Wide-range micro-pressure sensor
阅读说明:本技术 宽范围微压力传感器 (Wide-range micro-pressure sensor ) 是由 S.A.马什 于 2018-10-22 设计创作,主要内容包括:公开了一种微压力传感器,其包括在不同压力范围内操作的多个模块。模块包括至少两个模块层堆叠,每个模块层包括:模块主体,其具有限定隔室的壁,并且所限定的隔室划分为至少两个子隔室;用于流体进入或流出的端口,其设置在主体的第一壁中,其中主体的其余壁是实心的;膜,其固定至模块主体的覆盖隔室的第一表面;以及电极,其固定在膜的表面上。(A micro-pressure sensor is disclosed that includes a plurality of modules that operate at different pressure ranges. The module comprises at least two stacks of module layers, each module layer comprising: a module body having walls defining a compartment, and the defined compartment is divided into at least two sub-compartments; a port for fluid ingress or egress disposed in a first wall of the body, wherein the remaining walls of the body are solid; a membrane secured to a first surface of the module body covering the compartment; and an electrode fixed on a surface of the membrane.)
1. A pressure sensor, comprising:
a plurality of module stages, at least one of the plurality of module stages operating within a first pressure range and at least another of the plurality of module stages operating within a second, different pressure range, wherein each module stage comprises:
at least two module layers are stacked, each module layer comprising:
a module body having walls defining a compartment, and the defined compartment is divided into at least two sub-compartments;
a port for fluid ingress or egress disposed in a first wall of the module body, wherein the remaining walls of the module body are solid;
a membrane secured to a first surface of the module body covering the compartment; and
an electrode fixed on a surface of the membrane.
2. The pressure sensor of claim 1, wherein the sub-compartments have different volumes, and further comprising:
a first end cap connected to a first of the plurality of modules; and
a second end cap connected to a last of the plurality of modules.
3. The pressure sensor of claim 1, wherein a port of a first module layer of the at least two module layers is coupled to a fluid source and a port of a second module layer of the at least two module layers is coupled to a reference pressure, wherein a membrane of each stacked module layer has a dimension of about microns by microns to about millimeters by millimeters.
4. The pressure sensor of claim 1, wherein a first module of the plurality of modules has each module body divided into a first number of sub-compartments and a last module of the plurality of modules has each module body divided into a second number of sub-compartments, wherein the second number is greater than the first number.
5. The pressure sensor of claim 1, wherein a first module of the plurality of modules has each module body divided into a first number of sub-compartments having at least two different surface areas, and a last module of the plurality of modules has each module body divided into a second number of sub-compartments having at least two different surface areas, wherein the second number is greater than the first number.
6. The pressure sensor of claim 1, wherein the electrode of a first module layer of the at least two module layers of the first module is electrically connected to the electrode of a first module layer of the at least two module layers of the second module to provide a first electrical connection to the pressure sensor, and the electrode of a second module layer of the at least two module layers of the first module is electrically connected to a corresponding electrode of a second module layer of the at least two module layers of the second module to provide a second electrical connection to the pressure sensor that is electrically isolated from the first electrical connection.
7. The pressure sensor of claim 1, further comprising:
a capacitance measurement circuit coupled between the first and second electrical connections.
8. The pressure sensor of claim 7, further comprising:
a controller that converts the measured capacitance from the capacitance measurement circuit to a pressure value.
9. The pressure sensor of claim 1, wherein each port has a pair of holes disposed in the first wall.
10. The pressure sensor of claim 1, wherein the pressure sensor is configured to receive a fluid flow into a port of a first module layer of the at least two module layers and a port of a second module layer of the at least two module layers receives a reference pressure, wherein the fluid flow deflects the membrane in accordance with a pressure differential between the fluid flow and a reference applied to the respective port.
11. The pressure sensor of claim 1, wherein fluid flow out of the port of the module layer retracts a membrane on the compartment into the compartment, and fluid flow into the port of the module layer moves the membrane away from the compartment.
12. The pressure sensor of claim 1, wherein fluid flow out of a port of a first module layer of the at least two module layers causes its membrane to compress the compartment and a second fluid flow into a port of a second module layer of the at least two module layers disposed adjacent to the first module layer causes its membrane to expand the compartment substantially simultaneously.
13. The pressure sensor of claim 12, wherein the port of the second module layer is coupled to the reference for a negative pressure mode.
14. The pressure sensor of claim 12, wherein the port of the first module layer is coupled to the reference for overpressure mode.
15. A micro-pressure sensor, comprising:
a first module operating within a first pressure range, the first module comprising:
a first stack of a first plurality of first module layers, each first module layer comprising:
a first module body having walls defining a compartment, and the defined compartment being divided into a first plurality of sub-compartments;
a first port for fluid ingress or egress disposed in a first wall of the first module body, wherein the remaining walls of the first module body are solid;
a first membrane secured to a first surface of the first module body covering the compartment; and
a first electrode fixed on a surface of the first film;
a second module operating within a second, different pressure range, the second module being secured in a micro-pressure sensor, the second module comprising:
a second stack of a second plurality of second module layers, each second module layer comprising:
a second module body having walls defining a compartment, and the defined compartment is divided into a second plurality of sub-compartments that differ from the first plurality of sub-compartments in one or more of number and size of the sub-compartments;
a second port for fluid ingress or egress disposed in a first wall of the second module body, wherein the remaining walls of the second module body are solid walls;
a second membrane secured to a first surface of the second module body covering the compartment; and an electrode fixed on a surface of the membrane.
16. The micro-pressure sensor of claim 15, further comprising:
at least one additional module of an additional stack of additional module layers.
17. The micro-pressure sensor of claim 15, wherein the micro-pressure sensor is coupled to a capacitance measurement circuit.
18. The micro-pressure sensor of claim 15, wherein the first module is stacked with the second module, and further comprising a spacer member disposed between the first module and the second module to secure the first module to the second module.
19. The micro-pressure sensor of claim 15, wherein the first plurality of sub-compartments has one of two different sizes of sub-compartments and the second plurality of sub-compartments has one of three different sizes of sub-compartments.
20. The micro-pressure sensor of claim 15, further comprising:
a first end cap connected to a first module of the plurality of modules, and a second end cap connected to a last module of the plurality of modules.
21. A method of manufacturing a micro-pressure sensor element, the method comprising:
patterning the first sheet of material to produce a body element having a peripheral wall, and the body element is further patterned into a plurality of sub-compartments, at least some of which are defined in part by the peripheral wall of the body element, wherein the sub-compartments are also defined by an interior wall of the body element, wherein a portion of the interior wall has openings to allow fluid to enter and exit between the sub-compartments;
securing a second sheet of flexible material to the body member, the second sheet being flexible relative to the first sheet of material, the second sheet having a conductive surface layer to provide a composite laminate structure secured to an interior wall defined in the body member to create the module layer member.
22. The method of claim 21, further comprising:
the conductive layer on the second sheet is patterned into isolated regions to provide electrodes on the second sheet.
23. The method of claim 21, further comprising:
the conductive layer on the second sheet is patterned to produce electrodes with tabs for connection to external circuitry through metal vias.
24. The method of claim 21, further comprising:
creating a plurality of module layer members each having a body member patterned into a plurality of sub-compartments, a second sheet of flexible material secured to the body member and having a conductive surface layer and having a tab;
forming a stack of module layer components secured together; and
the stack of module layer components is secured between a pair of end caps.
25. The method of claim 24, wherein patterning the first sheet further comprises:
patterning the first sheet to provide a hole through a portion of a peripheral wall of the body;
metal vias are formed through the holes to contact the vias of the corresponding ones of the module layer components.
26. The method of claim 23, further comprising:
the first sheet is patterned to create ports in a first perimeter wall of the body member.
27. The method of claim 21, wherein patterning further comprises:
an end cap is applied to at least one module layer.
Technical Field
This description relates to pressure sensor devices and systems.
Background
The pressure sensor detects or measures the fluid pressure, i.e. the force exerted by the fluid, which is the force required to resist the expansion of the fluid. Pressure sensors are used in various control and monitoring applications and can be used to indirectly measure other physical quantities such as fluid flow, fluid velocity, and altitude. Typically, pressure sensors are manufactured using a variety of techniques, each of which finds use in terms of performance, application suitability, and cost considerations.
A typical pressure sensor includes a transducer that generates an electrical signal as a function of pressure applied to the transducer, which is an example of a force accumulator-type pressure sensor. Force collector types use force collectors (such as diaphragms, pistons, etc.) to measure strain (or deflection) caused by forces applied to the force collectors. Types of force collectors include piezoresistive strain gauge types that use the piezoresistive effect to detect strain due to applied pressure and piezoelectric types that use the piezoelectric effect in certain materials such as quartz, certain ceramics, and certain polymers.
The other type is a capacitive type, which uses a diaphragm and a pressure chamber to create a variable capacitor to detect strain due to applied pressure. Common techniques use metal, ceramic and silicon diaphragms. Such sensors can be manufactured using silicon MEMS (micro electro mechanical systems) technology.
Disclosure of Invention
According to one aspect, a pressure sensor includes a plurality of module levels, at least one of the plurality of module levels operating within a first pressure range and at least another of the plurality of module levels operating within a second, different pressure range, wherein each module level includes at least two stacks of module layers, each module layer including: a module body having walls defining a compartment, and the defined compartment is divided into at least two sub-compartments; a port for fluid ingress or egress disposed in a first wall of the module body, wherein the remaining walls of the module body are solid; a membrane secured to a first surface of the module body covering the compartment; and an electrode fixed on a surface of the membrane.
According to another aspect, a micro-pressure sensor includes a first module that operates within a first pressure range, the first module including a first stack of a first plurality of first module layers, each first module layer including: a first module body having walls defining a compartment, and the defined compartment is divided into a first plurality of sub-compartments; a first port for fluid ingress or egress disposed in a first wall of the first module body, wherein the remaining walls of the first module body are solid; a first membrane secured to a first surface of the first module body covering the compartment; and a first electrode fixed on a surface of the first film. The micro pressure sensor also includes a second module that operates within a second, different pressure range, the second module being secured in the micro pressure sensor, the second module including a second stack of a second plurality of second module layers, each second module layer including: a second module body having walls defining a compartment, and the defined compartment is divided into a second plurality of sub-compartments that differ from the first plurality of sub-compartments in one or more of number and size of the sub-compartments; a second port for fluid ingress or egress disposed in a first wall of the second module body, wherein the remaining walls of the second module body are solid walls; a second membrane secured to a first surface of the second module body covering the compartment; and an electrode fixed on a surface of the membrane.
Other aspects include methods of manufacture.
Micro pressure sensors may be used to perform pressure sensing for various industrial, medical, and biological applications. The micro-pressure sensor can be manufactured using a relatively inexpensive technology, thereby providing an inexpensive micro-pressure sensor for various applications. In a particular embodiment, the micro-pressure sensor is fabricated using roll-to-roll manufacturing techniques. The micro-pressure sensor is operable over a relatively wide pressure range and has a high sensitivity to pressure changes over a wide pressure range relative to micro-pressure sensors constructed from standard sized compartments.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Drawings
Fig. 1, 2, 3A and 3 are schematic functional cross-sectional views at the module level of a wide-range micro-pressure sensor, showing the micro-pressure sensor in a rest mode, an overpressure mode, a greater overpressure mode and a negative pressure mode, respectively.
Fig. 4 is an isometric view of a micro-pressure sensor including multiple repeatable module layers based on the concepts described in fig. 1-3.
Fig. 4A is an isometric view of a module of the micro-pressure sensor of fig. 4.
Fig. 5 is a simplified schematic diagram illustrating an equivalent circuit model for the capacitance of the modular micro pressure sensor of fig. 4.
6A-6C are isometric views of different exemplary body layer patterns for forming sub-compartments within a modular micro-pressure sensor.
FIG. 7 is an isometric view of the modular micro pressure sensor of FIG. 4 showing the removal of multiple layers.
FIG. 8 is an isometric view of the modular micro pressure sensor of FIG. 4 showing the removal of all layers except for the spacer member and end caps.
Fig. 9 is a table showing capacitance versus membrane separation and pressure.
Fig. 10 is a graph of pressure versus capacitance.
FIG. 11 is a graph of capacitance versus pressure and diaphragm spacing versus pressure.
Fig. 12 is a conceptual diagram of a roll-to-roll processing configuration.
Fig. 12A is a conceptual diagram of some exemplary roll-to-roll processing stations.
Fig. 13A-13C are views of the roll-to-roll processing of the structure of fig. 13, showing the pattern of fig. 6A.
Fig. 14A-14B are views depicting details of via conductors.
Detailed Description
SUMMARY
The micro-pressure sensors described herein are made using micro-fabrication methods and can be used to sense pressure in a variety of industrial, commercial, medical, and biological applications. Micro pressure sensors are manufactured on a micro/millimeter scale. Various manufacturing techniques are disclosed.
One type of micro-pressure sensor is a narrow pressure range micro-pressure sensor as described in published patent application US-2018-0038754-a1, assigned to the assignee of the present application by himself, which is incorporated herein by reference in its entirety. A narrow range micro-pressure sensor means that a given module will operate within a narrow pressure range relative to a wide range micro-pressure sensor. The micro-pressure sensor incorporated by reference application has a single chamber divided into a plurality of compartments. Within a given pressure range, each compartment experiences and responds to the same pressure. The narrow range type is a micro-pressure sensor (referred to herein as a narrow range micro-pressure sensor) having high sensitivity within a relatively narrow pressure range.
Described below is another type of micro-pressure sensor that has high sensitivity over a wide pressure range, referred to herein as a wide-range micro-pressure sensor. Two types of wide-range micro-pressure sensors are described, namely a wide-range
Wide-range micro-pressure sensor
Referring to fig. 1, a
As will be shown in more detail in fig. 6A-6C, each
A first set of
As described below, multiple sub-compartments, such as sub-compartments 23a-23b, will provide different degrees of sensitivity to different pressures and pressure ranges within a single compartment.
In fig. 1, the ports are shown on opposite sides. In many embodiments, ports on opposite sides are desirable, but not required. In other embodiments, the ports may be on adjacent sides or indeed on the same side, as long as the port acting as an inlet or input port is separate from the port acting as an outlet or output port, coupling the ports to different vessels that provide the fluid whose pressure is being measured and used as a reference. A compartment will have only one inlet or one outlet, but not both.
As shown in fig. 1, this arrangement of solid walls at one end and a first one of the first or second set of ports at the opposite end is alternating, such as shown for the
The
In the embodiments discussed below, the pressure is relative to the ambient pressure of the ambient air. However, other references may be used.
Also, in the discussion that follows, a wide-range micro-pressure sensor is relative to a narrow-range micro-pressure sensor. While the following discussion will focus on a wide-range micro-pressure sensor, it will be helpful to first define a narrow-range micro-pressure sensor and discuss the general features and operating characteristics common to both narrow-range and wide-range micro-pressure sensors.
The narrow range micro pressure sensor comprises one or more standard
In contrast to the wide-
For narrow or wide range micro-pressure sensors, although six
Each
When an external fluid is fed to the
When activated, by applying pressure, the
A change in volume may be considered as an alternative way of representing a change in pressure. The capacitive properties are provided by a pair of adjacent electrodes separated by a dielectric, for example the dielectric properties of the contents (i.e. fluid) and/or the membrane of the compartment.
The capacitor is effectively provided by the combination of a pair of electrodes on a pair of adjacent membranes separated by a distance from the respective compartment. The capacitive characteristics of such an effective capacitor are determined by the dielectric constant provided by one of the pair of adjacent membranes, the dielectric constant of the fluid in the compartment, the area of the electrodes, and the distance separating the electrodes, e.g., typically at least approximately by the formula for a parallel plate capacitor, expressed as:
C=r 0a/d, wherein,
c is capacitance in farad units;
a is the overlapping area of the two electrodes, in square meters;
ris the dielectric constant of the material between the electrodes (sum of the dielectric constants of the membrane and the fluid);
0is an electric constant of0About 8.854 × 10-12 F.m-1), and
d is the spacing between the plates in meters.
Where d is sufficiently small relative to the minimum chord of a.
A controller (see fig. 2, 3) that is part of the capacitance measurement circuit or a separate circuit references a table/algorithm to convert measured capacitance units to pressure units. Many techniques may be used to measure and detect this change in capacitance over the large capacitance provided by the
In some embodiments, the distance between two
The
In other embodiments, the ports may be on adjacent sides or indeed on the same side, as long as the ports that serve as inlet or input ports are separate from the ports that serve as outlet or output ports, by coupling these ports to different vessels that provide the fluid whose pressure is being measured and used as a reference. The depicted
Referring to fig. 2, the end compartments 21a and 21g are shown compressed by applying an overpressure from the fluid source 26 (higher pressure at the
Compression occurs in the
In overpressure operation (fig. 2), the
However, as the overpressure increases, the increased overpressure will cause additional bending of the
Fig. 2A shows the arrangement of fig. 2 (see fig. 2 for a description of the reference numerals not mentioned), but the overpressure is greater than in fig. 2, which is sufficient to cause the
Referring now to FIG. 3, under negative pressure (lower pressure than a reference, e.g., reduced to vacuum pressure), at the ports serving as
As the
In negative pressure operation (fig. 3), the
Like fig. 2, those portions of the
Removal of the overpressure or underpressure applied to the port returns the
Thus, the
Comparing fig. 2 and 3, they show that two operating states of the same
Electrodes (not explicitly shown in fig. 1-3) are on the
Micro-pressure sensors having the above-described features can be manufactured using various methods such as MEMS processing techniques and so-called roll-to-roll (R2R) processing. The material for the
Sensor body-the material for the body can be defined as desired. Typically, the material needs to be strong or stiff enough to hold its shape to create the compartment volume. In some embodiments, the material is etchable or photosensitive so that its features can be defined and processed/developed. It is sometimes also desirable for the material to interact well with other materials in the sensor, for example to adhere. Furthermore, the material is electrically non-conductive. Examples of suitable materials include SU8 (negative epoxy resist) and PMMA (polymethyl methacrylate) resist.
Membrane-the material of this part forms the tympanic membrane structure, which can be filled and drained in the chamber. Thus, the material is required to bend or stretch back and forth over a desired distance and to have elastic properties. The membrane material is impermeable to the fluid of interest, including gases and liquids, is electrically non-conductive, and may have low or high breakdown voltage characteristics. Examples of suitable materials include silicon nitride and teflon. Others are also possible.
Electrode-the material of the electrode is electrically conductive. Because the electrodes do not conduct substantial current, the material may have a high electrical sheet resistance, although high resistance characteristics are not necessarily required. The electrode is subject to bending and stretching of the membrane, and therefore, it is desirable that the material be flexible to cope with bending and stretching without fatigue and failure. In addition, under operating conditions, the electrode material and the membrane material adhere well, e.g. do not delaminate from each other. Examples of suitable materials include very thin layers of gold and platinum. Others are also possible.
Electrical interconnection-the voltage from the capacitance measurement circuit is conducted to the electrodes on each membrane of each compartment. Conductive materials such as gold and platinum may be used to establish a conductive path to these electrodes.
Other materials-when MEMS processing is used in the fabrication of micro-pressure sensors, sacrificial filler materials, such as polyvinyl alcohol (PVA), may be used. Sacrificial fill material may also be used for R2R processing. In some embodiments, a solvent is used during the manufacturing process, which may place additional requirements on various build materials of the micro-pressure sensor. Some circuit components may be printed onto the film. Typically, although certain materials have been specified above, other materials having similar properties to those mentioned may also be used.
Referring now to fig. 4, a modular wide-
Modular wide-
Each of the three
Referring to fig. 4A, the module layer (overall 105) generally includes a bulk layer 111a, the bulk layer 111a supporting a membrane 111b, the membrane 111b carrying an electrode 111c and providing (with another membrane on another module) a compartment. The body layer 111a has a pair of
The electrodes may be pre-prepared pieces to be attached to other elements, and the electrodes may be formed directly onto those elements, for example by printing or other techniques discussed below. Thus, a plurality of, e.g., two, three, or any desired number of modules and module layers are stacked upon one another to form a plurality of intermediate compartments in the modular stacked
Each of the three
Also shown in fig. 4 is a capacitance measurement circuit and controller (as shown in fig. 2) coupled to the electrodes (represented by
Referring now to FIG. 5, each
One mechanism that provides high sensitivity over a wide pressure range for a given standard size chamber is to have membranes with different stiffness from one another. A mechanism for providing different "effective" stiffness to the membrane by providing different pore sizes within the compartment to effectively stiffen the membrane to a greater or lesser extent is now described. Generally, the stiffer the membrane, the greater the pressure required to bend the membrane.
Referring now to FIGS. 6A-6C, three different patterns for forming the body layer to provide sub-compartments within the body layer are shown. On each set of body layers (e.g. one or more body layers in a stack) a membrane is provided that surrounds the sub-compartments. The membrane carries electrodes (neither shown) which, together with the bulk layer, provide the module layer 105 (shown in fig. 5). The body layer is patterned to provide a complex pattern of sub-compartments. Although the complex pattern for each compartment can vary, the exemplary patterns shown in fig. 6A-6C depict general concepts that can be followed in selecting a pattern. For example, consider that each sub-compartment is enclosed in a frame of body layer material, that is, each sub-compartment is substantially enclosed by body layer material, but for accessing such sub-compartments. By being surrounded by a frame of bulk layer material provides a suitable surface through which the film can adhere to the bulk layer.
FIG. 6A is an example of a complex pattern of sub-compartments of two different sized regions. One sub-compartment 23a is a large sub-compartment and the other is twelve smaller sub-compartments 23b, which are substantially the same area with respect to the sub-compartment 23 a. In fig. 6A, the large sub-compartment 23a and four relatively small sub-compartments 23b are fluidly connected to
FIG. 6B is an example of a complex pattern of three differently sized regions of sub-compartments. Two sub-compartments 24a are large sub-compartments, four sub-compartments 24b are smaller relative to sub-compartment 24a, and two further sub-compartments 24c are smaller relative to sub-compartment 24 b. In fig. 6B, one of the
FIG. 6C is an example of a complex pattern of sub-compartments having four different sized regions. Two sub-compartments 25a are relatively large sub-compartments, two sub-compartments 25b are smaller relative to sub-compartment 25a, two further sub-compartments 25c are smaller relative to sub-compartment 25b, and four
In fig. 6A-6C, the sub-compartments may be completely patterned by the body layer material, i.e. by providing open pores in the module layer, i.e. pores (covered by a membrane), and in some cases it may be necessary or desirable to pattern only by the body layer material, providing shallow regions (which are covered by a membrane), rather than pores within the body layer, the body layer material remaining on the back side of the module. This method of modifying the effective stiffness of each compartment is relatively easy to implement in the processing techniques discussed below.
For reference again, standard sized compartments may be defined. Although a standard size compartment can be any size, it is nominally 1.5mm long by 1.5mm wide by 50 microns high for purposes of discussion herein. Each complex patterned compartment is formed from a microsensor host material by patterning the material to form a plurality of sub-compartments that define a particular complex pattern in a standard sized compartment (examples of which are shown in fig. 6A-6C). That is, within a "standard size compartment" are a plurality of sub-compartments having a selected size (surface area) relative to a reference standard size compartment.
Referring again to the standard-sized compartments, a complex pattern compartment may be any pattern that leaves the host material within the portion of the otherwise standard-sized compartment that forms the plurality of sub-compartments within the standard-sized compartment.
The membrane carries electrodes, and the compartment is defined by a pair of membranes, wherein each membrane carries a corresponding electrode.
With the complex pattern cells of fig. 6A-6C, fluid, e.g., air, enters through
Returning now to FIG. 4A and considering FIG. 6A, assume that the module of FIG. 6A is used in
Up to 2psi, the amount of deflection of the membrane 105b will be relatively minimal. This is because the size (surface area) of the sub-compartments 23a and 23b is selected to be minimally responsive to pressures below 2 psi. Sensitivity (capacitance change versus pressure change) can be modeled with knowledge of the young's modulus of the membrane/electrode combination, the surface area of the pores, the material dielectric constant between the electrode pair, the electrode size, and the pore height, generally as described above. At 2psi or slightly higher, the portion of the membrane above the sub-compartments 23a, 23b will begin to bend.
However, the amount of bending of the membrane 105b at 2psi or slightly above the sub-compartment 23a will be much greater than the amount of bending at the sub-compartment 23 b. The relative amount of bending will be related to the difference in surface area of the film portions on the sub-compartments 23a and 23b, as the film 105b is secured to the body layer along the frame and interior portions of the body, effectively providing a single film on each sub-compartment 23a, 24 a. At some pressure above 2psi but below 4psi, the membrane portion on sub-compartment 23a will no longer respond and membrane 105b and the corresponding membrane 105b from the
However, the membrane portion on the sub-compartment 23b will still respond to pressure changes and will therefore provide a concomitant change in capacitance. Thus, each different pair of electrodes on the film covered electrodes effectively provides a fixed or bulk capacitance and a variable capacitance in parallel. Each module and each sub-compartment also effectively provide a fixed or bulk capacitance and a variable capacitance, all of which are connected in parallel and thus added together to provide an overall fixed or bulk capacitance and an overall variable capacitance. Design considerations to consider include the following provisions: none of the sub-compartments should exhibit a maximum pressure which would cause the membrane to bend and exceed the elastic limit of the membrane material.
Thus, each
Fig. 7 shows the modular wide-
FIG. 8 shows modular wide-
Returning to fig. 4, modular wide-
Each membrane of the
In addition, because each membrane carries only one electrode and the capacitance is being sensed, the capacitors, and more particularly the electrodes, can be connected such that the capacitors are connected in parallel. Capacitors connected in parallel add capacitance. Thus, by connecting the capacitors formed by the membrane and electrode pair in parallel, the modular wide-
The membrane, end cap and body may be the same size, and the electrode may be of smaller size than the membrane or other element. In some embodiments, the membrane has a size of about microns by microns to about millimeters by millimeters and a thickness of about 5 microns. The body has an outer dimension of about microns by microns to about millimeters by millimeters, a thickness of about 50 microns, and an inner dimension of from about microns by microns to about millimeters by millimeters. The thickness of the body defines the nominal size of the compartment (similar to the compartment of fig. 1). The dimensions of the electrodes substantially correspond to the internal dimensions of the body. In some embodiments, the electrode has a thickness of about 2.25mm2And a thickness of about 0.01 microns (100 angstroms). The assembled module layers are shown in fig. 4A.
Referring now to fig. 9, a table of exemplary calculated values is shown with capacitance values calculated in picofarads for a standard micro-pressure sensor (incorporated by reference) for one module and seven module micro-pressure sensors, where the spacing (distance between electrodes) and corresponding pressure are expressed in centimeters of water. At 50 micron intervals (at rest), the capacitance of one capacitor is 0.38pF, the capacitance of seven capacitors is 2.26pF, and the water pressure is 0.00 cm. Similar features may be provided for
Fig. 10 and 11 show exemplary graphs of a standard micro-pressure sensor (from the one incorporated by reference application), where fig. 10 plots pressure (in centimeters of water) against capacitance in pF for one and seven modules (capacitors). Using seven modules will provide a larger capacitance range over the same pressure range than the capacitance range of one capacitor (single stage module). Similar features may be provided for
Fig. 11 shows that the capacitance versus pressure and spacing versus pressure is substantially linear over the operating range of a standard micro-pressure sensor (incorporated by reference). Similar features may be provided for
Roll-to-roll processing to produce micro-pressure sensors
Referring to fig. 12, 12A, a conceptual diagram of a roll-to-roll processing line is shown. The process line includes a plurality of stations, such as station 1 through station n (which may be or include closed sub-compartments), where deposition, patterning, and other processes are performed. Thus, high level processing can be additive (adding material just where needed) or subtractive (removing material where not needed). The deposition process includes evaporation, sputtering and/or Chemical Vapor Deposition (CVD) as well as printing as desired. The patterning process may include a variety of techniques, as desired, such as scanning laser and electron beam pattern generation, machining, optical lithography, gravure printing, and flexographic (offset) printing, depending on the resolution of the patterned features. Ink jet printing and screen printing can be used to place functional materials, such as conductors. Other techniques such as punching, embossing and embossing may also be used.
The original roll of stock material is a web of flexible material. In a roll-to-roll process, the flexible material web may be any such material, and is typically glass or plastic or stainless steel. Although any of these materials (or others) may be used, plastic has the advantage of being less costly than glass and stainless steel. The specific material will be determined based on the application of the micro-pressure sensor. In applications, materials such as stainless steel or other materials that can withstand temperatures, such as polytetrafluoroethylene and other plastics that can withstand temperatures, will be used.
For the structures shown in FIGS. 1-4: stations are provided in the roll-to-roll processing line according to the required processing. Thus, while the end caps and top caps may be formed on a mesh or plastic sheet in one embodiment, the end caps and top caps are provided after the formation of the micro pressure sensor stack, as will be described.
A plastic web is used to support the body by depositing material on the web at a deposition station and then at a patterning station. The body is formed at a forming station. A web having a body has a film deposited over the body at a station. An electrode is deposited over the film at a deposition station, which is patterned at a patterning station. A membrane sheet with patterned electrodes supported on a membrane is disposed on the body. Electrical interconnections for connecting to the electrodes on each membrane are provided by depositing conductive materials (or conductive inks such as silver inks) such as gold, silver and platinum layers. In some embodiments, some circuit components are printed onto the film.
The roll with the micro-module cells (body and membrane with electrodes and electrical connections) is cut into small pieces and the micro-module cells are collected, assembled into a stack of micro-modules, and packaged by including end caps and top caps to provide the
The film material needs to be bent or stretched back and forth over a desired distance and should therefore have elastic properties. The membrane material is impermeable to fluids including gases and liquids, is electrically non-conductive, and has a high breakdown voltage. Examples of suitable materials include silicon nitride and teflon.
The material of the electrodes is electrically conductive. The electrodes do not conduct a significant amount of current. The electrode is subject to bending and stretching of the membrane, and therefore it is desirable that the material be flexible to handle bending and stretching without fatigue and failure. In addition, under operating conditions, the electrode material and the membrane material adhere well, e.g. do not delaminate from each other. Examples of suitable materials include, for example, gold, silver, and platinum layers (or conductive inks, such as silver ink, etc.). The release material may be used to allow movement of the valve. Suitable release materials include, for example, the sacrificial fill materials described above.
Referring to fig. 13A-13C, an alternative roll-to-roll processing method is shown that provides a
Referring to fig. 13A, a sheet of flexible material such as glass or plastic or stainless steel is used as the mesh. For a specific implementation of the micro-pressure sensor, the material is a plastic sheet, such as polyethylene terephthalate (PET). The sheet and hence the bulk layer was a 50 micron thick PET sheet. Other thicknesses may be used, for example the thickness of the sheet and body layers may be between, for example, 25 microns to 250 microns (or more), while the nominal 5 microns of the film may be, for example, about 10% of the thickness of the body. The thickness is determined based on the desired characteristics of the micro-pressure sensor and the handling capacity of the roll-to-roll processing line, and these considerations will provide practical limits on the maximum thickness. Also, the minimum thickness depends on the desired characteristics of the micro-pressure sensor to be constructed and the ability to process very thin sheets in a roll-to-roll processing line.
For the
Referring now to fig. 13B, the sheet with defined compartments is laminated to a second sheet, for example a 5 micron thick PET sheet, with a 100A Al metal layer on the top surface of the sheet at a lamination station. The second sheet forms a film over the body provided by the defining features of the sub-compartments. The second piece is also machined to provide alignment holes (not shown).
The second sheet is also provided with a plurality of randomly dispersed apertures or viewing ports (not shown) in some areas that will be aligned with the body structure prior to laminating the second sheet to the first sheet. These randomly dispersed holes are used by the machine vision system to reveal and identify potential features of the body elements on the first sheet. The data is generated by noting the identified features on the first sheet through random holes. These data will be used to align the third ablation station when the electrodes are formed from the layer on the body.
In the areas where there is plastic on the first sheet and plastic on the second sheet, the second sheet is laminated to the first sheet and thus bonded (or adhered) to the first sheet. At this point, a composite sheet of repeatable cells of the micro-pressure sensor is formed, but without electrodes formed from layers on the film.
The machine vision system generates a data file that the laser ablation system uses in aligning the laser ablation station with the mask (or direct write) so that the laser beam from the laser ablation system provides electrodes according to the mask, with the electrodes being in registration with respective portions of the body. The electrodes are formed by ablating metal away in areas that are not part of the electrodes and conductors, leaving isolated electrodes and conductors on the sheet. Thus, by using a machine vision system to view features on the front side of the laminate structure, registration of the patterned electrode with the body is provided, thereby providing positioning data for the laser ablation system used to align the laser beam with the mask, using techniques common in the art.
Referring now to fig. 13C, the composite sheet is fed to a laser ablation station to form an electrode by ablating a 100A ° Al layer deposited on the second sheet forming the film. The composite sheet is patterned according to a mask to define electrodes on respective regions of the body. The ablation station ablates metal from the metal layer, leaving isolated electrodes on the sheet.
A jig (not shown) that may include four vertical posts mounted on a horizontal base is used to stack the individual cutting dies. An end cap (e.g., a 50 micron PET sheet with a metal layer) is placed on the jig, and a first repeatable unit is placed over the end cap. The repeatable unit is held in place on the jig by spot welding (applying a localized heat source). Each repeatable unit is spot welded as it is stacked on the previous repeatable unit. The stack is provided by having ports on one side of the stack and ports on the other side of the stack, and staggered due to the arrangement of the valves, so as to have a solid surface separating each port in the stack (see figure 6). Once stacking is complete, a top cover (not shown) may be provided. The stacked units are fed to a lamination station, not shown, where the stack is laminated, laminating all the repeatable units and the cover layer together. The end caps and top cover may also be part of the package. Otherwise, the sets of repeatable units may be laminated or welded in pairs. Other stacking techniques for assembly with or without alignment holes are also possible.
Referring now to fig. 14A, 14B, details of via conductors interconnecting patterned electrodes on a module (generally 105) as described above are shown. In these figures, only the electrodes and tabs are shown with via conductors. The body portion is not shown for ease of understanding of the via conductor structure. The via conductors are castellated, i.e., have a relatively wide area contacting the electrode tabs and a relatively narrow area through the holes in the electrodes. This arrangement is provided by making the aperture in the body portion larger than the aperture through the electrode portion. This can be done at the patterning level of the body and the electrodes, respectively. The via conductor is formed by introducing the above-described conductive ink into the hole.
Elements of different embodiments described herein may be combined to form other embodiments not specifically set forth above. Elements may be excluded from the structures described herein without adversely affecting their operation. In addition, various separate elements may be combined into one or more separate elements to perform the functions described herein. Additionally, while the pressure modules are shown in a stacked form, other arrangements are possible, including pressure modules adjacent to and spaced apart from each other, so long as the pressure modules are equipped with respective end caps and have inlets and outlets fed from a common pressure source and a common reference. In addition, the electrodes on the membrane may be patterned to correspond to the underlying patterned sub-compartments (with an accompanying increase in the number of capacitances that need to be measured and interconnected), and the membrane of a given module may be a single membrane, or may be divided into individual membranes corresponding to the underlying patterned sub-compartments. Other embodiments are within the scope of the following claims.
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