a to the second end 10b. The flow meter 1 can have any suitable length L. In some embodiments, the length L of the flow meter 1 can be in a range from, for example, 2 mm to 5 mm, in a range from, for example, 2 mm to 4 mm, in a range from, for example, 3 mm to 5 mm, and in a range from, for example, 3 mm to 4 mm.

The elements 12a-12e of the flow meter 1 illustrated in FIG. 1 can be equally spaced along the flow path 14 (or the length L) of the flow meter 1. However, in some embodiments, spaces between the elements 12a-12e can vary. In some embodiments, a gap or spacing between one of the elements 12a-12e and an adjacent element 12a-12e can be about 1 mm. In some embodiments, the gap can be in a range from, for example, 0.5 mm to 2 mm, in a range from, for example, 0.5 m to 1.5 mm, in a range from, for example, 0.5 m to 1 mm, in a range from, for example, 1 m to 2 mm, or in a range from, for example, 1 m to 1.5 mm. In some embodiments, each of the heating/sensing elements 12a-12e can have a resistance in a range from, for example, 100Ω to 1000Ω, in a range from, for example, 100Ω to 500Ω, in a range from, for example, 300Ω to 1000Ω, in a range from, for example, 500Ω to 1000Ω, in a range from, for example, 300Ω to 500Ω.

FIG. 2 is a schematic cross sectional side view taken along the element 12d of the flow meter 1 illustrated in FIG. 1. Cross sectional side views taken along other elements 12a, 12b, 12c, 12e can be the same as or generally similar to what is illustrated in FIG. 2. The flow meter 1 can have a round arched overall shape in the cross sectional side view as seen in FIG. 2, with a curved flow path 14 through at or near the center of the flow meter 1, and an omega shaped conductive material 12 at least partially around the flow path 14. For example, as explained above, the elements 12a-12e can have a rounded or curved portion 15 that extends around the flow path 14 and opposing feet 17, 19 that extend radially outward from the curved portion 15. In various embodiments, the curved portion 15 of the elements 12a-12e can extend around the flow path 14 by an angle greater than 180°, or greater than 270°. However, in other embodiments, the flow meter 1 can comprise any other suitable shapes and geometries.

As illustrated in FIG. 2, at least a portion of the elements 12a-12e can be exposed to the flow path 14 so as to contact the fluid substance that flows through the flow path 14, in some embodiments. It can be beneficial to have the elements 12a-12e contact the fluid substance in some embodiments as it can be operated with less power as compared to embodiments where the elements 12a-12e are not in contact with the fluid substance. However, in some other embodiments, the elements 12a-12e may be exposed to the flow path 14 without directly contacting the fluid substance. For example, a portion of the housing 10 can be disposed between the elements 12a-12e and the flow path 14. In some embodiments, the elements 12a-12e can be exposed to the flow path 14 by way of an intervening material or coating, such that the elements 12a-12e may not directly contact the fluid substance. Rather, the material or coating may physically intervene between the fluid substance and the elements 12a-12e, but the intervening material or coating may be sufficiently thermally conductive so as to effectively transfer heat between the elements 12a-12e and the fluid substance.

Each of the elements 12a-12e can comprise the feet 17, 19 that can include a first terminal 16 and a second terminal 18 respectively. In some embodiments, the first terminal 16 can comprise an input terminal and the second terminal 18 can comprise an output terminal. In some embodiment, the first terminal 16 can comprise an anode terminal and the second terminal 18 can comprise a cathode terminal. In some embodiments, the first terminal 16 and the second terminal 18 can be coupled to additional components (not illustrated) or an external component by way of conductive connectors, such as wires, ribbon interconnects and the like. In some embodiments, the first terminal 16 and the second terminal 18 can be configured to attach to the additional components or the external device by way of solder bumps. The additional components or the external device can comprise a controller 9 (see FIG. 7) configured to, for example, analyze data obtained through the sensing elements. In some embodiments, the first terminal 16 and the second terminal 18 can extend to define a dual in-line package (DIP) structure that can be mounted to a printed circuit board (PCB).

The flow path 14 of the flow meter 1 has a diameter D. The flow meter 1 can have any suitable diameter D. In some embodiments, the diameter D can be in a range from, for example, 0.5 mm to 1 mm, in a range from, for example, 0.5 mm to 0.8 mm, in a range from, for example, 0.5 mm to 0.7 mm, in a range from, for example, 0.7 mm to 1 mm, or in a range from, for example, 0.8 mm to 1 mm. For example, when the diameter D is 0.5 mm, a volume of the flow path between a heating element and a sensing element that is spaced apart by 1 mm can be about 0.196 mm³(or microliter). As such, a volume of the flow path between five elements that are spaced apart by 1 mm can be about 1 mm³(or microliter). For another example, when the diameter D is 0.5 mm, a volume of the flow path between a heating element and a sensing element that is spaced apart by 0.5 mm can be about 0.1 mm3 (or microliter). For another example, when the diameter D is 1 mm, a volume of the flow path between a heating element and a sensing element that is spaced apart by 5 mm can be about 4 mm³(or microliter). As such, a volume of the flow path 14 in the flow meter 1 can vary based at least in part on the diameter D and the length L of the flow meter 1. The volume of the flow path 14 in the flow meter 1 can be in a range of, for example, 0.1 mm³(or microliter) to 16 mm³(or microliter), in a range of, for example, 0.5 mm³(or microliter) to 16 mm³(or microliter), in a range of, for example, 3 mm³(or microliter) to 16 mm³(or microliter), in a range of, for example, 7 mm³(or microliter) to 16 mm³(or microliter), in a range of, for example, 0.1 mm³(or microliter) to 10 mm³(or microliter), in a range of, for example, 0.5 mm³(or microliter) to 5 mm³(or microliter), or in a range of, for example, 0.5 mm³(or microliter) to 3 mm³(or microliter).

In some applications, it can be preferred to have an accuracy of the flow rate measurement provided by the flow meter 1 to be about 1 μL/m or less. In some embodiments, the accuracy of the flow rate measurement provided by the flow meter 1 can depend at least in part on a volume of the flow path 14 within the flow meter 1. Accordingly, it can be important to design the size of the flow path 14 to be sufficiently small so as to provide an accuracy of the flow rate measurement that is desired for its application. In some embodiments, the flow meter 1 can be designed such that an accuracy of the flow rate measurement provided by the flow meter 1 is in a range of, for example, 0.5 μL/m to 1.5 μL/m, in a range of, for example, 0.5 μL/m to 1.2 μL/m, in a range of, for example, 0.7 μL/m to 1.5 μL/m, or in a range of, for example, 0.7 μL/m to 1.2 μL/m.

The flow meter 1 can be manufactured in various manufacturing processes. A method of manufacturing a flow meter 1 according to one embodiment can include forming a housing 10. The forming the housing 10 can comprise molding a non-conductive material. The molding the non-conductive material can comprise an injection molding process. The method can also include forming a conductive material 12. The forming the conductive material 12 can comprise forming an element 12a-12e. The forming the conductive material 12 can include molding the conductive material. The molding the conducive material can comprise an injection molding process. In some embodiments, the housing 10 and the conductive material 12 can be formed using a two shot molding process. In some embodiments, the housing 10 can be formed prior to forming the conductive material 12. The method can also include a singulation process in which a plurality of flow meters are singulated.

FIG. 3A is a schematic side view of a valve 2 in a first state (e.g., a closed state) according to one embodiment. FIG. 3B is a schematic side view of the valve 2 illustrated in FIG. 3A in a second state (e.g., an opened state). The valve 2 can comprise an actuator 20 and a gate structure 22 that includes a gate 24 and a gate housing 26. In FIGS. 3A and 3B, the gate housing 26 is shown transparent to illustrate internal components of the gate structure 22. The housing 26 can have a hole 27.

The actuator 20 can actuate (e.g., open/close) the gate 24 of the gate structure 22. A portion of the actuator 20 can directly or indirectly actuate the gate 24. For example, the portion of the actuator 20 can directly apply force to a movable element 28 of gate structure 22 so as to actuate the gate 24. The actuator 20 will be described more with respect to FIGS. 4A-5C.

In FIGS. 3A and 3B, the gate 24 is fully or completely closed in the first state and the gate 24 is fully or completely opened in the second state. However, the valve 2 can comprise an intermediate state in which the gate is partially opened or closed. The intermediate state can be any state in between the fully closed state and the fully opened state. In the intermediate state, fluid can flow through the valve 2 at a non-zero flow rate less than the flow rate through the valve 2 in the fully opened state. Accordingly, an opened state can comprise any state in which the gate 24 is not fully closed.

In some embodiments, the gate 24 can be in a closed state when no external force is applied to the movable element 28, for example, when the actuator 20 is inactivated. The gate structure 22 can comprise a mechanical element, such as a spring (not shown), that keeps the gate 24 closed when no external force is applied to the movable element 28. In such embodiments, the gate 24 can open when the actuator 20 applies force to the movable element 28 that is greater than the force applied to the movable element 28 by the spring. In such embodiments, the actuator 20 can apply a vertically upward force to cause the movable element 28 to translate along a direction transverse to a lateral dimension of the actuator 20. Vertical translation of the movable element 28 can move the gate 24 upward to expose an opening 25 through which the fluid can flow in the opened state(s). The opening 25 can be exposed when at least a portion of the opening 25 and the hole 27 align with each other. When a desired amount of the fluid substance has passed through the opening 25, the actuator 20 can be inactivated, and the spring or other biased mechanical structure can force the movable element 28 downward to cause the gate 24 to occlude the hole 27 and limit flow therethrough.

FIG. 4A is a schematic cross sectional side view of the actuator 20 illustrated in FIGS. 3A and 3B in a first state. FIG. 4B is a schematic cross sectional side view of the actuator 20 illustrated in FIGS. 3A-4A in a second state. FIG. 5A is a schematic top perspective view of the actuator 20 of FIG. 4A. FIG. 5B is a schematic bottom perspective view of the actuator 20 of FIG. 4B in the second state. FIG. 5C is a schematic top perspective view of the actuator 20 of FIG. 4B in the second state.

The actuator 20 illustrated in FIGS. 4A-5C can comprise an electroosmotic (EO) pump. The actuator 20 can comprise a housing 60, a first elastic diaphragm 62 that is attached to a first side (an upper side) of the housing 60, a second elastic diaphragm 64 that is attached to a second side (lower side) of the housing 60, a spacer 66 that is positioned between the between the first side and the second side of the housing 60, a first electrode 68 that is positioned between the spacer 66 and the first elastic diaphragm 62, a second electrode 70 that is positioned between the spacer 66 and the second elastic diaphragm 64, and a porous membrane 72 positioned between the first electrode 68 and the second electrode 70. The actuator 20 can include a first chamber 74 defined at least partially by the housing 60 and the first elastic diaphragm 62, and a second chamber 76 defined at least partially by the housing 60 and the second elastic diaphragm 64. The first chamber 74 and the second chamber 76 are configured to receive a solution (e.g. reverse osmosis (RO) water). At least portions of the spacer 66, first electrode 68, and the second electrode 70 can be positioned between the first chamber 74 and the second chamber 76. In some embodiments, the portions of the spacer 66, first electrode 68, and the second electrode 70 positioned between the first chamber 74 and the second chamber 76 can provide fluid communication between the first chamber 74 and the second chamber 76. The actuator 20 can comprise contact pads 78 that can be electrically coupled to the first electrode 68 and the second electrode 70. In some embodiments, the contact pads 78 can be formed on or in a portion of the first elastic diaphragm 62 and or the second elastic diaphragm 64.

The first elastic diaphragm 62 and the second elastic diaphragm 64 can be sufficiently elastic so as to expand in response to an electroosmotic flow of a solution between the chambers 74, 76. In some embodiments, the expansions of the first elastic diaphragm 62 and the second elastic diaphragm 64 can maintain a pressure within the actuator 20. In other words, an internal pressure of the actuator 20 in the first state can be the same or generally similar to the internal pressure of the actuator 20 in the second state. For example, the second elastic diaphragm 64 can collapse inwardly and the first elastic diaphragm 62 can expand outwardly as shown. The inwardly collapsing second diaphragm 64 can avoid the generation of a vacuum in the second chamber 76, thereby lowering the pressure differential used to create the same force on the movable element 28 of the valve 2. Therefore, the first chamber 74 and the second chamber 76 can comprise expandable or deformable chambers. The first elastic diaphragm 62 and the second elastic diaphragm 64 can comprise any suitable material. In some embodiments, the first elastic diaphragm 62 and/or the second elastic diaphragm 64 can comprise silicon rubber or high consistency rubber. In some embodiments, the first elastic diaphragm 62 and the second elastic diaphragm 64 can comprise the same material or different materials.

In some embodiments, the first electrode 68 and the second electrode 70 can comprise micro-pores (not illustrated). The micro-pores can allow the solution to flow across the first electrode 68 and the second electrode 70 (between the first chamber 74 and the second chamber 76). The micro-pores are large enough for the solution to pass through but small enough for providing a sufficient magnetic field during operation of the valve 2. In some embodiments, a length l1 of a side of the micro-pore of the first electrode 68 and the second electrode 70 can be less than about 10 μm. In some embodiments, there can be a gap (not illustrated) between the first electrode 68 and the porous membrane 72. Likewise, there can be a gap (not illustrated) between the first electrode 68 and the porous membrane 72. In some embodiments, the gap can be provided by the spacer 66. In some embodiments, the gap can be in a range from 20 μm to 30 μm. The gap can be about 25 μm in some embodiments. In some applications, the gap can facilitate fluid flow between the first chamber 74 and the second chamber 76. For example, absent the gap, it may be less efficient for the solution to go through the porous membrane 72, the first electrode 68, and/or the second electrode 70 than with the gap. The gap can be sufficiently narrow such that the voltage applied to the first electrode 68 and the second electrode 70 can create a desired electroosmosis reaction.

The porous membrane 72 can comprise any suitable material. In some embodiments, the porous membrane 72 can comprise silicon, glass aluminum, or polymer. The porous membrane 72 can comprise pores. In some embodiments, a size of the pore of the porous membrane 72 can be in a range from, for example, 100 nanometer (nm) to 200 nm, in a range from, for example, 100 nm to 150 nm, or in a range from, for example, 150 nm to 200 nm. In some embodiments, the pores of the porous membrane 72 have a porosity in a range from, for example, 40% to 60%, in a range from, for example, 50% to 60%, or in a range from, for example, 40% to 50%.

The actuator 20 has a height h, lengths l1, l2 in a direction perpendicular to the height. In the illustrated embodiment, the length l1, l2 of the actuator 20 are the same. However, in some other embodiments, the lengths l1, l2 can be different. In some embodiments, the height h of the actuator 20 can be smaller than about 3 mm. Is some embodiments, the height h of the actuator 20 can be in a range of, for example, 1 mm to 3 mm, in a range of, for example, 2 mm to 3 mm, or in a range of, for example, 2.5 mm to 3 mm. In some embodiments, an area formed by the length l1, l2 can be less than about 100 mm². In some embodiments, the length l1, l2 of the actuator 20 can be about 10 mm. Is some embodiments, the length l1, l2 of the actuator 20 can be in a range of, for example, 5 mm to 15 mm, in a range of, for example, 5 mm to 10 mm, or in a range of, for example, 8 mm to 12 mm. In some applications, having the dimension of the actuator 20 relatively small can be beneficial. In such actuator 20 with small dimension can require relatively low power to operate and provide relatively fast response time for an electroosmosis reaction.

An example operation of the actuator 20 will be described with reference to FIGS. 3A-5C. In the first state illustrated in FIGS. 3A, 4A and 5A, the solution in the actuator 20 can be in an equilibrium state. For example, in some embodiments, in the first state, no external power (voltage) may be applied to the first electrode 68 and the second electrode 70. In the first state, no electroosmotic flow is created from the second chamber 76 to the first chamber 74 (or vice versa). In the first state, the first elastic diaphragm 62 and the second elastic diaphragm 64 can be relaxed. Therefore, no force is applied to the movable element 28 by the actuator 20 in the first state.

In the second state illustrated in FIGS. 3B, 4B, 5B and 5C, electrical power (voltage) is applied to the first electrode 68 and the second electrode 70. The second state comprises a state in which an external force applied by the actuator 20 is sufficient to move the movable element 28 to at least partially open the gate 24 of the gate structure 22. In the second state, a pressure difference between the first chamber 74 and the second chamber 76 created by the applied voltage can create an electroosmotic flow of the solution from the second chamber 76, through the porous membrane 72, and into the first chamber 74. The electroosmotic flow in the second state is shown with arrows in FIG. 4B. The electroosmotic flow can be controlled by controlling the applied voltage. In some embodiments, a coin cell battery can provide the voltage. In some embodiments, the actuator 20 can operate with applied voltage of less than about 5V.

Referring to FIG. 4B, the first elastic diaphragm 62 can protrude from the housing 60 in response to the electroosmotic flow of the solution. The protruded portion of the first elastic diaphragm 62 has a displacement d and a volume v. The displacement d and the volume v can be interrelated. The displacement d and the volume v can be controlled by changing the voltage applied to the first electrode 68 and the second electrode 70. For example, when a lower voltage is applied, the displacement d and the volume v can be smaller than when a higher voltage is applied. By controlling the applied voltage, the displacement d and the volume v can be controlled. In turn, a size of the exposed portion of the opening