Sample holder for an electron microscope, system and method

Abstract

The invention relates to a sample holder for a transmission electron microscope, to a system having a sample holder and to a method for using a sample holder. A sample holder (10) for an electron microscope comprises a flow channel (12), a first wall (21) which delimits a region (14) of the flow channel (12), and an actuator (15) which is designed to move the first wall (21) in order to influence a cross section in the region (14) of the flow channel (12).

Description

[0001] Research Center Jülich GmbH

[0002] G70554WO / PT 1.3148 EP / PCT

[0003] Sample holder for an electron microscope, system and procedure

[0004] Description

[0005] The invention relates to a sample holder for an electron microscope, a system with a sample holder and a method for using a sample holder.

[0006] An electron microscope is a microscope that can image an object using electrons. This is achieved using a beam of accelerated electrons. In a transmission electron microscope (TEM), thin material samples are penetrated by a focused, high-energy electron beam. Electrons passing through the sample and / or electrons scattered by the sample are detected. The resulting scattering pattern in one or more detectors of the microscope allows for a wide range of conclusions to be drawn, for example, about the atomic structure of the sample. In the early days of electron microscopy, the imaging properties of electron microscope optics were continuously improved to correct image aberrations. For several years now, the focus has been on broadening the applications of this technique, for example, in the examination of liquid and / or gaseous samples, as well as in the microscopic investigation of chemical reactions.

[0007] An electron microscope includes a sample holder for receiving a sample. The sample holder should allow the sample to be held in a defined position relative to the electron source and / or a detector. Sample holders are known that enable the static examination of liquid samples. However, in this case, the liquid must be manually placed into the designated sample chamber, which is error-prone, complicated, and not reproducible. Furthermore, microfluidic sample holders are known that contain flow channels to allow the flow of a medium. These can be used, for example, for microscopic examinations of liquids or gases. In this case, the liquid is introduced to the sample holder from the outside to flow through it.

[0008] The aforementioned features and properties can be combined arbitrarily with the embodiments of the invention. The object of the invention is to provide an advanced sample holder, an associated system, and a method.

[0009] The problem is solved by the sample holder according to claim 1 and by the system and the method according to the dependent claims. Advantageous embodiments are specified in the subclaims.

[0010] To solve the problem, a sample holder for an electron microscope is used, comprising a flow channel, a first wall that delimits a region of the flow channel, and in particular an actuator. The actuator can be configured to move the first wall in order to influence a cross-section in the region of the flow channel.

[0011] This allows the cross-section to be adjusted to provide a suitable cross-section for a specific medium. For example, media with higher viscosity require larger flow cross-sections. Replacing the sample holder with one of a different cross-section, such as when using a more viscous liquid, is no longer necessary. A defined volumetric flow rate of the medium can be set. A particularly small or thin cross-section can be selected to enable maximum electron transparency, especially depending on the medium. Manufacturing tolerances are less critical because the cross-section can be fine-tuned afterward. Furthermore, the cross-section can also be adjusted during microscopy. This enables investigations of flowing media that were previously impossible.Furthermore, gas bubbles or blockages can be dissolved or removed, for example, by temporarily increasing the cross-section. This expands the range of applications for electron microscopy.

[0012] The sample holder is suitable for use with an electron microscope, in particular a transmission electron microscope.

[0013] The flow channel serves for the passage of a medium and / or for the placement of an additional sample. A sample, in particular comprising a solid, for example nanoparticles, can be placed in the flow channel and, if necessary, immobilized. This allows, for example, the behavior of the sample upon contact with a medium to be investigated. Alternatively, the medium itself, typically a liquid and / or a gas, can be examined as a sample. Investigation includes, in particular, electron irradiation and electron detection. A liquid within the meaning of the invention is a substantially liquid substance or a substantially liquid mixture. A dispersion with a liquid dispersion medium, for example an emulsion, a suspension, or a foam, is also a liquid within the meaning of the invention. The same applies to a gas. A gas mixture, a plasma, or an aerosol, such as...Smoke or fog is a gas within the meaning of the invention.

[0014] The flow channel is, in particular, a continuous channel through the sample holder. Typically, the sample holder includes interfaces at which a medium can be introduced into and / or out of the flow channel from the outside, for example, from a holding device. The flow channel is preferably continuous from one interface to another. The flow channel can be a single, for example, curved cavity. Alternatively, the flow channel can comprise several cavities that are connected and / or branched. One or more, for example, local barriers may be present to limit the flow, at least locally. Such a flow channel can be easily cleaned using known means, for example, by using an ultrasonic bath and / or a suitable solvent.

[0015] The cross-section is a flow cross-section for the medium. The size of the cross-section, i.e., the area of ​​the flow cross-section, and / or the shape of the cross-section can be influenced. Preferably, both the size and shape of the cross-section are influenced simultaneously. The cross-section is, in particular, a cross-section of the flow channel.

[0016] Influencing can include setting. A desired size and / or shape of the cross-section can be set. Influencing can also include changing. The size and / or shape of the cross-section can be altered. This alteration can occur immediately, i.e., within a short time, and / or over a longer period in a defined time sequence. For example, a change from a first cross-section to a different second cross-section can occur continuously or gradually.

[0017] The first wall defines the flow channel. However, this is typically not the case along the entire length of the flow channel, but only in a specific region, for example, within a defined length. It has been shown that this allows the cross-section to be influenced in a particularly simple way.

[0018] Ordinal numbers such as "first" wall, "second" membrane, etc., serve only to conceptually distinguish features. The presence of a first wall does not necessarily imply the presence of a second wall. Similarly, the presence of a second membrane does not necessarily imply the presence of a first membrane.

[0019] An actuator is a component designed to convert a signal into mechanical movement, force, and / or pressure. Specifically, the actuator is configured to selectively influence the cross-section by activation via one or more electrical signals. Multiple actuators can be present and controlled individually or collectively. The actuator can move the wall directly or indirectly. In the case of indirect movement, the actuator can, for example, move another component, which in turn moves the wall. The movement of the wall is specifically relative to another, second wall or to another part of the wall. In this way, the cross-section can be influenced particularly effectively.

[0020] In particular, the actuator is configured to perform a length change of at least 0.5 nm, typically at least 1 nm, particularly at least 10 nm, preferably at least 30 nm, particularly at least 50 nm and / or at most 1000 nm, typically at most 300 nm, preferably at most 200 nm, particularly at most 100 nm. In particular, the sample holder is designed such that the thickness of the cross-section of the flow channel in this area can be adjusted to at most 500 nm, particularly at most 300 nm, preferably at most 100 nm or 80 nm and / or at least 0 nm.

[0021] In one embodiment, the first wall is configured as a first membrane. A membrane is a very thin, planar structure made of a solid. A membrane according to the invention has a thickness that is at least 10 times smaller than its width and length. The thickness of the membrane is particularly less than 1 pm. Preferably, the membrane has a thickness of at most 100 nm. The lower limit of the membrane thickness is determined by the available materials. For example, single-atom membranes made of materials such as graphene or membranes made of 2D materials can be used. In one embodiment, the sample holder further comprises a second membrane arranged on the side of the flow channel facing away from the first membrane. The flow channel is thus bounded by the two membranes. In this way, the amount of material in the transmission zone can be minimized.

[0022] The sample holder can include a sealing element for sealing the flow channel area to the outside. A vacuum typically prevails in an electron microscope. If a section of the flow channel is bounded by a membrane, preferably by two membranes, it is advantageous to seal this section against the vacuum. Particularly when the section is located between two components of the sample holder described below, this allows for the simple creation of a region whose cross-section can be controlled. The sealing element can be, for example, an O-ring or a sealing lip, which may be vulcanized to the surface. Specifically, the sealing element is arranged around the flow channel area, the radiolucent area, and / or the membrane, particularly concentrically.Preferably, the sealing element is attached to the second component and / or is substantially arranged in a recess of the second component.

[0023] In one embodiment, the sample holder further comprises at least one inlet interface and / or one outlet interface, both fluidically connected to the flow channel. The inlet and / or outlet interfaces serve to allow the medium to flow into the sample holder from outside. The interfaces are preferably located on a holding area of ​​the sample holder, which is designed to be held by a holding device. The holding device preferably has corresponding interfaces at appropriate locations, so that the medium can be transferred accordingly.

[0024] In one embodiment, the actuator comprises a piezoelectric material. The piezoelectric material is configured to move the membrane directly or indirectly to influence its cross-section. Specifically, it has two terminals for electrically contacting the piezoelectric material. The sample holder, in particular, includes two electrical contacts through which an electrical voltage can be applied to actuate the actuator. The piezoelectric material is designed to deform when an electrical voltage is applied due to the inverse piezoelectric effect. Specifically, the piezoelectric material changes its length in at least one direction of expansion. As long as the voltage is applied, the deformation persists. However, the deformation is reversible. When the electrical voltage is removed, the piezoelectric material returns to its original shape.In this way, the cross-section in the relevant area of ​​the flow channel can be controlled particularly easily and precisely. It has been shown that the cross-section of the flow channel can be adjusted with exceptional accuracy using a piezoelectric material.

[0025] In particular, a piezoelectric ceramic is used. These materials allow for a particularly large change in length and are also readily available.

[0026] In one embodiment, the actuator is arranged between two components of the sample holder; in another embodiment, the actuator is configured to selectively influence a distance between two components of the sample holder.

[0027] A component is a part of the specimen holder. In particular, at least one of the two components is at least slightly flexible. An elastic deformation of less than 1 pm is typically sufficient for this. The actuator can be directly adjacent to one or both components. There can also be one or more intermediate layers between the actuator and a respective component. When the distance changes, one or both of the components can be elastically deformed. The change in distance can be reversible. In particular, due to the elastic properties of the adjacent components, the deformation can also disappear when the force and / or movement of the actuator that caused the deformation is removed.

[0028] A first component can be a chip that carries the first or second wall, for example, in the form of a membrane. The chip can comprise or be made of silicon, silicon nitride, and / or other vacuum-compatible and electron-beam-resistant materials. Ideally, the membrane is transparent to the electron beam. A second component can be a cover, i.e., a covering that at least partially covers the first component. The second component can comprise or be made of silicon, silicon nitride, glass, titanium, plastic, and / or other vacuum-compatible and electron-beam-resistant materials. The two components can be pressed together. One or both components can be made of glass, metal, and / or plastic. In particular, the components are vacuum-compatible.The flow channel can essentially extend within one of the components, particularly in the sections outside the channel area, for example, within the cover. The other component can then be manufactured very easily. Manufacturing a flow channel inside this component is then unnecessary. The component containing the flow channel can be replaceable, especially designed as a disposable item. This allows for replacement if thorough cleaning is not possible and / or if a component with different properties, such as a different flow cross-section, is to be used.

[0029] In the case of a transparent component, a flow channel can be produced, for example, by selective laser etching (SLE). This process allows the fabrication of fine three-dimensional structures from transparent materials such as glass or sapphire, the latter also exhibiting good thermal conductivity at low temperatures (cryogenics). Cavities such as flow channels within a body can be produced particularly advantageously in this way.

[0030] In particular, the first component and / or the second component includes a recess in which the actuator is arranged. A component may also have a substantially or completely flat contact surface for direct or indirect contact with the actuator.

[0031] In one embodiment, the sample holder has a transmission area, which is specifically designed for transmission by an electron beam. In particular, the material of the sample holder present in the transmission area has a total thickness of less than 5 pm, preferably less than 1 pm, particularly preferably less than 200 nm, typically less than 100 nm, and in some embodiments at most 60 nm. The lower limit of the total material thickness can be defined by a monatomic layer for each membrane. The total thickness can be greater than 1 nm, particularly greater than 10 nm. The electron beam therefore only needs to penetrate a small amount of the sample holder material in addition to the sample itself.

[0032] The transmission path is a largely unobstructed path through which electrons can be guided through a sample in transmission electron microscopy. Specifically, the electrons flow through the membrane, which, as a thin layer, defines the flow channel. In particular, no material is present on the side of one or more membranes opposite the flow channel. Specifically, corresponding recesses are present, for example, in the first and / or second components of the sample holder, which define the preferably straight transmission path. The walls of the recesses can be angled and / or conical to detect electrons emitted and / or re-emitted at different angles and / or to allow the sample to be examined from different angles. This can be achieved, for example, by appropriately rotating the sample holder.In particular, the transmission area extends through the entire sample holder. Specifically, the transmission area is perpendicular to the main surfaces of the sample holder.

[0033] In one embodiment, the sample holder further comprises a second wall, in particular a second membrane, which is arranged on the side of the flow channel facing away from the first wall. Specifically, the first wall and the second wall are arranged or can be arranged parallel to each other. This can result in a constant cross-section of the flow channel area. Alternatively, the first wall and the second wall can be positioned or can be positioned in a non-parallel arrangement. This can result in a tapered and / or widening cross-section of the flow channel area. The arrangement or positioning can be achieved by the actuator.

[0034] In a further embodiment, at least one section of the flow channel is spiral-shaped. This section can be arranged around and / or encompass the area. The section can have a tapered and / or widening cross-section. This design allows for the adjustment of specific flow conditions within the sample holder. A medium can thus flow towards the center of the spiral. A specially shaped spiral is not required. In particular, the spiral section of the flow channel extends at least once completely, i.e., by 360°, around the area. In one embodiment, the spiral runs in a plane.

[0035] In one embodiment, the flow channel and / or the transmission channel extends through a point inside the spiral section. In particular, the transmission channel or the flow channel extends along the direction of the electron beam inside the spiral in the viewing direction. Specifically, the transmission channel or the flow channel is located on the central axis of the spiral. This allows for particularly well-defined flow conditions. The spiral design of a section of the flow channel is also an independent teaching for solving the problem. One aspect of the invention is therefore a sample holder for an electron microscope that includes a flow channel, wherein at least one section of the flow channel is spirally shaped. All features, properties, and advantages of the sample holder described further also apply to this aspect, and vice versa.

[0036] In one embodiment, the sample holder comprises a first component and a second component. In particular, the first wall, preferably the first membrane, is arranged between the first component and the second component. Specifically, the first wall is arranged between the two components perpendicular to the direction of the electron beam. "Between the components" means that at least one straight line is present, along which material of the first component, the first membrane, and material of the second component are arranged in that order.

[0037] One or both components can be elongated and / or plate-shaped. The height is then smaller by a factor of at least 3, and in particular at least 5, than the length and / or width. In particular, the second wall, especially the second membrane, is also arranged between the first and second components.

[0038] In one embodiment, the first and second components are connected to each other by means of at least one fastening element. The fastening element serves, in particular, to directly mechanically connect the two components in such a way that separation of the two components is prevented by force-fit and / or form-fit. "Directly" means that separation is not prevented by other, external components. For example, the two components can be screwed together. It is, of course, possible that one or more intermediate layers are arranged between the components, at least in certain areas. Alternatively, the two components can be held by a third part. At least one screw can serve as the fastening element. Alternatively or additionally, at least one spring can be used. The components can be clamped together by a spring or a spring mechanism.

[0039] In one embodiment, the flow channel can be selectively closed, particularly by means of the actuator. Specifically, the actuator is configured to close the flow channel, for example, by moving the first wall, and / or the first and / or second component is configured to close the flow channel. This allows the cross-section of the flow channel to be varied over a particularly wide range. Furthermore, this enables a multitude of novel applications. For example, the flow channel can function as a valve or pump.

[0040] Another aspect of the invention is a system comprising a sample holder, particularly according to the invention, and a control device. The control device serves, in particular, to electrically control the actuator, enabling it to control the actuator in order to influence the cross-section in the flow channel. The control device is, in particular, spatially separated from the sample holder and, in particular, also from the lance, so that remote control is possible without having to intervene in the electron microscope. All features, properties, and advantages of the sample holder described above also apply, in particular, to the system, and vice versa.

[0041] Another aspect of the invention is a control device for a sample holder, particularly according to the invention. All features, properties, and advantages of the sample holder and system described above also apply to the control device, and vice versa.

[0042] Another aspect of the invention is a method for using a sample holder comprising a flow channel, a first wall that delimits a region of the flow channel, and an actuator, in particular a sample holder according to the invention. The method comprises moving the first wall by means of the actuator, in particular relative to a second wall, in order to influence a cross-section in the region of the flow channel.

[0043] In one embodiment, the cross-section is influenced while a sample in the sample holder is bombarded with an electron beam and / or while a medium flows through the flow channel. The cross-section can be influenced, for example, changed, during electron beam microscopy.

[0044] In one embodiment, a vibration is generated by repeatedly narrowing and widening the cross-section. In particular, the vibration occurs at a defined, for example, constant frequency. The actuator can be excited at the desired frequency, for example, by a control device, perhaps using a wave signal. Active fluid-mechanical manipulation of the sample and / or a medium can be performed. For example, ultrasonic excitation of a sample and / or a medium can be used. Vibrations can be generated. For example, an emulsion can be produced and / or a viscosity can be influenced. High-frequency oscillations can be used for this purpose. A pulsating flow and / or a pumping effect can be generated by repeatedly opening and closing, at least partially, the cross-section in the area.For this purpose, comparatively lower-frequency oscillations can be used, for example. In principle, frequencies from a few Hertz or below up to several hundred MHz can be generated. With a small actuator and / or when generating only near-surface acoustic waves and / or waves with only small amplitudes, frequencies of more than 10 GHz can be generated. In particular, the control unit is configured to enable one or more of the described effects.

[0045] Exemplary embodiments of the invention are explained in more detail below, also with reference to figures. Features of the exemplary embodiments can be combined individually or in multiples with the claimed subject matter, unless otherwise specified. The claimed scope of protection is not limited to the exemplary embodiments.

[0046] They show:

[0047] Figure 1: a perspective view of a lance with a sample holder,

[0048] Figure 2: an enlarged view of a sample holder, Figure 3: a cross-sectional drawing of a sample holder, Figures 4 and 5: sectional views of a sample holder, Figures 6 and 7: perspective view of part of a sample holder, and

[0049] Figure 8: a schematic representation of a system. Figure 1 shows a lance 5 with a sample holder 10 for an electron microscope, in particular for transmission electron microscopy. The lance includes a holding device 7 to which the sample holder 10 can be coupled. It should be noted that in other contexts the unit consisting of the lance 5 and the sample holder 10 is also referred to as the "sample holder". The sample holder 10 can therefore encompass the lance 5. The holding device 7 holds the sample holder 10 or the two components of the sample holder 10 and is specifically designed to guide a medium to and from the sample holder 10 and / or to supply the sample holder 10 with electricity. The sample holder 10 can encompass the holding device 7.In this case, an interface for transferring medium and / or electricity to the sample holder can be provided at a position of the holding device 7 not shown in the drawings. The holding device can be referred to as a TEM holder. The figures shown are purely illustrative examples of sample holders for TFS sample holders. It is, of course, also possible to adapt the invention for other devices, such as JEOL devices.

[0050] Figures 2 and 3 each show a sample holder 10, for example, the sample holder 10 from Figure 1, in an enlarged, semi-transparent view. The sample holder 10 comprises a holding area 11, which is coupled to the holding device 7. The holding area 11 includes several interfaces for supplying a medium and electricity from the holding device to the sample holder 10, as described in detail below with reference to Figure 6.

[0051] The sample holder 10 comprises a lower first component 25 and an upper second component 26. The first component 25 and / or the second component 26 are, for example, made of glass. The first component 25 and the second component 26 are connected to each other by means of fasteners, which are here exemplified as screws 30. Purely by way of example, the embodiment shown here also includes a lower plate of the holding device 7, which extends below the first component 25. The plate can hold the first component 25 and / or the second component 26, but is not necessary to solve the problem.

[0052] The sample holder 10 comprises a flow channel 12 arranged in the second component 26, which, by way of example, extends from an inlet interface on the holding area 11 to an area 14 located in the radiographic area 18 in the front section of the sample holder 10 and back to an outlet interface on the holding area 11. In other embodiments, different and / or additional flow channels are possible. For example, an additional flow channel can extend from an additional inlet interface on the holding area 11 to a crossing point. The crossing point can, for example, be located upstream of the radiographic area 18.

[0053] The transmission area 18 serves to irradiate a sample and / or medium under investigation with electrons. The transmission area 18 is characterized by the fact that the sample and / or the returning medium is contained within a straight radiation path using as little material as possible. This minimizes the amount of material that the electrons must pass through. To achieve this, recesses 36 are provided in both the first component 25 and the second component 26. As can be seen particularly in Figure 3, the upper second component 26 has a recess 36 with a substantially cylindrical shape, and the lower first component 25 has a pyramidal or conical recess 36.The electrons can thus penetrate the sample holder 10 perpendicular to the surfaces of the first component 25 and the second component 26. Recesses can be produced, for example, by selective etching.

[0054] The region 14 of the flow channel 12, located in the transmission area 18, is bounded by two walls 21, 22. Each of the two walls 21, 22 is designed as a membrane. This minimizes the amount of material the electrons have to pass through. A first membrane 21 is attached to the top of the first component 25. In particular, the first membrane 21 spans a passage opening in the material of the first component 25 that forms the recess 36. A second membrane 22 is attached to the bottom of the second component 26. In particular, the second membrane 22 spans a passage opening in the material of the second component 26 that forms the recess 36. In this way, the electrons only have to pass through the two membranes 21, 22 and the medium and / or sample located in the intervening region 14 of the flow channel 12.

[0055] An actuator 15 is located near region 14 of the flow channel 12, shown here by way of example around region 14. The actuator 15 is configured to selectively move the first wall 21 as needed in order to influence the cross-section of the flow channel 12 in region 14. In the embodiment shown here, the actuator 15 is arranged between the first component 25 and the second component 26 such that it can push the two components 25, 26 apart in certain areas and thus also influence the distance between the membranes arranged thereon. The actuator 15 comprises a piezoelectric material which can be subjected to an electrical voltage by means of a first conductor 31 and a second conductor 32. When an electrical voltage is applied, the thickness of the piezoelectric material changes.

[0056] If the thickness of the piezoelectric material increases, the first component 25 and the second component 26 are forced apart. This also increases the distance between the first wall 21 and the second wall 22, and the cross-section in region 14 of the flow channel 12 increases. Conversely, if the thickness of the piezoelectric material decreases, the distance between the first component 25 and the second component 26 decreases. This also reduces the distance between the two walls 21 and 22, and the cross-section in region 14 of the flow channel 12 becomes smaller. The piezoelectric material has, in particular, a thickness measured along the direction of the electron beam of more than 0.1 mm, preferably more than 0.5 mm, and / or less than 2 mm, preferably less than 1 mm.

[0057] As can be seen in Figures 2 and 3, the actuator 15 or the piezoelectric material in the example shown here is ring-shaped and extends around the area 14. The central axis of the ring shape runs along the direction of the electron beam. In Figure 3, the electron beam travels vertically parallel to the surfaces of the sample holder 10 through the recesses 36 and the area 14.

[0058] The sample holder includes a sealing element 34 in the form of an O-ring, which seals the area 14 to the outside. The O-ring 34 is located between the first component 25, i.e., the first membrane, and the second component 26, i.e., the second membrane. Specifically, the O-ring 34 is pressed against these components or membranes by means of the fastening elements or screws 30. This prevents the medium from flowing out of the flow channel 12 into the vacuum typically present in the vicinity of the sample holder 10. In the example shown here, the O-ring 34 is located radially inside the actuator 15 and / or concentrically to the actuator 15. This provides a short seal with low susceptibility to failure. Alternatively, a different sealing element, such as a specifically adapted one, can be used, which may be directly connected to the glass body.The sealing element can, in principle, have any cross-section.

[0059] Figures 4 and 5 show the sample holder in a sectional perspective view, in which the two components 25, 26 and the arrangement of the O-ring, the actuator, and the recesses 36 around the area are visible. In Figure 4, the flow channel 12 runs, in plan view, at least substantially in a straight line along the longitudinal extent of the sample holder. In Figure 5, in which the first component 25 has been omitted for better visibility, the flow channel 12, on the other hand, has a spiral section 13 and also a widening or narrowing cross-section. The area 14 of the flow channel 12, whose cross-section can be influenced, is located centrally in the spiral.

[0060] Figure 6 shows the holding area 11 for coupling the sample holder 10 to the holding device described above. The sample holder 10 has an inlet interface and an outlet interface for the medium in the holding area 11, which are in flow communication with the flow channel. In addition, the sample holder 10 has a first electrical contact 38 and a second electrical contact 39 in the holding area 11, with which the at least one actuator can be controlled. The electrical contacts 38 and 39 are each connected to an electrical conductor 31 and 32, respectively, which in turn are connected to the actuator.

[0061] Figure 7 shows an embodiment of a sample holder 10 in which the flow channel 12 has a spiral section 13. The semi-transparent illustration also makes the internal parts visible, such as the flow channel 12 and the inlet and outlet interfaces 28, 29.

[0062] As an alternative to the ring shape described above, the actuator or the piezoelectric material can have the shape of a segment of a ring extending from the center of the ring over a specific angular range between 0° and < 360°. This angular range is typically greater than 180° or 270°. In this way, a targeted increase or decrease in the cross-section of the flow channel 12 in the region 14 can be achieved. The flow channel is typically enlarged or reduced uniformly throughout the entire region 14. The walls 21, 22 are typically aligned parallel to each other when not subjected to the pressure of the medium.

[0063] If only one piezoelectric element is present, a minimal number of electrical conductors are required. Alternatively, the actuator 15 can have several piezoelectric elements distributed around the area 14, for example, in a circle or arc. Several or all of these elements can be connected together so that a change in length of all elements occurs simultaneously and / or uniformly. This allows, for example, tilting movements to be performed. If several actuators or several piezoelectric elements are present, they can also be connected individually and / or in groups such that a change in length occurs only for one or some elements, and / or that different changes in length occur for different elements and / or groups of elements. In this way, the cross-section over the area 14 can be increased or decreased differently.For example, the walls 21, 22 in region 14 can be reversibly aligned by several individually switched elements or actuators through targeted voltage application so that they describe an oblique orientation, e.g., a wedge shape. The cross-section can be adjusted, for example, to widen or narrow along the flow direction of the medium. It may be possible to generate a different wedge shape, e.g., one oriented in the opposite direction, by applying a different voltage. Thus, it may be possible to generate a narrowing cross-section, a constant cross-section, and an increasing cross-section without reversing the flow direction of the medium. For n separately controlled piezoelectric elements, typically at least n+1 electrical conductors and / or at most 2*n electrical conductors are required.

[0064] Figure 8 schematically shows a system comprising a sample holder 10 and a control unit 3. An arrow represents a data connection between the control unit 3 and the sample holder 10, which can be wired and / or wireless. Preferably, the control unit is connected to the lance 5 either wired or wirelessly, and the lance is connected to the sample holder via a cable, preferably via the holding area described above with at least two conductors. The control unit 3 is, in particular, electrically connected to several elements of the actuator and is configured to control the several elements of the actuator together and / or individually, optionally in groups. In this way, the described effects can be achieved.

[0065] The sample holder can also have two electrical contacts for electrical contact with the sample. These electrical contacts are located, in particular, within the flow channel. Specifically, two electrical leads are present, running from respective interfaces on the holding area to a corresponding electrical contact within this area. A control device can be configured to control the electrical contact with the sample, for example, selectively applying an electrical voltage and / or current to the sample and / or to a medium containing the sample via the electrical contacts.

[0066] In one embodiment, the actuator extends around the flow channel. In another embodiment, the actuator is not located within the flow channel. In yet another embodiment, the actuator extends around the transmission area. In yet another embodiment, the actuator is not located within the transmission area. In other words, the region or the transmission area can be located radially within the actuator. This allows the cross-section to be influenced while simultaneously achieving maximum electron transparency. Furthermore, the additional advantage is that the sample area remains field-free or virtually field-free when the actuator is operated at high voltages, for example, in the case of a dielectric elastomer or piezoelectric material, since the surrounding field cancels itself out at the center.

[0067] The actuator can extend around the flow channel and / or the transmission area at an angular range of 360° or less. For example, the actuator can extend around the flow channel and / or the transmission area at an angular range of at least 180°, in particular at least 200°, 220°, or 240°, preferably at least 260°, 280°, or 300°, and most preferably at least 320° or at least 340°. The actuator can be a single piece or multiple pieces. The angle is measured, in particular, around a center point of the transmission area with a viewing direction along the beam direction. The actuator can be designed in the form of a ring or part of a ring, for example, a sector of a circular ring. The actuator can be arranged in the form of a ring or part of a ring, for example, a sector of a circular ring. The actuator can be a single piece or multiple pieces.The center point of the circle, ring, or ring sector can be the center point of the transmission area. The actuator can be multi-part and arranged around the area.

[0068] The actuator can be distributed around the area. The actuator can be arranged around the area.

[0069] The actuator can comprise an electroactive polymer, such as a dielectric elastomer, and / or a fluid cushion, such as a gas cushion or a liquid cushion. An electroactive polymer is a polymer that changes its shape when an electric voltage, electric field, or electric current is applied. A dielectric elastomer is an electroactive polymer. A fluid cushion is a movable structure with at least one inlet and / or outlet for a fluid, the shape of which can be changed by adding or removing a fluid. In this way, movement can be generated to influence the cross-section.

[0070] In one embodiment, the sample holder includes a sealing element. This sealing element can serve to seal the area to the outside. This allows the area to be sealed against the environment inside the microscope, where a vacuum typically prevails. The sealing element can be circumferential and / or circular, e.g., as an O-ring. The sealing element can be located between the first component or membrane and the second component or membrane. The sealing element can be held or pressed between the aforementioned components or membranes by means of one or more fasteners, such as screws. The sealing element can be arranged radially within the actuator and / or concentrically to the actuator. This provides a short seal with low susceptibility to failure.

[0071] In particular, the sample holder includes a transmission area for irradiating a sample and / or medium under investigation with electrons using an electron beam. The flow channel area is located within this transmission area. The actuator is arranged or distributed around this area. Reference numerals: Control unit 3, Lance 5, Holding device 7, Sample holder 10, Holding area 11, Flow channel 12, Section 13, Area 14, Actuator 15, Transmission area 18, First wall 21, Second wall 22, First component 25, Second component 26, Input interface 28, Output interface 29, Screw 30, First conductor 31, Second conductor 32, O-ring 34, Recess 36, First electrical contact 38, Second electrical contact 39

Claims

Jülich Research Centre GmbH G70554WO / PT 1.3148 EP / PCT Claims 1. Sample holder (10) for an electron microscope, comprising a flow channel (12), a first wall (21) that delimits a region (14) of the flow channel (12), and an actuator (15) that is configured to move the first wall (21) to influence a cross-section in the region (14) of the flow channel (12).

2. Sample holder (10) according to the preceding claim, wherein the first wall (21) is configured as a first membrane.

3. Sample holder (10) according to the preceding claim, further comprising at least one inlet interface (28) fluidically connected to the flow channel (12) and one outlet interface (29) fluidically connected to the flow channel (12).

4. Sample holder (10) according to one of the preceding claims, wherein the actuator (15) comprises a piezoelectric material.

5. Sample holder (10) according to one of the preceding claims, wherein the actuator (15) is arranged between two components (25, 26) of the sample holder (10) and is configured to selectively influence a distance between the two components (25, 26).

6. Sample holder (10) according to one of the preceding claims, wherein the sample holder (10) has a transmission area (18) for transmission by means of an electron beam, wherein material present in the transmission area (18) in particular has a total thickness of less than 5 pm.

7. Sample holder (10) according to one of the preceding claims, wherein the sample holder (10) further comprises a second wall (22), in particular a second membrane, which is arranged on one side of the flow channel (12) facing away from the first wall (21), in particular wherein the first wall (21) and the second wall (22) are arranged parallel to each other and define a constant cross-section of the region (14) of the flow channel (12), and / or wherein the first wall (21) and the second wall (22) can be positioned in a non-parallel arrangement and define a tapered and / or widening cross-section of the region (14) of the flow channel (12).

8. Sample holder (10) according to one of the preceding claims, wherein at least one section (13) of the flow channel (12) is spiral-shaped and in particular has a tapered and / or widening cross-section.

9. Sample holder (10) according to the preceding claim, wherein the area (14) of the flow channel (12) and / or the radiographic area (18) passes through a point inside the spiral section (13).

10. Sample holder according to one of the preceding claims, wherein the sample holder has a first component (25) and a second component (26), wherein the first wall (21) is arranged between the first component (25) and the second component (26).

11. Sample holder (10) according to one of the preceding claims, wherein the area (14) of the flow channel (12) is selectively closable.

12. System comprising a sample holder (10) according to one of the preceding claims and a control device (3) for controlling the actuator (15).

13. Method for using a sample holder (10) comprising a flow channel (12), a first wall (21) which limits a region (14) of the flow channel (12), and an actuator (15), the method comprising moving the first wall (21) by means of the actuator (15) to influence a cross-section in the region (14) of the flow channel (12).

14. Method according to the preceding claim, wherein the cross-section is influenced while a sample located in the sample holder (10) is bombarded with an electron beam and / or while a medium flows through the region (14) of the flow channel (12).

15. Method according to one of the two preceding claims, wherein a vibration is generated by repeated narrowing and enlarging of the cross-section.

Images