Rotary rheometer and method for producing a component

Abstract

The invention relates to a rotary rheometer and to a method for producing a component for a rotary rheometer. A rotary rheometer (10) comprises a driven rotor (20) with a first measuring part (11) and a detection device (14) for detecting an angular position, wherein a second measuring part (12) can be arranged opposite the first measuring part (11) on a common axis (A) with the first measuring part (11), in such a way that a sample space (16) for receiving a sample (17) to be analysed is provided between the first measuring part (11) and the second measuring part (12). The rotor (20) has a moment of inertia of at most 10-6 kg*m2.

Description

[0001] Rotational rheometer and method for producing a component

[0002] Description

[0003] The invention relates to a rotational rheometer and a method for producing a component for a rotational rheometer.

[0004] Rheometers are used to investigate the flow and deformation behavior of materials. For example, complex fluids or multicomponent systems can be examined with regard to the structure, composition, type, and size of the particles they contain. Viscoelastic behavior, i.e., a combination of viscous and elastic behavior, can also be characterized in this way. Oscillation tests are particularly important because they are suitable for all viscoelastic materials. Oscillation tests involve a periodic reversal of the direction of the load.

[0005] Rotational rheometers comprise two rotationally symmetrical components, e.g. circular plates, arranged on a common axis and between which the liquid to be tested is placed.

[0006] Conventional rotational rheometers are capable of shearing a sample against a static environment by applying an applied torque. The deformation of the sample can be measured, for example, by an angle measurement. For measurement, the sample is placed on a slide and in a measuring gap of known geometry. The measuring gap can be located, for example, between two plates (plate-plate system) or between a cone and a plate (cone-plate system). For stationary or transient measurements, a movement occurs in one direction; for dynamic measurements, the applied shear stress oscillates. This allows measurements up to an oscillation frequency of 100 Hz.

[0007] In principle, a strain-controlled measurement is possible (CR rheometer, "controlled rate"), in which the measuring part on which the sample is located is rotated and the force or moment of the measuring part opposite the measuring gap, i.e. the cone or plate, is measured. A defined shear rate is specified and the resulting shear stress is determined. A shear stress-controlled or load-controlled measurement is also possible (CS rheometer; "controlled stress"), in which the measuring part located above the sample is rotated. A defined shear stress is specified and the velocity gradient, which is proportional to the viscosity, is determined. A CR measurement is also possible in which the measuring part located above the sample is rotated. In this case, the shear stress can be measured.

[0008] Conventional rotational rheometers require a sample volume of at least 50 pl in the case of a plate-plate system with a diameter of 8 mm and a plate spacing of 1 mm and at least 20 pl in the case of a cone-plate system, also with a diameter of 8 mm.

[0009] For stationary measurements, the lower torque limit is approximately 10 pNm, and for oscillatory measurements, approximately 1 pNm. For low-viscosity samples, a larger sample volume is often required to measure effectively.

[0010] It is technically complex to determine the angular position of the rotor.

[0011] In conventional rotational rheometers, a compliance correction is also applied to account for deviations between the measured angular position and the actual angular position of the sample. Large compliance corrections are particularly necessary for large rotational rheometers and / or mechanical connections that exhibit play.

[0012] Furthermore, for special applications, such as the characterization of certain polymers, so-called microrheological studies are known. In these studies, small particles are added to the sample and their behavior is microscopically determined and evaluated. The particles can be passively tracked, or their movement can be actively influenced. However, such methods are difficult to evaluate, unsuitable for complex fluids, unsuitable for larger deformations, and the viscosities that can be investigated are limited.

[0013] Furthermore, applications are known in which small samples are sheared linearly between plates. It is also known to microscopically examine complex fluids to investigate phase boundaries, bonding forces, and degrees of freedom of the individual components. The object of the invention is to provide an advanced rotational rheometer and an advanced method for manufacturing a component for a rotational rheometer. In particular, at least some of the aforementioned disadvantages are to be remedied.

[0014] This object is achieved by the rotational rheometer according to claim 1 and by the method according to the independent claim. Advantageous embodiments are specified in the subclaims.

[0015] To achieve this objective, a rotational rheometer is used, which comprises a driven rotor with a first measuring part and, in particular, a detection device for detecting an angular position. A second measuring part can be arranged opposite the first measuring part on a common axis with the first measuring part such that a sample space for accommodating a sample to be examined is provided between the first measuring part and the second measuring part. In particular, the rotor has a moment of inertia of at most 10' 6 kg*m 2 on.

[0016] The rotational rheometer according to the invention can be built very compactly. This allows for the required sample volumes to be very small. This makes it possible to examine very valuable or rare samples, as well as samples that are only present in small quantities. Examples include microorganisms in biofilms, certain blood compositions that enable microcirculation in the blood vessels of the brain, synthesized active ingredients from pharmaceutical chemistry or combinatorial chemistry, or pastes for the production of integrated circuits, which can thus be examined using particularly small volumes. Despite the small volume, a high degree of accuracy can be achieved during the examination. The rotational rheometer is particularly suitable for determining the flow and / or deformation behavior of complex fluids.Due to the compact design, the possibility of angle measurement close to the sample chamber and / or the small number of mechanical connections, only very small compliance corrections are necessary.

[0017] Due to the very low moment of inertia (or mass moment of inertia) compared to conventional rheometers, low-viscosity materials can be well characterized even with very small sample volumes. Thus, a particularly high sensitivity is achieved with respect to the shear stress. Furthermore, the low inertia of the rotating parts allows for a particularly high oscillation frequency. According to the invention, the rotational rheometer can be configured to achieve an oscillation frequency of up to 10 3 Hz, especially up to 5*10 3 and preferably up to 10 4 Hz to reach.

[0018] In other words, a miniaturized macroscopic rotational rheometer is provided. This retains the advantages of the macroscopic rheometer while significantly reducing the volume requirement.

[0019] The moment of inertia, or mass moment of inertia, describes the inertia of a rigid body relative to a change in its angular velocity when rotating around its axis. Small moments of inertia enable rapid acceleration and / or high frequencies during oscillation. The rotor's moment of inertia is preferably no more than 5*10'. 7 kg*m 2 and particularly preferably not more than 1*10 -7 kg*m 2 In a particularly preferred embodiment, the moment of inertia of the rotor is at most 5*10' 8 kg*m 2 and in one embodiment approximately 2.5*10' 8 kg*m 2 In certain embodiments, the moment of inertia of the rotor may not exceed 5*10'9 kg*m 2 or approximately 2*10' 9 kg*m 2 Typically, the moment of inertia is greater than 10' 1 ° kg*m 2 .

[0020] The lower the moment of inertia, the faster the acceleration can be and / or the higher the oscillation frequencies can be achieved. Tests have shown that with the inventive moment of inertia of a maximum of 10' 6 kg*m 2 A significant increase in acceleration and / or frequency is already possible. The further reduced moments of inertia lead to advantageously further increased accelerations and / or frequencies.

[0021] State-of-the-art rotational rheometers have a moment of inertia of approximately 10' 5 kg*m 2 and are thus an order of magnitude higher than the invention.

[0022] The first measuring part and the second measuring part together serve to shear the sample. The sample is typically placed between the two measuring parts, and the sample is sheared by rotating the first measuring part relative to the second measuring part, which typically remains stationary. For example, a force or movement of the first measuring part can then be measured in order to derive information about the flow and / or deformation behavior of the sample. In particular, the first measuring part and / or the second measuring part has a contact surface for contacting the sample.

[0023] The first measuring part can be designed, for example, as a cone or at least comprise a cone. Alternatively, the first measuring part can be designed as a flat plate. The second measuring part can be designed, for example, as a flat plate.

[0024] The sample chamber is a space in which the sample can be accommodated or arranged. The sample chamber is typically bounded by the two measuring sections.

[0025] The sample to be examined is typically placed on or inserted into the first measuring part or the second measuring part. The other measuring part is positioned in particular so that it touches the sample.

[0026] The sample can, for example, be applied to a sample carrier that can be attached to the first measuring part or the second measuring part, in particular in a rotationally fixed manner, or that is part of the first measuring part or the second measuring part. The sample can therefore be arranged directly or indirectly on one of the measuring parts.

[0027] In one embodiment, the first measuring part can be reversibly attached to and detached from the rotor in a non-destructive manner. In particular, a force-locking connection is established in at least one spatial direction, preferably a force-locking connection that prevents pull-out along the axial spatial direction. In particular, a form-locking connection is established in at least two, preferably radial, spatial directions.

[0028] The axis is typically the rotational axis of the rotational rheometer. The axis is the rotational axis of one of the measuring parts. The sample is rotated around the axis. The other measuring part is then typically also rotated around the axis.

[0029] The rotor typically forms a physical axis. The rotor is driven by a drive, which may be part of the rotational rheometer, and thus rotates around the axis. This drives the first measuring part. The rotor is a component or a unit of mechanically interconnected components that can rotate. The rotor can therefore consist of a single component or be composed of several components. The rotor typically refers to the entirety of the interconnected and jointly rotating parts of the rotational rheometer.

[0030] The axial length of the rotor is in particular less than 100 mm, preferably less than 50 mm, and particularly preferably less than 30 mm, particularly preferably less than 25 mm. The axial length is typically more than 5 mm. This allows the moment of inertia to be advantageously reduced. In rotational rheometers known from the prior art, the rotor length is usually more than 20 cm.

[0031] The detection device is particularly configured to detect an angular position of the rotor. The detection device particularly comprises a detector that is non-rotating and / or fixedly mounted in a housing of the rotational rheometer. The detection device particularly also comprises a rotating part. This is preferably arranged on the rotor. The detector and the rotating part are configured such that the detector can detect the angular position of the rotating part. In one embodiment, the detector is configured to detect a magnetic field, and the rotating part is a magnet, for example, a permanent magnet. The detector can be a Hall sensor. The magnet can be a magnet of a drive for driving the rotor. Alternatively, an optical detection device can be provided, as explained in detail below.

[0032] The rotational rheometer is, in particular, a CS rheometer. The shear stress is controlled by the (drive) torque. The shear rate can be determined using the measured rotation angle. The detection device detects the angular position and thus the rotation angle. In particular, the rotational rheometer has a control device that receives the detected angular position from the detection device and uses it to determine a shear rate.

[0033] In one embodiment, the diameter of the rotor is no greater than 50 mm, in particular no greater than 35 mm. In a preferred embodiment, the diameter is no greater than 25 mm, particularly preferably 20 mm. The diameter of the rotor is the extension of the rotor in the radial direction perpendicular to the axis. This means the maximum diameter of the rotor, i.e. the diameter measured at the thickest point of the rotor. This can be, for example, part of an axial bearing of the rotor, such as a rotor disk. In other words, the diameter of the rotor is not greater than 50 mm at any point. In this way, a low moment of inertia of the rotor can be achieved in a particularly advantageous manner. The maximum diameter of the rotor is typically no less than 2 mm. Rotor diameters of known rotational rheometers are approximately 70 mm and are thus significantly larger.

[0034] In one embodiment, the sample chamber is no larger than 100 pL, in particular no larger than 50 pL. In other words, the sample chamber is designed such that only a sample volume no larger than the specified volume can be accommodated in the sample chamber for a proper measurement. The sample chamber is not suitable for accommodating larger volumes.

[0035] In one embodiment, the sample space is no larger than 80 pL. Particularly preferably, the sample space is no larger than 25 pL. The sample space typically has a volume of at least 0.1 pL, in particular at least 0.3 pL. In one embodiment, the volume of the sample space is between 5 pL and 15 pL, for example, approximately 10 pL. In one embodiment, the volume of the sample space is between 0.3 pL and 10 pL. The diameter of the sample space can be, for example, between 5 mm and 8 mm.

[0036] In one embodiment, the rotor is supported in the axial direction and / or in the radial direction by a bearing, wherein the bearing is in particular an air bearing.

[0037] In this way, a contact-free and therefore particularly low-friction and loss-free bearing arrangement is achieved. This makes it possible to achieve a particularly low minimum torque and to measure low-viscosity samples more effectively. In particular, the air bearing is designed to achieve an air cushion of at least 1 pm and / or at most 30 pm, preferably at most 20 pm. The air cushion refers to the air-filled space between the parts rotating relative to one another. In this way, maximum precision bearing arrangement is achieved with minimal volume flow. The air bearing refers to a component or an arrangement of components that supports the rotor axially and / or radially. In particular, the air bearing is stationary during operation while the rotor rotates.

[0038] The rotor typically has one or more bearing surfaces arranged opposite one or more corresponding bearing surfaces of the air bearing. The air cushion forms between the bearing surfaces of the rotor and the bearing surfaces of the air bearing during operation. For this purpose, a gas or gas mixture, for example, air, is injected through suitable openings or nozzles in at least one of the bearing surfaces.

[0039] In particular, a bearing surface of the rotor is designed as a polished surface, preferably as a polished glass surface. The bearing surface of the rotor preferably has a shape error of at most 5 μm, particularly preferably at most 3 μm. This can apply to all bearing surfaces of the rotor. In particular, a bearing surface of the bearing is designed as a polished surface, preferably as a polished glass surface. The bearing surface of the bearing preferably has a shape error of at most 5 μm, particularly preferably at most 3 μm. This can apply to all bearing surfaces of the bearing.

[0040] In one embodiment, the air bearing is constructed in two parts, with an upper bearing part blocking upward movement of the rotor and a lower bearing part blocking downward movement of the rotor. The upper bearing part and / or the lower bearing part can also block radial movement of the rotor. In particular, one of the two bearing parts is designed to block the radial movement of the rotor. This is preferably the lower bearing part. This can also be referred to as a combination bearing. The two bearing parts of the air bearing are or can be connected to one another mechanically, in particular directly or indirectly. In this way, particularly high rigidity and particularly low deflection of the rotor are achieved.

[0041] In one embodiment, the rotational rheometer comprises a clamping device for mechanically securing several parts of the air bearing. For example, the clamping device can be designed to be axially movable. In this way, two or more parts of the air bearing can be blocked from axially moving apart. In this way, movement apart due to the air to be introduced can be prevented, thus ensuring particularly durable function of the bearing. The clamping device can comprise a threaded connection with which a movable part can be pressed against a part of the bearing.

[0042] In one embodiment, a bearing gap is adjusted by etching a portion of the rotor. In this way, material can be removed in a targeted manner to adapt the rotor to an inner diameter of the air bearing. In particular, a surface of a rotor that is blocked against radial movement is treated in this way, preferably a bearing surface.

[0043] In one embodiment, the rotor has an axial bearing section, which blocks axial movement of the rotor in the air bearing. Alternatively or additionally, the rotor has a radial bearing section, which blocks radial movement of the rotor in the air bearing. For example, the axial bearing section and the radial bearing section are designed as separate components that are mechanically connected to one another.

[0044] Due to the two-part design, the respective bearing surfaces, namely the horizontally aligned bearing surface and the peripheral surface, can be manufactured with minimal deviations or tolerances, since the respective manufacturing process can be optimally adapted to the respective function.

[0045] In one embodiment, the axial bearing section is designed as a circular disk. In one embodiment, the axial bearing section is manufactured from a wafer. In one embodiment, the radial bearing section has a circular-cylindrical basic shape. The outer diameter of the radial bearing section is typically smaller than the outer diameter of the axial bearing section, in particular by at least a factor of 2, preferably by at least a factor of 2.5 and / or by at most a factor of 8, preferably by at most a factor of 5, and particularly preferably by at most a factor of 3.5.

[0046] In one embodiment, the rotor is composed of at least two separate components that are mechanically connected to one another. Mechanically connected components of the rotor can be materially connected, for example by welding such as laser welding. In one embodiment, one of the two separate components of the rotor, preferably the radial bearing section, has openings that are designed, for example, as through-openings. In particular, the component has a plurality of openings that are preferably evenly distributed around a central axis of the component. Alternatively or additionally, the component can have a central opening. The openings are aligned in particular parallel to the rotational axis of the component and / or have a circular-cylindrical shape. In one embodiment, one or more parts of the rotor or the entire rotor can be designed as a hollow body.For example, an axle can be hollow, i.e., tubular. This can further reduce the moment of inertia.

[0047] In one embodiment, a vacuum is applied to an opening designed as a through-hole during welding to connect the two components of the rotor. This allows the distance between the components to be minimized. Preferably, the components are brought closer together to within < 2 pm. This allows for particularly effective welding, as the focus of the laser radiation used can create a secure connection.

[0048] In one embodiment, the rotor is at least partially made of a transparent material. For example, an axial bearing section of the rotor can be made of a transparent material. Additionally or alternatively, a radial bearing section of the rotor can be made of a transparent material. In one embodiment, the rotor is axially and / or radially mounted in a bearing, and the bearing is at least partially made of a transparent material. In one embodiment, the rotational rheometer has a suction device for holding a sample carrier by means of negative pressure, wherein the suction device is made of a transparent material.

[0049] In one embodiment, the rotor is made entirely of a transparent material. In one embodiment, the regions of the rotor arranged between a light source and the first measuring part are made entirely of a transparent material. In this way, light can be directed vertically onto the sample to enable high-resolution microscopic examination of the sample in the sample space. This also enables manufacturing using the SLE method, as explained further below. For example, fine structures of the rotor can be manufactured with high precision in this way. In particular, the rotor has a bearing section that includes an axial bearing section and a radial bearing section. In one embodiment, the bearing section is made entirely of a transparent material. The components of the bearing section can thus be joined together by welding.

[0050] An intake device may have intake openings and / or intake channels. These can be manufactured particularly advantageously in a transparent material using the SLE process and in particularly small dimensions, as described below. This allows for particularly advantageous intake.

[0051] A transparent material is a material that allows light to pass through. A large proportion of incoming light passes through the transparent material. The transparent material can be transparent to the human eye. The transparent material can be glass, for example, preferably quartz glass.

[0052] In one embodiment, the rotational rheometer has a suction device for holding a sample carrier using negative pressure. The suction device comprises a plurality of suction openings. In particular, the suction openings have a maximum diameter of 500 μm, in particular a maximum diameter of 350 μm. A minimum diameter of the suction openings can be 5 μm.

[0053] In particular, at least 30 suction openings are provided, preferably at least 70 suction openings, and particularly preferably at least 100 suction openings. This ensures particularly uniform suction, and the surface of the sample carrier remains particularly flat in the suction-attached and thus fixed state. Leaks are minimized, and increased holding force is achieved. In particular, no more than 500 suction openings are provided. This minimizes manufacturing costs.

[0054] In particular, the intake openings of the intake device are manufactured by means of selective laser-induced etching (SLE), as explained in detail below.

[0055] The sample carrier is an object on which the sample is arranged. The sample carrier thus defines, in particular, at least one side of the sample chamber. The sample carrier can be part of the first measuring part or the second measuring part. The sample carrier is designed, in particular, as a plate or a cylinder (Couette geometry). The sample can be applied to the sample carrier, for example, as a droplet.

[0056] In one embodiment, one measuring part is designed as a cone and the other as a plate. Using a cone and a plate as measuring parts has the advantage that the shear rate is independent of the radial distance from the axis. Furthermore, even smaller sample volumes can be examined.

[0057] In one embodiment, the rotational rheometer comprises a drive for driving the rotor. In one embodiment, the drive is configured to set the rotor in continuous rotation and / or in oscillating rotation at a frequency of more than 500 Hz, in particular more than 1000 Hz, and preferably more than 2000 Hz.

[0058] In one embodiment, the rotational rheometer comprises a drive for driving the rotor, wherein the drive comprises a Helmholtz coil and at least one magnet. A Helmholtz coil comprises two coils arranged at a distance from each other. Therefore, a Helmholtz coil is also referred to as a (Helmholtz) coil pair. The magnet can be arranged between the coils. The magnet is preferably part of the rotor. The coils are preferably stationary. Two Helmholtz coils can be present to drive the magnet in rotation.

[0059] Due to the rotor's small moment of inertia according to the invention, a drive with a comparatively low drive torque, in other words a comparatively small-sized drive, can be selected without having to accept disadvantages regarding the achievable oscillation frequency. In one embodiment, the drive torque of the rotor drive is at least 10' 10 Nm and / or maximum 10' 4 Nm.

[0060] In one embodiment, a magnet, in particular a permanent magnet, is part of the rotor and is mechanically connected to the remaining parts of the rotor. The connection can be a detachable connection, for example, a force-locking and / or positive connection. In one configuration, the rotational rheometer comprises a microscope, in particular an inverted microscope, so that a sample to be examined located in the sample chamber can be examined microscopically.

[0061] In particular, the rotational rheometer is designed so that the sample can be examined or viewed microscopically during the measurement. In the case of an inverted microscope, the sample can be viewed from below.

[0062] In one embodiment, the rotational rheometer comprises a light source, such as an LED or a fiber optic cable, for illuminating a side of the sample facing away from the microscope. Even with a transparent design of the rotor, air bearing, and / or other components of the rotational rheometer, this ensures that sufficient light passes through one or more non-transparent magnets onto the sample to provide sufficient light for microscopic observation.

[0063] In one embodiment, the rotational rheometer comprises a sample carrier for supporting the sample in the sample chamber. In particular, the sample carrier has a conduit structure through which a fluid can be supplied to the sample during the measurement.

[0064] The conduit structure can have an open or closed cross-section. For example, a closed channel can be provided for supplying a liquid. A similar conduit structure can also be provided for discharging a fluid. For example, the pH value of the sample can be changed during the measurement.

[0065] In one embodiment, the conduit structure has a diameter of at most 1000 pm, in particular at most 500 pm and / or at least 30 pm. In other words, the conduit structure is designed as a microfluidic channel.

[0066] In one embodiment, the sample carrier can be configured such that the conduit structure can be used to supply and / or remove the sample from the sample carrier. In this way, the sample can be arranged on the sample carrier when the sample carrier is located in the rotational rheometer. This configuration also constitutes a separate, independent invention. A further aspect of the invention is therefore a rotational rheometer with a sample carrier for supporting a sample to be examined, wherein the sample carrier has a conduit structure with which a fluid can be supplied to the sample during the measurement. All features, advantages, and configurations of the rotational rheometer can also apply to this aspect of the invention.

[0067] In one embodiment, the rotor has an optically recognizable structure and the detection device is configured to detect the optically recognizable structure of the rotor in order to detect the angular position of the rotor.

[0068] The detection device is therefore an optical detection device, in particular a high-resolution optical detection device. The detection device is configured to determine the angular position of the rotor based on the detected optical structure of the rotor. The optically detectable structure is typically not rotationally symmetrical. In one embodiment, the optically detectable structure has been produced by laser treatment of a transparent material. The optically detectable structure comprises, in particular, a plurality of optically detectable elements that are arranged, for example, at regular intervals and / or angular positions with respect to the axis. When using a transparent material, the optically detectable structure can be distributed across multiple levels. In this way, the number of optically detectable structural elements per angular unit, and thus the resolution of the angle measurement, can be further increased.

[0069] In one embodiment, the optically detectable structure is arranged in the region of a maximum diameter and / or on a disk of the rotor, in particular an axial bearing section of the rotor. The optically detectable structure can, for example, be arranged on or parallel to a radially aligned surface or a circumferential surface. The arrangement in the region of a maximum diameter enables particularly high resolution when determining the angle. In particular, the optically detectable structure is arranged inside the material. In other words, the optically detectable structure has no contact with the surface of the component. In this way, contamination or deterioration due to external influences acting on the surface is prevented. In one embodiment, the rotational rheometer comprises the second measuring part.This is arranged or can be arranged opposite the first measuring part on a common axis with the first measuring part in such a way that the sample space is present between the first measuring part and the second measuring part.

[0070] In one embodiment, the rotational rheometer is designed so that rheological measurements can be performed at room temperature and / or atmospheric ambient pressure. In one configuration, the rotational rheometer comprises a device for temperature-regulating the sample. In this way, the measurement can be performed at a desired temperature. The temperature-regulating device can comprise a temperature-regulating fluid flowing in one or more suitable channels. The temperature-regulating device can comprise at least one Peltier element.

[0071] A further aspect of the invention is a method for producing a component, in particular for a rotational rheometer. A transparent material is treated with laser radiation to create an optically modified structure.

[0072] In particular, the method can be used to produce a component for a rotational rheometer according to the invention. An optically altered structure is a region of the transparent material that exhibits at least one altered optical property compared to a transparent material not treated with laser radiation. The change is such that it can be perceived with a suitable instrument and, in particular, with the human eye.

[0073] In particular, only one or more parts of the transparent material are treated with laser radiation. In other words, not the entire transparent material is treated with laser radiation. This creates only a selective optically altered structure. The material is selectively modified by the laser radiation. The optically altered structure is thus located in direct proximity to a non-optically altered structure. The selective modification of the transparent material can occur on the surface and / or within the volume of the transparent material. The laser radiation is particularly designed as short-pulse laser radiation, for example as femtosecond laser radiation. The optical change can be visible with suitable measuring or detection devices and possibly also with the human eye. The feed rate of the laser radiation in relation to the transparent material can be at least 1 mm / s and / or at most 12.000 mm / s. Laser radiation can be used to optically alter very small structures quickly and precisely.

[0074] The optically modified structure can be used, for example, as a structure for optically detecting a position, such as an angular position, of a rotating part such as a rotor of a rotational rheometer. Glass, preferably quartz glass, is used as the transparent material.

[0075] In one embodiment, the optically modified structure is created on multiple levels of the component. In particular, the component is rotationally symmetrical at least in some areas, and the levels are located at different radial distances from the rotation axis. For example, two, three, four, five, or more levels can be used. In particular, the optically modified structure is produced circumferentially.

[0076] In one embodiment of the method, the transparent material is part of a rotor for a rotational rheometer. In particular, the modified structure comprises markings that can be used to determine the angular position of the rotor. The angular position can preferably be determined optically.

[0077] In one embodiment, the material having the optically altered structure is treated with an etchant so that a material of the optically altered structure is removed.

[0078] In particular, the optically altered material is specifically and selectively removed from the portion of the transparent material that is not optically altered. In this way, shapes and structures in the pm range can be produced with high precision. This process is also known as selective laser etching (SLE). It can also be referred to as inverse or subtractive 3D printing. For this to happen, the etchant must come into contact with the optically altered structure. In particular, treatment with the etchant is carried out as wet-chemical etching. For example, an etchant containing HF or KOH can be used. This allows the structurally altered material to be selectively removed.

[0079] In one embodiment, a fluid channel is produced, in particular for an air bearing or an intake device. A fluid channel for an air bearing typically serves to supply and / or discharge air to the bearing, in particular, of the rotor. A fluid channel for an intake device typically serves to fluidically connect one or more intake openings to a vacuum source.

[0080] In the following, the invention is explained in more detail with reference to figures and exemplary embodiments.

[0081] The figures show:

[0082] Figure 1: a schematic representation of a conventional rotational rheometer;

[0083] Figure 2: a schematic representation of the use of the rotational rheometer according to the invention;

[0084] Figure 3: a sectional view of a rotational rheometer according to the invention;

[0085] Figure 4: a side view of a rotor;

[0086] Figure 5: a sectional drawing of a rotor;

[0087] Figure 6: a perspective view of a suction device;

[0088] Figure 7: an exploded view of a bearing;

[0089] Figure 8: a sectional drawing of a rotational rheometer according to the invention;

[0090] Figure 9: a perspective view of another suction device;

[0091] Figure 10: a perspective view of another suction device; and

[0092] Figure 11: a schematic representation of a process for manufacturing a component.

[0093] Figure 1 schematically shows a conventional rotational rheometer 10. This comprises a rotor 20 which rotates about an axis A, and a detection device 14 with which the angular position of the rotor 20 can be determined. The rotor comprises a first measuring part 11, which is designed as a cone. The rotational rheometer 10 further comprises a second measuring part 12, which is designed as a plate. Both measuring parts 11, 12 are arranged opposite one another with respect to axis A. The measuring parts 11, 12 are spaced apart from one another. Between the measuring parts 11, 12 there is a sample chamber 16, in which a sample can be accommodated in order to conduct shear tests. The sample is then in contact with both measuring parts 11, 12. The sample can be sheared by rotating the first measuring part 11 with respect to the second measuring part 12.

[0094] The rotational rheometer further includes a drive 36 that rotates the rotor 20. The rotation is schematically represented by arrow 21.

[0095] Figure 2 shows parts of a rotational rheometer according to the invention. A lower part of the rotor 20 with the first measuring part 11 designed as a cone is shown at the top. Below this is a suction device 34, which is designed to fix a sample carrier 30, on which a sample 17 is located, to a contact surface 31 by means of negative pressure. It is schematically shown how the sample carrier 30 with the sample 36 is moved obliquely into the vicinity of the suction device 34 and then, as indicated by the vertical arrows, is moved upwards to be fixed to the suction device 34. Between the vertical dashed lines, the suction device 34 has a recess 32 in which the sample is positioned in this way. The rotor 20 and the suction device 34 can be fixedly positioned relative to one another. The second measuring part 11, i.e., the cone, is partially located in the recess 32.Different designs of the suction device 34 are shown in Figures 6, 9 and 10.

[0096] Below the sample carrier 30 is a part of a microscope 39, in particular an objective lens. This allows the sample to be examined microscopically during the measurement.

[0097] Figure 3 shows a sectional view of the rotational rheometer 10 according to the invention. It can be seen that the rotor 20 is significantly smaller than in Figure 1. The moment of inertia of the rotor 20 shown here is 2.5*10' 8 kg*m 2 The rotor 20 itself is described in detail in Figures 4 and 5. The rotor 20 is mounted in a bearing 18, which is designed as an air bearing 19. This is described in detail in Figures 7 and 8.

[0098] The drive 36 for the rotor 34 of the rotational rheometer 10 comprises a Helmholtz coil 38, in which the two individual coils are vertically aligned and arranged in the housing of the rotational rheometer 10, and a magnet 37 located between the individual coils, in particular a permanent magnet, which is set in rotation by the Helmholtz coil. The magnet 37 is part of the rotor 20.

[0099] Measurement is performed using the CS (controlled stress) concept. Here, the rotor torque is specified, for example, via the coil current. The magnet and the magnetic field are known. The rotation angle and / or angular position of the rotor are measured using a detection device (not shown). The detection device can, for example, comprise two Hall sensors arranged 90° apart or be an optical detection device. The rotation angle and / or angular position can also be used for the control and / or commutation of the drive.

[0100] The rotational rheometer 10 comprises a clamping device 40 with which the different parts of the air bearing 19, for example, the upper bearing part 27 and the lower bearing part 28 according to Figure 7, are clamped or fixed relative to one another. In this way, they are held securely in position, even if excess pressure is applied in the air bearing 19 for support. The clamping device 40 comprises a threaded part 45 that can be moved vertically relative to the housing.

[0101] The rotor 10 comprises, as can be seen particularly in Figures 4 and 5, an axial bearing section 22 and a radial bearing section 23. The axial bearing section 22 serves to block an axial movement of the rotor 10. The axial bearing section 22 is designed as a circular disk and has a diameter of approximately 18.2 mm and a thickness of approximately 1 mm. In particular, directly below the axial bearing section 22 is the radial bearing section 23, which blocks radial movements of the rotor 10. The radial bearing section 23 has a circular-cylindrical basic shape, a diameter of approximately 6 mm, and a thickness of approximately 5 mm. As shown in Figure 5, the radial bearing section 23 has openings 24 in the form of through-holes. These have a circular-cylindrical basic shape and run parallel to the axis A.

[0102] In the upper area of ​​the rotor 10, a magnet 37 is arranged, which is driven by coils located in the housing of the rotational rheometer (see Fig. 3) in order to set the rotor 10 in rotation. In the lower area of ​​the rotor 10, a cone is arranged as the first measuring part 11. During operation, a second measuring part is arranged below it, as shown in Fig. 1, to define the sample space. The very low moment of inertia of the rotor 10 can be achieved, for example, by an overall small size, by a low mass and, in particular, by a small mass that is located away from the axis. Recesses can also be arranged. The maximum radial extent or the diameter of the rotor 10 at the thickest point is between 16 mm and 20 mm, e.g., approx. 18.2 mm. The radial extent of the rotor 10 is between 15 mm and 20 mm, e.g., approx. 17 mm.However, deviating from this example, larger sizes are also possible in order to achieve the object of the invention.

[0103] Figure 6 shows the first measuring part 11, in particular the cone, in a perspective view from below. An approximately annular suction device 34 with a plurality of suction openings 35 is arranged around the first measuring part. The suction device 24 has a vacuum connection 33 for applying a negative pressure. The negative pressure is applied to the suction openings 35 via flow channels, so that the second measuring part is sucked onto the particularly flat contact surface 31 of the suction device 34 and thus fixed (see Fig. 2).

[0104] Figure 7 shows the air bearing 19, in which the bearing section 29 of the rotor is mounted. The air bearing 19 comprises an upper bearing part 27 and a lower bearing part 28. The lower bearing part 28 serves as a combination bearing and supports the radial bearing section 23 and the axial bearing section 22 from below. The upper bearing part 27 supports the axial bearing section 22 from above.

[0105] Figure 8 shows details of one embodiment of the air bearing in section. The axial bearing section 22 and the radial bearing section 23 are shown in the center and are mounted in respective parts of the air bearing, for example as in Figure 7. To the right of axis A, the air inflow for the air bearing is shown. Compressed air is provided via an annular, circumferentially encircling distribution channel 41, for example at a pressure between 2 bar and 4 bar. Radially extending upper and lower supply air channels 42 branch off from the distribution channel 41. The supply air channels 42 are arranged in a distributed manner in the circumferential direction. For example, there are four supply air channels 42, each offset by 90° with respect to axis A. From the upper supply air channels 42, air is directed downwards towards the axial bearing section 22 via one or more nozzles. From the lower supply air channels 42, air is directed upwards towards the axial bearing section 22 via one or more nozzles.The air forms an air cushion between the axial bearing section 22 and the rotor and flows both radially inward and outward. In addition, air is directed radially inward from the lower air supply ducts 42 via one or more nozzles toward the radial bearing section 23. The air forms an air cushion between the radial bearing section 23 and the rotor and flows both axially upward and downward.

[0106] To the left of axis A, the air flow is shown. The air is guided radially outward via radially distributed exhaust air ducts 43. For example, there are eight exhaust air ducts 43, each offset by 45° relative to axis A. The exhaust air ducts 43 are arranged alternately with the supply air ducts 42. For example, two exhaust air ducts 43 are arranged between each supply air duct 42. The air flows from the exhaust air ducts 43 into a radially circumferential collecting duct 44 and is discharged from there.

[0107] Furthermore, Figure 8 shows that the axial bearing section 22 has schematically illustrated optically detectable structures 25. These serve to determine the angular position of the rotor and are located particularly inside the material of the axial bearing section. A corresponding detection device is arranged on the rotational rheometer, for example, on its housing.

[0108] Figure 9 shows an embodiment of a suction device 34 made of a transparent material. The suction device 34 comprises a vacuum connection 33 and a contact surface 31 with a plurality of suction openings 35 that are in fluid communication with the vacuum connection 33. For example, 120 suction openings 35 are provided. The suction openings 35 have a circular cross-section and a diameter of, for example, 300 μm. The suction openings 35 are preferably produced using selective laser-induced etching. The large number of very small suction openings 35 achieves particularly uniform, flat suction.

[0109] Figure 10 shows another embodiment of a suction device 34. This is fundamentally similar in shape to the suction opening shown in Figure 9. However, instead of the multitude of circular or point-shaped suction openings, there is a single, annular suction opening 35. This provides a suction device 24 that is easy to manufacture. Figure 11 schematically shows a method. Treatment with laser radiation 50 is carried out. A transparent material is treated with laser radiation to create an optically modified structure. Optionally, treatment with an etchant 52 is then carried out. The optically modified structure is selectively removed by an etchant.

[0110] List of reference symbols

[0111] Rotational Rheometer 10

[0112] First measuring part 11

[0113] Second measuring part 12

[0114] Detection device 14

[0115] Axis A

[0116] Rehearsal Room 16

[0117] Sample 17

[0118] Camp 18

[0119] Air bearing 19

[0120] Rotor 20

[0121] Arrow 21

[0122] Diameter D

[0123] Thrust bearing section 22

[0124] Radial bearing section 23

[0125] Opening 24 visually recognizable structure 25 upper bearing part 27 lower bearing part 28

[0126] Camp section 29

[0127] Sample carrier 30

[0128] Investment area 31

[0129] Recess 32

[0130] Vacuum connection 33

[0131] Intake device 34

[0132] Intake opening 35

[0133] Drive 36

[0134] Magnet 37

[0135] Helmholtz coil 38

[0136] Microscope 39

[0137] Bracing device 40

[0138] Distribution channel 41

[0139] Supply air duct 42

[0140] Exhaust duct 43

[0141] Collective channel 44

[0142] Movable part 45

[0143] Treatment with laser radiation 50

[0144] Treatment with etching agent 52 The rotor refers to a unit of interconnected parts that rotate together. The rotor particularly comprises a rotating part of the drive, e.g., a magnet. The moment of inertia of the rotor is composed of the moments of inertia of the individual parts of the rotor, for example, in addition to the rotating part of the drive, the first measuring part, and a shaft that connects the rotating part of the drive to the first measuring part.

[0145] In conventional rotational rheometers such as the commercially available “Thermo Scientific HAAKE RheoStress 6000”, the moment of inertia of the motor or drive alone, which constitutes only a part of the rotor, is 10 pkgm 2, i.e. 10 * 10' 6 kgm 2 and is thus ten times higher than the inventive moment of inertia of the entire rotor. The rotor can be divided into the motor or drive of the rotor and the measuring geometry of the rotor (referred to here as the first measuring part).

[0146] In one embodiment, the rotor comprises the following parts:

[0147] A magnet, which can be a rotating part of the drive and / or a detection device,

[0148] - a magnetic holder for the magnet,

[0149] - a rotor disc as part of a rotor thrust bearing (also called thrust bearing section),

[0150] - a rotor cylinder (also called a shaft) connecting the first measuring part to the rotating part or to the rotor disc (see, for example, the cylindrical part between reference numerals 23 and 11 in Fig. 4), and

[0151] - the first measuring part.

[0152] The moment of inertia of the entire rotor can be calculated as the sum of the five parts mentioned. The moment of inertia of the motor or rotor drive can be calculated as the sum of the moments of inertia of the magnet, magnet holder, and rotor disk. This moment of inertia can be a maximum of 5*10' 7 kg*m 2 , especially 10' 7 kg*m 2 , preferably no more than 5*10' 8 kg*m 2 The rotor is therefore composed of the aforementioned motor or rotor drive, the rotor cylinder, and the first measuring part.

[0153] The magnet can have a moment of inertia of maximum 10' 9 kg*m 2 , preferably no more than 10' 1 ° kg*m 2 The magnet may comprise or consist of NdFeB. The magnet holder may have a moment of inertia of not more than 10' 9 kg*m 2 , preferably no more than 10' 1 ° kg*m 2 or a maximum of 5*10' 11 kg*m2 The magnet holder can be made of light metal such as aluminum. The rotor disc, the rotor cylinder, and / or the first measuring part can be made of glass. The rotor disc can have a moment of inertia of no more than 5*10' 7 kg*m 2 , especially 10' 7 kg*m 2 , preferably no more than 5*10' 8 kg*m 2 The rotor cylinder can have a moment of inertia of maximum 5*10' 8 kg*m 2 , especially 10' 8 kg*m 2 , preferably no more than 5*10' 9 kg*m 2 The first measuring part can have a moment of inertia of not more than 10' 8 kg*m 2 , in particular no more than 10' 9 kg*m 2 , preferably no more than 8*10' 1 ° kg*m 2 In one embodiment, the moment of inertia of the rotor is at least 10' 15 kg*m 2 .

[0154] Moments of inertia can also be expressed in the unit pNms2 be specified. 1 pNms 2 corresponds to 10' 6 N*m*s 2 or 10' 6 kg*m 2 . The rotor therefore preferably has a moment of inertia of at most 1 pNms 2 .

Claims

Claims 1. Rotational rheometer (10), comprising a driven rotor (20) with a first measuring part (11) and a detection device (14) for detecting an angular position, wherein a second measuring part (12) can be arranged opposite the first measuring part (11) on a common axis (A) with the first measuring part (11) in such a way that a sample space (16) for receiving a sample (17) to be examined is present between the first measuring part (11) and the second measuring part (12), characterized in that the rotor (20) has a moment of inertia of at most 10' 6 kg*m 2 has.

2. Rotational rheometer (10) according to the preceding claim, characterized in that a diameter (D) of the rotor (20) is not greater than 50 mm, in particular not greater than 35 mm.

3. Rotational rheometer (10) according to one of the preceding claims, characterized in that the sample space (16) is not larger than 100 pL, in particular not larger than 50 pL.

4. Rotational rheometer (10) according to one of the preceding claims, characterized in that the rotor (20) is mounted in the axial direction and in the radial direction by an air bearing (19).

5. Rotational rheometer (10) according to the preceding claim, characterized in that the rotor (20) has an axial bearing section (22) which blocks an axial movement of the rotor (20) in the air bearing (19), and a radial bearing section (23) which blocks a radial movement of the rotor (20) in the air bearing (19), wherein the axial bearing section (22) and the radial bearing section (23) are designed as separate components which are mechanically connected to one another.

6. Rotational rheometer (10) according to one of the preceding claims, characterized in that - the rotor (20) is at least partially made of a transparent material and / or that - the rotor (20) is mounted axially and / or radially in a bearing (18), wherein the bearing (18) is at least partially made of a transparent material, and / or that - the rotational rheometer (10) has a suction device (34) for holding a sample carrier (30) by means of negative pressure, wherein the suction device (34) is made of a transparent material.

7. Rotational rheometer (10) according to one of the preceding claims, characterized in that the rotational rheometer (10) has a suction device (34) for holding a sample carrier (30) by means of negative pressure, wherein the suction device (34) comprises a plurality of suction openings (35) with a diameter of maximum 500 pm, in particular maximum 350 pm.

8. Rotational rheometer (10) according to one of the preceding claims, characterized in that the rotational rheometer (10) comprises a drive (36) for driving the rotor (20), wherein the drive (36) is designed to set the rotor (20) into a continuous rotation and / or into an oscillating rotation with a frequency of more than 500 Hz, in particular more than 1000 Hz and preferably more than 2000 Hz.

9. Rotational rheometer (10) according to the preceding claim, characterized in that the drive (36) comprises a Helmholtz coil (38) and a magnet (37), wherein the magnet (37) is part of the rotor (20).

10. Rotational rheometer (10) according to one of the preceding claims, characterized in that the rotational rheometer (10) comprises a microscope (39), in particular an inverted microscope (39), so that a sample (17) to be examined located in the sample chamber (16) can be examined microscopically.

11. Rotational rheometer (10) according to one of the preceding claims, characterized in that the rotational rheometer (10) has a sample carrier (30) for carrying the sample (17) in the sample space (16), wherein the sample carrier (30) has a conduit structure with which a fluid can be supplied to the sample (17) during the measurement.

12. Rotational rheometer (10) according to one of the preceding claims, characterized in that the rotor (20) has an optically recognizable structure (25) and the detection device (14) is designed to detect the optically recognizable structure (25) of the rotor (20) in order to detect the angular position of the rotor (20).

13. A method for producing a component for a rotational rheometer (10), wherein a transparent material is treated with laser radiation so that an optically modified structure is created.

14. Method according to the preceding claim, characterized in that the transparent material is part of a rotor (20) for a rotational rheometer (10), wherein the modified structure comprises markings with which an angular position of the rotor (20) can be determined.

15. Method according to one of the preceding two claims, characterized in that the material having the optically altered structure is treated with an etchant so that a material of the optically altered structure is removed.

16. Method according to the preceding claim, characterized in that a fluid channel is produced, in particular for an air bearing (19) or a suction device (34).

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