of said at least partially miscible liquids; miscibility level of said at least partially miscible liquids; relative proportions of said at least partially miscible liquids in said mixed liquid; a temperature of said mixed liquid, the amount of charge carriers in the mixture; the amount of dissolved salt in the mixture; and the ambient temperature.

41. The system of any one of claims 38-40, wherein said physical property comprises electrical conductivity, such that said cell has a controllable electrical conductivity between said locations.

42. The system of any one of claims 38-40, wherein said physical property comprises permittivity, such that said cell has a controllable permittivity between said locations.

43. The system of any one of claims 38-40, wherein said physical property is thermal conductivity, such that said cell has a controllable thermal conductivity between said locations.

44. The system of any one of claims 38-43, wherein said field generating element comprises at least two electrodes on respective sides of said cell.

45. The system of any one of claims 38-43, wherein said field generating element comprises a magnetic field generator configured to generate a magnetic field that induces said electric field in said mixed liquid.

46. The system of any one of claims 38-43, wherein said field generating element comprises an electric field generator.

47. The system of any one of claims 38-45, configured for modifying a lubrication layer of a microfluidic device.

48. A method for controlling a physical property of a cell, comprising: generating an electric field in a cell containing a mixed liquid, said mixed liquid comprising a plurality of at least partially miscible liquids, at least two of said plurality of at least partially miscible liquids having different respective values of a same physical property, wherein an intensity of said electric field controls a reversible transition of a composition of said plurality of at least partially miscible liquids in said mixed liquid from a uniform composition to a non-uniform composition, and wherein a value of said physical property for said cell is different for said uniform and non-uniform compositions; andcontrolling said intensity of said electric field so as to obtain a desired composition of said plurality of at least partially miscible liquids in said mixed liquid, wherein said physical property comprises one of: an electrical conductivity between two locations on said cell, a permittivity between two locations on said cell, or a thermal conductivity between two locations on said cell.

49. The method of claim 48, wherein said physical property is electrical conductivity, such that said cell has a controllable electrical conductivity between at least two electrodes electrically connected to respective locations on said cell.

50. The method of claim 48 or claim 49, wherein said physical property comprises permittivity, such that said cell has a controllable electrical conductivity between said locations.

51. The method of any one of claims 48-50, wherein said conductivity is thermal conductivity between, such that said cell has a controllable thermal conductivity between at least two locations on said cell.

52. The method of any one of claims 48-51, further comprising calculating an electrical field intensity sufficient to induce the mixed liquid to separate to a degree yielding the desired value of said physical property for said cell.

53. The method of claim 52, wherein said calculating is based on at least one of: respective conductivities of said at least partially miscible liquids; respective viscosities of said at least partially miscible liquids; respective polarities of said at least partially miscible liquids; miscibility level of said at least partially miscible liquids; relative proportions of said at least partially miscible liquids in said mixed liquid; a temperature of said mixed liquid; the amount of charge carriers in the mixture;the amount of dissolved salt in the mixture; and the ambient temperature.

54. The method of any one of claims 48-53, wherein said electric field is generated in said mixed liquid by at least two electrodes on respective sides of said cell.

55. The method of any one of claims 48-53, wherein said electric field is induced in said mixed liquid by a magnetic field generator.

56. The method of any one of claims 48-53, wherein said electric field is generated in said mixed liquid by an electric field generator.

Images