Pressure sensor and pressure determination method

Abstract

The invention relates to a pressure sensor (100) comprising an electromechanical element (120) configured to change its shape in accordance with a pressure (150) applied to the pressure sensor (100) and to output an electromagnetic characteristic (160) based on the shape change (151); and a frame element (110) having a surface (112) against which the electromechanical element (120) is pressed by an applied pressure (150) to cause a shape change (151).

Description

Background Art

[0001] The invention relates to a pressure sensor, a sample separation device and a pressure determination method.

[0002] Known pressure sensors for measuring the pressure of liquids involve the introduction of force via a separation membrane with considerable inherent stiffness. On the one hand, the membrane must be elastic for the transmission of the pressure without damping, and on the other hand, the force transducer must have mechanical stability, which is characteristic of solid-state behavior. In order to meet these conflicting requirements, oil is usually introduced downstream of the separation membrane. The force transducer is located on the wall side in the oil. Such known pressure sensors are bulky in terms of size and construction and are relatively costly to produce. Summary of the invention

[0003] The object of the invention is to provide a compact and inexpensive pressure sensor which is particularly advantageous for use in a sample separation device. This object is achieved by the independent claim. Further exemplary embodiments are shown in the dependent claims.

[0004] According to an exemplary embodiment of the present invention, there is provided a pressure sensor comprising: (i) an electromechanical element configured to change a shape of the electromechanical element according to a pressure applied to the pressure sensor and output electromagnetic characteristics based on the shape change; and (ii) a frame element having a surface against which the electromechanical element is pressed by the applied pressure to cause the shape change.

[0005] According to another exemplary embodiment of the present invention, a sample separation device for separating a fluid sample in a mobile phase into components is provided, wherein the sample separation device comprises a pressure sensor having the above-mentioned characteristics for determining the pressure of the mobile phase and / or the fluid sample. The pressure sensor can be arranged in front of a pumping system of the sample separation device, in particular upstream of the pumping system.

[0006] According to another exemplary embodiment, a pressure determination method is provided, wherein the method includes: (i) providing a pressure sensor having an electromechanical element and a frame element; (ii) measuring electromagnetic properties of the electromechanical element, wherein the electromagnetic properties depend on a shape change of the electromechanical element, wherein the shape change is caused by a pressure applied to the pressure sensor causing the electromechanical element to press against a surface of the frame element; and (iii) detecting the applied pressure based on the measured electromagnetic properties.

[0007] In the context of the present application, the term "pressure sensor" may be understood in particular as a device for determining the pressure of a liquid and / or a gas and / or for determining properties related to these pressures. For example, the pressure may be determined indirectly by measuring electrical properties such as capacitance, inductance or charge. Pressure sensors are also suitable for determining the pressure exerted by solid bodies.

[0008] A pressure sensor may have a "sensitivity" or "responsiveness", in particular the ability to resolve small pressure differences. Sensitivity may be defined as the change in the value of an output variable of the measuring device relative to the value of an input variable causing its change. The sensitivity may be determined by a characteristic curve or sensor characteristic of the pressure sensor, such as an at least partially linear characteristic curve or an exponential characteristic curve. A pressure sensor may also have a "measuring range", which is characterized by the maximum and / or minimum pressure that can be determined by the pressure sensor.

[0009] In the context of the present application, the term "electromechanical element" may particularly denote a component of a pressure sensor, which outputs an electromagnetic variable, such as a capacitance, in response to a mechanical variable, in particular a pressure, acting on the electromechanical element. The electromagnetic variable may depend on the acting mechanical variable. The pressure applied to the electromechanical element may lead to a change in the shape of the electromechanical element, which shape change at least partially leads to a corresponding change in the electromagnetic variable. The electromechanical element may be configured, for example, as a block, in particular a cylindrical block, or as a membrane, in particular a circular membrane.

[0010] The electromechanical element may comprise a material including an electroactive polymer. In the context of the present application, an "electroactive polymer" (EAP) may particularly denote a polymer that changes shape by applying an electrical voltage and / or a polymer characterized by electromagnetic variables associated with the change in shape of the polymer. Advantageously, such an electroactive polymer may be elastic, in particular capable of achieving a large extension with free formability, so that small pressure changes can be resolved. Preferably, such an electroactive polymer may be formed as a dielectric elastomer, in particular a silicone elastomer or an acrylic elastomer. Descriptively speaking, an electroactive polymer between two or more electrodes may form a capacitor, the capacitance of which may depend on the change in shape of the electroactive polymer between the two or more electrodes. For example, due to the high ductility of the electroactive polymer, such a capacitor has a particularly high responsiveness to pressure changes.

[0011] The electromechanical element may include a dielectric elastomer sensor element (DES). The dielectric elastomer sensor element may be configured to convert mechanical work into electromagnetic properties, such as electrical energy, and / or vice versa. The dielectric elastomer sensor element may include an elastomer layer, which is arranged between two electrodes, in particular between elastic electrodes. The material of the elastomer layer may be incompressible, or at least approximately incompressible. The material may have a low dielectric constant. The material may be particularly ductile, for example having a unidirectional elongation greater than 10%, in particular greater than 30%, and in particular greater than 100%. The unidirectional elongation may be less than 300%. It may be within the range of 300%, in particular with a deviation of less than 10%. The elongation may be defined as the maximum length change of the material without breaking or tearing. The material may include or consist of at least one of a silicone elastomer and an acrylic elastomer. Descriptively speaking, the dielectric elastomer sensor element may be a flexible capacitor.

[0012] In the context of the present application, the term "change in shape" may particularly denote a change in the outer shape of the body, such as an extension and / or compression of the body. The change in shape may be incompressible or almost incompressible, i.e. the volume remains unchanged. For example, the change in volume in the change in shape may be less than 10% of the initial volume, in particular less than 1% of the initial volume. The change in shape may also include a change in volume of more than 10%.

[0013] In the context of the present application, the term "electromagnetic property" may particularly denote any electrical or magnetic property of an electromechanical element. The electromagnetic property may be or include at least one of capacitance, inductance and charge. The fact that the electromagnetic property is based on a shape change particularly means that the property depends on and / or is associated with the shape change. For example, when the electromechanical element forms a capacitor, the shape change may result in a capacitance change.

[0014] In the context of the present application, the term "frame element" may particularly denote a part of the pressure sensor that at least partially surrounds and / or at least partially covers the electromechanical element. The frame element may be a cover or a lid that at least partially covers the electromechanical element. The frame element may comprise a groove, in particular a blind hole or a through hole. For example, the groove may be a blind hole having a bottom surface or a base surface. The bottom surface may be a surface against which the electromechanical element is pressed by the applied pressure to be measured. The groove may be cylindrical and / or the bottom surface may be circular. The groove may have a shape complementary to the electromechanical element, so that the electromechanical element may be at least partially, in particular completely, introduced into the groove. When the electromechanical element is introduced into the groove, only the surface of the electromechanical element on which the pressure is applied by the liquid or gas may be completely exposed. The pressure may be transmitted by a separation element, in particular a membrane, covering this surface.

[0015] The "surface of the frame element against which the electromechanical element is pressed" may be opposite to the surface of the electromechanical element against which the liquid or gas exerts pressure, relative to the electromechanical element. It may be the surface of the groove, and may in particular or include the bottom surface of the groove. The electromechanical element may be pressed against the surface of the frame element by the corresponding surface of the electromechanical element. The corresponding surface may be opposite to the surface of the electromechanical element against which the liquid or gas exerts pressure, and / or opposite to the completely exposed surface of the electromechanical element.

[0016] In the context of this application, the term "measurement" may refer to direct measurement of a variable and / or indirect determination from one or more measured values ​​associated with the variable to be measured. In the context of this application, the term "determination" may include calculation of a variable.

[0017] In the context of the present application, the term "sample separation device" may particularly denote a device capable of and configured to separate a fluid sample (e.g., separate it into different components). For example, sample separation may be performed by chromatography or electrophoresis. For example, the sample separation device may be a liquid chromatography sample separation device.

[0018] In the context of the present application, the term "fluid sample" particularly denotes a medium containing the actual substance to be analyzed (eg a biological sample, such as a protein solution, a pharmaceutical sample, etc.).

[0019] In the context of the present application, the term "mobile phase" particularly refers to a fluid (further particularly a liquid) used as a carrier medium for conveying a fluid sample from a fluid driver (e.g. a piston pump) to a sample separation device. For example, the mobile phase may be a (e.g. organic and / or inorganic) solvent or solvent combination (e.g. water and ethanol).

[0020] According to an exemplary embodiment of the present invention, a pressure sensor can be created which can resolve small pressure changes below the exposed surface of an electromechanical element of small diameter, wherein the exposed surface can be separated from the sample by a separation element (e.g. a membrane). The pressure sensor can have a higher sensitivity and / or a larger measuring range for pressure measurement. Due to the simple construction, it can be implemented in a particularly compact manner. In addition, it can be manufactured inexpensively, especially because complex oil introduction can be avoided by using electromechanical elements.

[0021] In the following, further embodiments of pressure sensors, sample separation devices and methods are described.

[0022] According to an exemplary embodiment, the material of the electromechanical element comprises an electroactive polymer, in particular a dielectric elastomer. The material may be one of a plurality of materials constituting the electromechanical element, or may be the only material constituting the electromechanical element. The material may consist solely of an electroactive polymer, possibly with the addition of fillers, or may contain other components. Such an embodiment may be advantageous due to the high ductility and / or free formability of such a material (for example compared to piezoelectric ceramics) which contribute to an increased sensitivity of the pressure sensor. Such a material may also have an advantageous thermal behavior, so that the resulting temperature differences and measurement deviations may be avoided.

[0023] According to an exemplary embodiment, the electromechanical element comprises an electrically insulating layer and two conductive layers, the electrically insulating layer being arranged between the conductive layers. The electrically insulating layer and / or the conductive layer may be formed in a foil-like manner. The conductive layer may be provided by applying a conductive material to the electrically insulating layer. Conductive carbon black At least one of graphite powder, silicone oil-graphite mixture, gold layer, and ion gel may be used for the conductive layer.

[0024] The configuration according to the exemplary embodiment may correspond to a capacitor. The conductive layer may be contacted by a corresponding electrical contact element, for example in order to measure the capacitance. The contact may be achieved by pins pressed into the electromechanical element and / or by a thin conductive sheet, in particular a polymer sheet, applied to the conductive layer. The contact of the two conductive layers may be made from different sides, in particular in order to reduce or avoid mutual influences. The contact element may be connected to a conductor track leading from the electromechanical element. For example, the conductor track may be achieved by conductive carbon black.

[0025] A plurality of electrically insulating layers, for example two, three, four or at least five, may be arranged between two conductive layers, each electrically insulating layer being separated from each other by a corresponding further conductive layer. The further conductive layers may also be contacted by electrical contact elements to measure the corresponding capacitance. This stacked construction contributes to increasing the sensitivity of the pressure sensor and / or expanding its measuring range. The stacked construction may correspond to a cascade of capacitors.

[0026] According to an exemplary embodiment, the material of the conductive layer comprises the material of the electrically insulating layer as a matrix material and a conductive filler in the matrix material. In this way, the conductive layer can be configured to have sufficient flexibility or elasticity while having electrical conductivity so as not to hinder the shape change behavior of the electrically insulating layer during pressure measurement. In particular, within the scope of the described embodiments, the shape change behavior of the conductive layer can correspond to the shape change behavior of the electrically insulating layer, for example in terms of elasticity. If the surface of the frame element comprises spatial structures that increase the sensitivity and / or extend the measuring range, the conductive layer must additionally have sufficient elasticity to be pressed into these spatial structures.

[0027] According to an exemplary embodiment, the matrix material is at least one of silicone and acrylic resin, and / or the conductive filler is at least one of conductive carbon black, graphite, iron oxide particles, aluminum particles, silver powder, stainless steel fibers, and carbon fibers. These materials may be particularly advantageous in terms of the shape change behavior of the electromechanical element.

[0028] According to an exemplary embodiment, the electromagnetic property is capacitance. If the electromechanical element is constructed as described above, the electromechanical element corresponds to a capacitor, whose capacitance depends on the pressure applied to the electromechanical element and the corresponding shape change. The capacitance change can be caused at least in part by the distance change between the conductive layers.

[0029] According to an exemplary embodiment, the surface of the frame element pressed against by the electromechanical element and / or the corresponding surface of the electromechanical element comprises a spatial structure which increases sensitivity and / or extends the measuring range. The corresponding surface may be the surface of the electromechanical element pressed against said surface of the frame element.

[0030] According to an exemplary embodiment, the spatial structure for improving the sensitivity and / or extending the measuring range comprises at least one cavity between the electromechanical element and the frame element, wherein the electromechanical element is pressed into the cavity as the applied pressure increases. The shape change caused by the pressure applied to the pressure sensor may include pressing into the cavity. If no pressure is applied to the electromechanical element, the cavity may have a maximum volume. The spatial structure may include a plurality of spatially separated cavities, in particular two, three, four, at least five or at least ten. The characteristic curve of the pressure sensor may be adjusted by the shape and size of one or more cavities. Along the surface of the frame element against which the electromechanical element is pressed, at least two, in particular at least three, and in particular at least five cavities may have different geometric dimensions, such as different surfaces, different depths or different diameters.

[0031] According to an exemplary embodiment, at least one cavity, in particular all cavities, are connected to the environment of the pressure sensor, for example via a channel arranged in the frame element. Thus, descriptively speaking, at least one cavity is ventilated. The environment can have an ambient pressure that does not correspond to the applied pressure to be determined. The ambient pressure can be, for example, atmospheric pressure. Such an exemplary embodiment may be advantageous in order to determine a relative pressure with respect to the ambient pressure. In contrast, if a connection to the environment is missing, an absolute pressure can be determined.

[0032] According to an exemplary embodiment, the spatial structure comprises a plurality of recesses and / or a plurality of protrusions, which are arranged in the surface of the frame element against which the electromechanical element is pressed and / or in the corresponding surface of the electromechanical element. Such recesses and / or protrusions can provide one or more cavities into which the electromechanical element moves as the applied pressure increases. The characteristic curve of the pressure sensor can be adjusted by the shape and size of the recesses and / or protrusions.

[0033] According to an exemplary embodiment, the recesses and / or protrusions are arranged concentrically. They can be arranged concentrically around the center or center of gravity of the surface of the frame element and / or the corresponding surface of the electromechanical element, wherein these surfaces can be circular. The recesses and / or protrusions can be formed in a ring shape. Adjacent recesses and / or protrusions can be at an equal distance from each other. The recesses and / or protrusions can be arranged at the center or center of gravity. In the concentric arrangement of the recesses and / or protrusions, the electromechanical element can be pressed more strongly into the central cavity under low pressure, and then pressed into the nearest outer annular cavity under higher pressure, and finally pressed into the outermost annular cavity under high pressure. In this way, an at least approximately linear characteristic curve or linear sensor characteristic of the sensor can be achieved.

[0034] According to an exemplary embodiment, two of the recesses and / or two of the protrusions include at least one of different geometric dimensions and different distances to the surface of the frame element pressed against by the electromechanical element and / or the edge of the corresponding surface of the electromechanical element. For example, they can have different depths or heights. They can have different shapes, such as circular, oval or irregular shapes. The shape can extend in the corresponding surface, or at least be parallel to it. The shape can have different surfaces, such as different diameters, wherein the diameter can be defined in the corresponding surface. Three, in particular at least five, of the recesses and / or three, in particular at least five of the protrusions can each have different geometric dimensions. The sensor characteristics or the characteristic curve of the sensor can be adjusted by such an unequal structure. In particular, linear sensor characteristics can be achieved approximately and for a defined area.

[0035] According to an exemplary embodiment, the depressions and / or protrusions form a convex structure. The convex structure may include a hump-shaped protrusion and / or a hump-shaped depression. A linear sensor characteristic may also be approximately achieved by such a convex structure.

[0036] According to an exemplary embodiment, the thickness of the electromechanical element is one to ten times, in particular one and a half times to three times, the profile depth defined by the recesses and / or protrusions. For example, the profile depth may correspond to the sum of the maximum depth of the recesses and the maximum height of the protrusions. Alternatively, the profile depth may correspond to the sum of the average depth of the recesses and the average height of the protrusions. For example, the profile depth may be 0.3 mm and the thickness of the electromechanical element may be 0.45 mm to 0.9 mm. The thickness may be defined as perpendicular to the surface of the frame element when the electromechanical element abuts against the surface of the frame element. In order to increase the influence of the profile on the sensor characteristics, such a ratio between the thickness of the electromechanical element and the profile depth may be advantageous.

[0037] According to an exemplary embodiment, the diameter of the exposed surface of the electromechanical element is less than 20 mm. The thickness of the electromechanical element can be 0.45 mm to 0.9 mm. The thickness of the optional separation element can be less than 1 mm, in particular between 0.2 mm and 0.3 mm. The profile depth can be between 0.2 mm and 0.5 mm. Accordingly, a particularly compact pressure sensor can be provided.

[0038] According to an exemplary embodiment, the electromechanical element is biased against the frame element, in particular in order to enable measurement of a negative pressure applied to the pressure sensor. The bias can act in a direction perpendicular to the surface of the frame element, wherein the applied pressure to be measured presses the electromechanical element against the surface. The bias can be present even if no pressure to be measured is applied to the pressure sensor. The operating point of the sensor characteristic can be offset by such a bias in order to enable measurement of negative pressures. The offset of the operating point can correspond to the bias. The maximum measurable negative pressure can be determined by the bias.

[0039] According to an exemplary embodiment, the bias is at least partially generated by a membrane, which is attached to the frame element and at least partially covers the electromechanical element. To this end, the electromechanical element can extend from the groove of the frame element. In other words, the side wall of the groove can be shortened compared to the electromechanical element introduced. The membrane can at least partially cover the exposed or exposed surface of the electromechanical element for pressure measurement. It can be configured to hold and / or position the electromechanical element. In addition, the membrane can be a separation element that separates the electromechanical element from the liquid or gas to be measured. The membrane can be attached to the frame element by an attachment element, which is also used as an adjustment element in particular. It can be attached by being clamped between the frame element and the base element into which the frame element is inserted.

[0040] According to an exemplary embodiment, the bias is at least partially generated by the electromechanical element being clamped into the frame element. The electromechanical element can be clamped laterally, in particular by a form fit between the side walls of the recess of the frame element and the corresponding surface of the electromechanical element. For example, for this form fit, a retaining element (such as a tooth or the like) can be attached to the side walls of the recess.

[0041] According to an exemplary embodiment, the bias is at least partially generated by a protrusion on the surface of the frame element against which the electromechanical element is pressed. Such a protrusion causes a deformation of the abutment surface of the electromechanical element, thereby determining the bias. The bias can be generated by the protrusion in combination with a membrane that holds or positions the electromechanical element.

[0042] According to an exemplary embodiment, the bias may be generated at least partially electromagnetically, for example by applying a voltage to a capacitor formed by electromechanical elements.

[0043] According to an exemplary embodiment, the pressure sensor further comprises a separation element, in particular a membrane, which covers the electromechanical element in a liquid-tight and / or airtight manner. The pressure sensor comprises a separation element. The electromechanical element can be at least partially, in particular completely, introduced into a groove of a frame element, wherein the separation element covers the groove. The material of the membrane can comprise an elastomer, in particular a perfluoroelastomer (FFKM) and / or a rubber wrapped with at least one of Teflon, silicone and fluorosilicone. Alternatively or additionally, the material of the membrane can comprise a non-elastomer, in particular at least one of steel, metal, polyetheretherketone (PEEK), fluoroethylenepropylene (FEP), polypropylene (PP) and polyethylene (PE). The separation element can be or comprise a metal foil, in particular a metal foil with a suitable coating. The separation element can protect the groove of the electromechanical element and / or the frame element from the influence of liquid and / or gas, the pressure of which will be determined by the pressure sensor. To this end, the separation element can be made of a strong and / or corrosion-resistant material.

[0044] According to an exemplary embodiment, the membrane comprises a microstructure, in particular at least one bead. This exemplary embodiment may be advantageous if the material of the membrane does not comprise an elastomer in order to ensure a low stiffness of the membrane. Thus, a microstructure, such as a bead, may also reduce the stiffness, in particular in order to make the deformation of the sensor simpler and more sensitive. However, even if the membrane comprises an elastomer, such a microstructure may also increase the sensitivity of the sensor. The microstructure may be configured to at least partially convert tensile stresses into bending stresses.

[0045] According to an exemplary embodiment, the electromechanical element is molded on the abutting surface profile of the separation element, in particular on the microstructure of the surface profile of the separation element. The electromechanical element can be molded on one or more beads in the surface profile of the separation element. To this end, the surface of the electromechanical element that abuts the surface profile of the separation element can be complementary to the surface profile shape of the separation element. Molding can be achieved by common production processes for separation elements and electromechanical elements. Molding can improve sensor quality.

[0046] According to an exemplary embodiment, the electromechanical element is adhered to the separate element by adhesive means.

[0047] According to an exemplary embodiment, the pressure sensor further includes a base member into which the frame member is inserted.

[0048] According to an exemplary embodiment, the electromechanical element is at least partially introduced into a recess of the frame element, wherein a gap is arranged between the side edge of the recess and the electromechanical element. The gap can be adjusted by means of centering elements, in particular corresponding centering elements in the frame element and the separating element. Another corresponding centering element can be arranged in a base element for the frame element to be inserted. If no pressure to be measured is applied to the electromechanical element, the gap can have a maximum extension. For example, if the electromechanical element consists of an incompressible or at least slightly compressible material, such a gap can be advantageous because a cavity is created thereby, into which the material can yield when the electromechanical element is compressed.

[0049] According to an exemplary embodiment, the other surface of the frame element against which the separation element abuts comprises a plurality of adjustment elements. The surface of the base element against which the separation element abuts likewise comprises a plurality of adjustment elements. For example, such adjustment elements may be teeth. The adjustment elements may be arranged in a tortuous manner. The adjustment elements may be configured to fix the separation element, in particular the membrane, in a stress-free and self-adjusting manner.

[0050] According to an exemplary embodiment, the separation element is divided into measuring parts.

[0051] According to an exemplary embodiment, the pressure sensor is arranged before the pumping system of the sample separation device, in particular upstream of the pumping system. The pumping system can be configured to transport a mobile phase of high pressure, in particular a pressure higher than 100 bar, in particular a pressure higher than 1000 bar, through a liquid path of the sample separation device, in particular a liquid path between the pumping system and the sample separation device. Therefore, the pressure sensor can be arranged in a low-pressure liquid path before the pumping system, in particular a liquid path with a pressure lower than 1000 bar, lower than 100 bar, lower than 10 bar. Because the pressure sensor is particularly suitable for low-pressure areas, in particular due to the material used and / or the surface structure that improves sensitivity and / or expands the measurement area, this arrangement may be advantageous.

[0052] According to an exemplary embodiment, the sample separation device may include a sample separation device for separating a sample in a mobile phase. The sample separation device may be formed as a chromatographic separation device, particularly a chromatographic separation column. In chromatographic separation, the chromatographic separation column may be equipped with an adsorption medium. At this point, the fluid sample may be retained, and only later will it be separated again in parts more slowly or in the presence of a specific solvent combination, thereby achieving separation of the sample into its components.

[0053] The sample separation device can be a microfluidic measurement device, a life science device, a liquid chromatography device, an HPLC (high performance liquid chromatography), an UHPLC device, an SFC (supercritical liquid chromatography) device, a gas chromatography device, an electrophoresis device and / or a gel electrophoresis device. However, many other applications are possible.

[0054] For example, the pumping system may be configured to deliver mobile phase through the system at pressures ranging from, for example, a few hundred bar to over 1000 bar.

[0055] The sample separation device may include a sample injector or a sampling unit for introducing the sample into the fluid separation path. Such a sample injector may include an injection needle that may be coupled to a base in the corresponding liquid path, wherein the needle may be moved out of the base to receive the sample. After the needle is reintroduced into the base, the sample may be located in the fluid path, which may be switched into the separation path of the system, for example, by switching a valve, thereby causing the sample to be introduced into the fluid separation path.

[0056] The sample separation device may include a component collector for collecting the separated components of the fluid sample. For example, this component collector may guide different components to different liquid containers. However, the analyzed sample may also be supplied to a waste container.

[0057] The sample separation device may preferably include a detector for detecting the separated components. Such a detector may generate a signal that may be observed and / or recorded and indicates the presence and quantity of the sample components in the fluid flowing through the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Other objects and many attendant advantages of the embodiments of the present invention will become apparent and more readily understood by referring to the following more detailed description of the embodiments in conjunction with the accompanying drawings. Features that are substantially or functionally the same or similar are given the same reference numerals.

[0059] Figure 1 An HPLC system according to an exemplary embodiment of the present invention is shown.

[0060] Figure 2 A three-dimensional view of a partial region of a pressure sensor according to an exemplary embodiment of the present invention is shown.

[0061] Figure 3 , Figure 5 and Figure 7 Cross-sectional views of pressure sensors having different spatial structures for improving sensitivity and / or extending measurement range according to exemplary embodiments of the present invention are respectively shown.

[0062] Figure 4 , Figure 6 and Figure 8 They are shown respectively Figure 3 , Figure 5 and Figure 7 Characteristic curve of the medium pressure sensor.

[0063] Fig. 9 A cross-sectional view of a pressure sensor having a spatial structure for improving sensitivity and / or extending a measuring range according to an exemplary embodiment of the present invention is shown.

[0064] Fig.10 , Fig.11 and Fig.12 A plan view of a surface of a frame element having different spatial structures that increase the sensitivity and / or extend the measuring range according to an exemplary embodiment of the present invention is shown in each case.

[0065] Fig.13 A cross-sectional view of a pressure sensor with a set bias according to an exemplary embodiment of the present invention is shown.

[0066] Fig.14 Shows Fig.13 Characteristic curve of the medium pressure sensor.

[0067] Fig.15 and Fig.16 A cross-sectional view of a pressure sensor according to an exemplary embodiment of the present invention is shown, wherein the bias is set by different methods.

[0068] The illustrations in the drawings are schematic. DETAILED DESCRIPTION

[0069] Before describing exemplary embodiments of the present invention in more detail with reference to the accompanying drawings, some basic considerations of the present invention, which are the basis for developing the embodiments of the present invention, will be generally described.

[0070] According to an exemplary embodiment of the present invention, a component forming a pressure sensor can be provided. The component consists of a cover (frame element), a silicone stack (electromechanical element) and a membrane (separation element) with a beaded portion for optimizing stiffness. The membrane is fixed in a self-adjusting manner by retaining teeth (adjustment element) arranged in a tortuous manner. For precise and stress-free fixation, a positioning feature (Fangfeature) (centering element) is provided in the base body (base element). If pressure is applied to the membrane side, the DES formed by the silicone stack is compressed thereby, so that the capacitance changes. In order to be able to measure higher pressures with elastic materials, a stepped structure (a spatial structure that improves sensitivity and / or extends the measurement range) is provided on the cover, and the stepped structure adjusts the voltage introduced into the silicone stack so that the measurement range is extended to a larger pressure range.

[0071] According to an exemplary embodiment of the present invention, the pressure sensor includes a structured membrane (separate element) for introducing force and the capacitive effect of an electroactive polymer (EAP). In order to increase the sensitivity, a structure is applied to the frame element, which compresses the EAP (electromechanical element) sequentially as the pressure increases after the pressure is introduced. A large measuring range is thereby ensured, and the sensor is not completely deformed when the force is initially introduced. Descriptively speaking, a progressive spring is implemented. Here, the sensor element is a stack (electromechanical element) of electroactive polymers (e.g. silicone), whose capacitance changes due to compression. Here, the membrane can be divided into a measuring part. The membrane is fixed stress-free in a permanently fixed and self-adjusting manner by a special clamping element (adjusting element). In order to ensure the freedom of movement of the membrane, a bead is attached to the membrane, which converts the load condition of tension / compression (which promotes creep) into a load condition of bending and increases elasticity.

[0072] According to an exemplary embodiment, the membrane (separation element) has a very low bending stiffness and the silicone of the electromechanical element is inherently elastic. Therefore, at small membrane diameters, the smallest pressure changes can be resolved. The silicone of the electromechanical element avoids the resulting temperature differences and measurement deviations.

[0073] According to an exemplary embodiment, a pressure sensor based on an electroactive polymer (EAP) is provided. The EAP is located in an incompressible or only very slightly compressible block (electromechanical element), such as a silicone block, and the pressure measurement is performed by a shape change of the silicone block, wherein the shape change results in a change in the distance of the EAP capacitor plates. A plurality of grooves (cavities) of different shapes can be provided, into which the silicone block can "flow" under the influence of pressure, which results in a change in the distance of the EAP capacitor plates. A plurality of different grooves can be located in the silicone block and / or in the abutment (frame element), so that the pressure sensitivity can be appropriately adjusted by the pressure distribution caused by the shape of these different grooves.

[0074] Figure 1The basic structure of HPLC system is shown, and it can be used for liquid chromatography as sample separation device 10, for example. Fluid pumping system 20 supplied with solvent by supply unit 25 drives mobile phase through sample separation device 30 (for example chromatographic column etc.) comprising stationary phase. Degasser 27 can degas solvent before solvent is supplied to fluid pumping system 20. Sample injection unit 40 is arranged between fluid pumping system 20 and sample separation device 30, so that sample liquid is introduced into fluid separation path. The stationary phase of sample separation device 30 is provided to separate the composition of sample. Detector 50 (for example, flow cell with fluorescence detection) detects the separation composition of sample, and component collecting device can be provided, for outputting the sample composition of separation into the container provided for it. Liquid can be output to waste liquid container or component collecting device 60 after passing through detector 50.

[0075] Although the liquid path between the fluid pumping system 20 and the sample separation device 30 is usually under high pressure, the sample liquid is initially introduced under normal pressure into a region of the injection unit 40 separated from the liquid path, the so-called sample loop, which then introduces the sample liquid into the liquid path under high pressure. During the connection of the sample liquid in the sample loop, which is initially under normal pressure, to the liquid path under high pressure, the content of the sample loop is brought into the system pressure of the sample separation device 10 formed as an HPLC. The control unit 70 controls the individual components 20, 25, 27, 30, 40, 50, 60, 100 of the sample separation device 10, which is formed here as a liquid chromatography sample separation device.

[0076] The pressure sensor 100 for determining the liquid pressure is arranged in the low-pressure region of the sample separation device 10 before the fluid pumping system 20. However, such a pressure sensor can also be used at other points of the sample separation device 10, in particular in the low-pressure region. However, use in the high-pressure liquid path, for example after the fluid pumping system 20, is also possible.

[0077] Figure 2 A three-dimensional cross-sectional view of a pressure sensor 100 is shown, for example, as used in Figure 1 The pressure sensor 100 includes an electromechanical element 120 configured to output an electromagnetic characteristic depending on the pressure applied to the electromechanical element 120. The applied pressure can be determined based on the electromagnetic characteristic. In this example, the electromechanical element 120 includes an electrically insulating layer 121, which is arranged between two conductive layers 122. As a result, the electromechanical element 120 corresponds to a capacitor, whose capacitor plates are formed by the conductive layers 122. In this case, the electromagnetic characteristic that depends on the applied pressure is the capacitance of the capacitor.

[0078] The pressure sensor 100 further comprises a frame element 110 having a recess into which the electromechanical element 120 is completely introduced such that an applied pressure presses the electromechanical element 120 within the recess against a surface 112 of the frame element 110. Both the frame element 110 and the electromechanical element 120 are formed cylindrically.

[0079] The separation element 130 formed as a membrane closes the recess of the frame element 110 in a liquid-tight manner, thereby protecting the electromechanical element 120 located in the recess from the corrosive effects of the sample liquid. The membrane 130 comprises a bead 131 which increases the elasticity of the membrane and accordingly improves the sensitivity of the pressure sensor 100.

[0080] The frame element is inserted into another groove of the base element 140. The base element 140 also includes a funnel-shaped groove, which exposes the surface of the membrane 130, behind which the electromechanical element 140 is arranged. The liquid or gas, whose pressure is to be determined, is located on the exposed surface of the membrane 130. The pressure of the liquid or gas acts on the electromechanical element 120 through the transmission of the membrane 130. The membrane 130 is clamped between the frame element 110 and the base element 140 at the lateral edges of the funnel-shaped groove.

[0081] The centering elements 116 formed in the frame element 110, the base element 140 and the membrane 130 enable an accurate positioning of the membrane 130 relative to the frame element 110. Since the electromechanical element is connected to the membrane 140 by adhesion, the centering elements 116 in particular enable adjustment of the gap 123 between the frame element 110 and the electromechanical element 120. Adjustment elements 117 on the frame element 110 and the base element 140 engage into the membrane 130 and ensure a self-adjusting, stress-free fixation of the membrane 130 on the groove of the frame element 110. Both the centering elements 116 and the adjustment elements 117 are formed at the lateral edges of the funnel-shaped groove in the region where the membrane 130 is clamped between the frame element 110 and the base element 140.

[0082] Figure 3 , Figure 5 and Figure 7 The sectional views of pressure sensors 100 with different spatial structures 113 that increase the sensitivity and / or extend the measuring range are respectively shown. Figure 4 , Figure 6 and Figure 8 Shows Figure 3 , Figure 5 and Figure 7 The corresponding characteristic curve of the pressure sensor in.

[0083] Figure 3 , Figure 5 and Figure 7The pressure sensor 100 is shown with a frame element 110 and an electromechanical element 120, respectively. By a pressure 150 applied to the electromechanical element 120, the electromechanical element 120 is pressed against a surface 112 of the frame element 110. The applied pressure 150 causes a change 151 in the shape of the electromechanical element 120.

[0084] The surface 112 of the frame element 110 against which the electromechanical element 120 is pressed comprises in each case a spatial structure 113 which increases the sensitivity and / or extends the measuring range and which, in the absence of a pressure 150, forms at least one cavity between the frame element 110 and the electromechanical element 120. The electromechanical element 120 is at least partially pressed into this cavity by the pressure 150. The higher the pressure 150, the greater the degree to which the electromechanical element 120 is pressed into the cavity.

[0085] exist Figure 3 In the pressure sensor 100 of FIG. 1 , the spatial structure 113 consists of a curved depression or a dome-shaped depression or a spherical cross-section-shaped depression in the surface 112 . The depression 113 extends over a larger area of ​​the surface 112 . Figure 4 In the Figure 3 1 , which shows a characteristic curve 161 of a pressure sensor in FIG. 1 , which shows a capacitance 160 of an electromechanical element as a function of a pressure 150 applied to the electromechanical element.

[0086] exist Figure 5 In the pressure sensor 100 , the spatial structure 113 is composed of two adjacently arranged curved depressions in the surface 112 . Figure 6 Shows Figure 5 150 , which reflects the capacitance 160 of the electromechanical element depending on the pressure 150 applied to the electromechanical element. The change point 152 roughly divides the characteristic curve 161 into two regions. In the first region of lower pressure, the capacitance 160 depends roughly linearly on the applied pressure 150. In the second region of higher pressure, there is also a roughly linear dependence, where the slope of the characteristic curve 161 is smaller than the slope in the first region, indicating that the sensitivity of the pressure sensor 100 in this region is lower. At the change point, the cavity formed by the spatial structure between the electromechanical element 120 and the frame element 110 is mostly filled with the electromechanical element 120.

[0087] exist Figure 7 In the pressure sensor 100 , the spatial structure 113 is composed of a plurality of dome-shaped protrusions on the surface 112 . Figure 8 Shows Figure 7 The corresponding characteristic curve of the pressure sensor in Figure 6Similar to the characteristic curve of , the change point 152 divides the characteristic curve 161 into two regions. Since a large number of hillocks are distributed on the entire surface 112, the formation of the change point is relatively large. Figure 6 15. In addition, the difference in the slope of the characteristic curve 161 in the two regions is also greater. In the lower pressure region, a linear increase is shown. In the higher pressure region, saturation 153 can be seen, where the capacitance hardly changes or no longer changes at all when the pressure increases.

[0088] Fig. 9 A cross-sectional view of a pressure sensor 100 is shown with a frame element 110 and an electromechanical element 120. By a pressure 150 applied to the electromechanical element 120, the electromechanical element 120 is pressed against a surface 112 of the frame element 110. The applied pressure 150 causes a change 151 in the shape of the electromechanical element 120.

[0089] The surface 112 of the frame element 110 against which the electromechanical element 120 is pressed comprises a spatial structure 113 which increases the sensitivity and / or extends the measuring range and which forms two cavities between the frame element 110 and the electromechanical element 120. These cavities, which are formed by the depressions in the surface 112, have different diameters. The electromechanical element 120 is at least partially pressed into the cavities by the pressure 150. At low pressures 150, the electromechanical element 120 mainly "flows" into the right cavity with the larger diameter, while only at higher pressures 150 does the electromechanical element 120 also "flow" into the left cavity with the smaller diameter. By providing cavities with different diameters, the characteristic curve of the pressure sensor can therefore be adjusted in the region of higher pressure and lower pressure.

[0090] Fig.10 , Fig.11 and Fig.12 A top view of different circular surfaces 112 of the frame element against which the electromechanical element is pressed is shown. The surfaces 112 comprise different spatial structures 113 which increase the sensitivity and / or extend the measuring range. Fig.10 , Fig.11 and Fig.12 The structures shown in may each form a depression or a protrusion on the surface 112, ie, a concave or convex shape. Fig.10 A plurality of circular structures 113 evenly distributed on the surface 112 are shown. Fig.11 A plurality of elongated structures 113 are shown, oriented in different directions and likewise evenly distributed over the surface. Fig.12 Finally, a concentrically arranged annular structure 113 is shown.

[0091] Fig.13 A cross-sectional view of a pressure sensor 100 is shown, which is similar in construction to Figure 5 Pressure sensor. Figure 5Compared to the pressure sensor 100 of FIG. 1 , a convex portion 115 protruding from the surface 112 is arranged between the two recesses 114. In the absence of externally applied pressure, the convex portion 115 leads to a bias of the electromechanical element 120. This bias can make it possible to determine a negative pressure.

[0092] Fig.14 Shows Fig.13 The corresponding characteristic curve of the pressure sensor is 161. Figure 5 Compared to the pressure sensor of FIG. 1 , the bias causes a shift in the operating point 154. At the operating point 154, no pressure 150 is applied from the outside, ie, p=0.

[0093] Fig.15 and Fig.16 A cross-sectional view of a pressure sensor 100 is shown in which the bias is set using different methods. Fig.15 In the pressure sensor of , the bias is set by clamping the electromechanical element 120 at the edge into the frame element 110 using the biasing device 155. Descriptively, the electromechanical element is like a drum under tension in the transverse direction (i.e., parallel to the surface 112) as shown by the arrow.

[0094] exist Fig.16 The pressure sensor 100, with Fig.14 Similar to the pressure sensor of the present invention, the bias of the electromechanical element 120 is set by the protrusion 115 on the surface 112 of the frame element 110. In other words, the electromechanical element 120 is biased in the axial direction, that is, perpendicular to the surface 112, by the pressure point determined by the protrusion 115. As indicated by the two arrows, the electromechanical element 120 is held by the edge of the membrane 130.

[0095] It should be noted that the term "comprising" does not exclude other elements, and "a" does not exclude a plurality. Furthermore, elements described in connection with different exemplary embodiments may be combined. It should also be noted that the reference numerals in the claims should not be interpreted as limiting the scope of protection of the claims.

[0096] Reference numerals

[0097] 10. Sample separation equipment

[0098] 20 Fluid Pumping Systems

[0099] 25 Supply Units

[0100] 27 Degasser

[0101] 30 Sample separation device

[0102] 40 Injection unit

[0103] 50 Detector

[0104] 60 Component collection device

[0105] 70 Control unit

[0106] 100 Pressure Sensor

[0107] 110 frame elements

[0108] 111 Groove

[0109] 112 Surface

[0110] 113 Spatial Structure

[0111] 114 Depression

[0112] 115 convex part

[0113] 116 Centering element

[0114] 117 Regulating element

[0115] 120 Electromechanical components

[0116] 121 Electrical insulation layer

[0117] 122 Conductive layer

[0118] 123 Gap

[0119] 130 Separation Components

[0120] 131 Bead

[0121] 140 Base element

[0122] 150 Pressure

[0123] 151 Shape Change

[0124] 152 Change Point

[0125] 153 Saturation

[0126] 154 working points

[0127] 155 Biasing device

[0128] 160 Capacitor

[0129] 161 Characteristic curve.

Claims

1. A pressure sensor (100), comprising: an electromechanical element (120) configured to change a shape of the electromechanical element according to a pressure (150) applied to the pressure sensor (100) and output an electromagnetic characteristic (160) based on the shape change (151); and A frame element (110) having a surface (112) against which the electromechanical element (120) is pressed by an applied pressure (150) to cause the shape change (151).

2. The pressure sensor (100) according to claim 1, wherein: The material of the electromechanical element (120) includes an electroactive polymer, in particular a dielectric elastomer.

3. The pressure sensor (100) according to claim 1 or 2, wherein: The electromechanical element (120) comprises an electrical insulation layer (121) and two conductive layers (122), wherein the electrical insulation layer (121) is arranged between the two conductive layers.

4. The pressure sensor (100) according to claim 3, wherein: The material of the conductive layer (122) includes the material of the electrical insulating layer (121) as a matrix material and a conductive filler in the matrix material.

5. The pressure sensor (100) according to any one of claims 1 to 4, wherein: The electromagnetic property (160) is capacitance.

6. The pressure sensor (100) according to any one of claims 1 to 5, wherein: The surface (112) of the frame element (110) against which the electromechanical element (120) is pressed and / or a corresponding surface of the electromechanical element (120) comprises a spatial structure (113) which increases sensitivity and / or extends a measuring range.

7. The pressure sensor (100) according to claim 6, wherein: The spatial structure (113) comprises at least one cavity between the electromechanical element (120) and the frame element (110), wherein the electromechanical element (120) is pressed into the cavity as the applied pressure increases.

8. The pressure sensor (100) according to claim 6 or 7, wherein: The spatial structure (113) includes a plurality of recesses (114) and / or a plurality of protrusions (115), and the plurality of recesses and / or the plurality of protrusions are arranged in the surface (112) of the frame element (110) pressed against by the electromechanical element (120) and / or the corresponding surface of the electromechanical element (120).

9. The pressure sensor (100) according to claim 8, wherein: The recess (114) and / or the protrusion (115) are arranged concentrically.

10. The pressure sensor (100) according to claim 8 or 9, wherein: Two of the recesses (114) and / or two of the protrusions (115) comprise at least one of different geometric dimensions and different distances to an edge of the surface (112) of the frame element (110).

11. The pressure sensor (100) according to any one of claims 8 to 10, wherein: The thickness of the electromechanical element (120) is one to ten times, in particular one and a half to three times, the depth of the profile defined by the recess (114) and / or the protrusion (115).

12. The pressure sensor (100) according to any one of claims 1 to 11, wherein: The electromechanical element (120) is biased against the frame element (110), in particular to enable measurement of a negative pressure applied to the pressure sensor.

13. The pressure sensor (100) according to claim 12, wherein: The bias is at least partially generated by a film (114) which is attached to the frame element (110) and at least partially covers the electromechanical element (120).

14. The pressure sensor (100) according to claim 12 or 13, wherein: The bias is at least partially generated by the electromechanical element (120) being clamped into the frame element (110).

15. The pressure sensor (100) according to any one of claims 12 to 14, wherein: The bias is at least partially produced by a projection (115) on the surface (112) of the frame element (110) against which the electromechanical element (120) is pressed.

16. The pressure sensor (100) according to any one of claims 1 to 15, further comprising a separation element (130), in particular a membrane, covering the electromechanical element (120) in a liquid-tight manner.

17. The pressure sensor (100) according to claim 16, wherein: The electromechanical element (120) is molded onto an abutting surface profile of the separation element (130), in particular onto a microstructure (131) of the surface profile.

18. The pressure sensor (100) according to any one of claims 1 to 17, wherein: The electromechanical element (120) is at least partially introduced into a groove (111) of the frame element (110), wherein a gap (123) is arranged between a side edge of the groove (111) and the electromechanical element (120).

19. A sample separation device (10) for separating a fluid sample in a mobile phase into components, wherein: The sample separation device comprises: A pressure sensor (100) according to any one of claims 1 to 18, which is used to determine the pressure of the mobile phase and / or the fluid sample, wherein the pressure sensor (100) is particularly arranged upstream of a pumping system (20) of the sample separation device (10).

20. A method for determining pressure, comprising: Providing a pressure sensor (100) having an electromechanical element and a frame element; measuring an electromagnetic property (160) of the electromechanical element (120), wherein the electromagnetic property depends on a shape change (151) of the electromechanical element (120), wherein the shape change (151) is caused by a pressure (150) applied to the pressure sensor (100) pressing the electromechanical element (120) against a surface (112) of the frame element (110); and The applied pressure (150) is detected based on the measured electromagnetic characteristic (160).

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