Patent Description:
Cryo-microscopy in the meaning of the present application particularly includes cryo-light microscopy and cryo-electron microscopy. Samples to be examined by cryo-microscopy are mostly prepared beforehand by a method called cryofixation. In this method, a water-containing sample is frozen very quickly (cryofixed) to a temperature of less than - <NUM>° C, i.e. it is cooled very rapidly in order to avoid the formation of ice crystals. Cryofixation has proven to be particularly suitable for investigations of structural biology. The objects to be investigated, for examples cells, enzymes, viruses, or lipid layers, thereby become embedded in a thin, vitrified ice layer. The great advantage of cryofixation is that the biological structures can be obtained in their natural state. For example, a biological process can be halted at any point in time by cryofixation, and investigated in that vitrified state, for example in a cryo-electron microscope but also in a light microscope with corresponding sample cooling. In this context, cryo-light microscopy serves principally to locate relevant regions of the sample (regions of interest), which can be noted and then relocalised and viewed in more detail in a cryo-electron microscope.

In order not to impair the quality of the frozen samples, it is advantageous that they be transferred in cooled and contamination-free, particularly water-free, fashion between the processing units being used, for example a cryofixation device, a freeze fracture apparatus, and a coating apparatus, and the analytical devices, in this case principally a cryo-light microscope and a cryo-electron microscope. Sample transfer devices, such as disclosed in <CIT>, can be used to transfer a sample under cryogenic conditions between said processing units and/or analysing units. <CIT> discloses a manipulation container for cryomicroscopy. The manipulation container comprises a holder with two clip elements and a spring-loaded plunger for fixing a sample carrier mount. A push rod and a gripper are guided through a first tube at one end of the manipulation container. The gripper grasps the sample carrier mount and is slid out of the manipulation container through a second tube at an opposite end of the manipulation container so that the sample carrier mount can be deposited in a sample stage.

Cryofixation as discussed above may be done on the sample carried by the sample carrier/grid. The grids typically comprise a metal mesh or metal grid (e.g. made of copper or gold) and a support film (e.g. a carbon web). After placing the samples on the grids, samples are cryofixed. Such grids also sometimes referred to as "baregrids". For ease of handling, the thin grids may be clamped into special metal frames. The combined structure of sample grid and metal frame is also known as "autogrid". It is noted that also other kinds of sample carriers, also in the field of cryo-microscopy, are in use.

In a next step, the sample carrier carrying the vitrified sample is loaded into a sample holder, also known as "cartridge". In the example discussed above, one or more grids are placed onto or loaded into the sample holder/cartridge. The grids are mostly loaded into the cartridge in an atmosphere of cold vaporized liquid nitrogen in the inside of a sample holder transfer device, also known as "shuttle".

A sample holder configured to receive a sample carrier/grid carrying a vitrified sample is disclosed in <CIT>. The sample holder comprises sample carrier fixing means for clamping a sample carrier between a leaf spring biased towards the intended position of the sample carrier, and an edge at the contact surface of the sample holder, at the opposite side of the leaf spring. In order to load a sample carrier into such a sample holder, the sample carrier grabbed by a pair of tweezers is pressed with its opposite side against the leaf spring such that the leaf spring allows placing the sample carrier onto the contact surface of the sample holder. The shuttle may then be connected to a cryo-microscope and the sample holder/cartridge carrying the sample carrier is transferred into the cryo-microscope for examination.

Document <CIT> relates to a cryotransfer holder and a workstation. The cryotransfer holder comprises clamps to hold down a sample carrier and the cryotransfer holder can be received in the workstation in a sample transfer space. The workstation comprises a screw, which can be rotated in order to raise away and/or lower the clamps.

An object of the present invention is to provide an improved sample holder transfer device.

This object is solved by a sample holder transfer device according to claim <NUM>. With such a sample holder transfer device it is no longer necessary to directly operate the sample carrier fixing element e.g. manually, e.g. by a pair of tweezers, in order to either "open the sample carrier fixing element", i.e. moving the at least one section of the sample carrier fixing element to its second position, or "close the sample carrier fixing element", i.e. moving the at least one section of the sample carrier fixing element to the first position. The process of opening and closing the sample carrier fixing element can now be performed via the sample holder transfer device itself, more particularly via its switching mechanism. Thus, the process of opening the sample carrier fixing member does no longer depend on the hitherto manual process of inserting the sample carrier(s).

A sample holder transfer device according to an embodiment of the present invention thus provides the opportunity of a simplified process of inserting and removing a sample carrier like a sample grid into and from a sample holder like a cartridge used in cryomicroscopy, respectively.

More particularly, a workflow in cryo-microscopy may be facilitated, as it is, for instance, no longer necessary to first insert a sample carrier/grid into the sample holder/cartridge, and in a second step to insert the sample holder/cartridge into a sample holder transfer device. In contrast, the sample holder may first be inserted into a sample holder transfer device according to an embodiment of the present invention, and the process of inserting and removing of sample carriers/grids can easily be performed by operating the switching mechanism of the sample holder transfer device accordingly.

The switching mechanism provided in an embodiment of the present invention is further configured to fix the sample holder in a loading position, when the switching mechanism is operated to switch the at least one section of the sample carrier fixing element to its second position such that a sample carrier can be inserted into or removed from the sample holder. Fixing the sample holder in a loading position while inserting or removing a sample carrier facilitates the handling process.

The switching mechanism is configured to be set into a first position, in which the switching mechanism switches the at least one section of the sample carrier fixing element into its first position ("closed" position), and the switching mechanism is configured to be set into a second position, in which the switching mechanism switches the at least one section of the sample carrier fixing element into its second position ("open" position).

Generally, and particularly also in this embodiment, an "operation of the switching mechanism" may consist of or comprise at least one of a pushing, a pressing, a pivoting, a rotary, a pulling and a touching operation. By means of such an operation of the switching mechanism, the sample carrier fixing element is switched - as defined above - from an open position to a closed position or vice versa.

The "switching mechanism" can consist of or comprise at least one of the following elements: an essentially rigid element being configured to have the function of a lever or being formed as a lever, said lever being pivotable around an axis such that actuating (e.g. pressing or pulling) one end of the lever leads to a corresponding movement of the other end of the lever, which - directly or indirectly - switches the sample carrier fixing element - as defined above - from one position (open/closed) to another (closed/open); an essentially resilient element, the resilient element preferably being biased to a position, in which the sample carrier fixing element is in a closed position, such that a actuating force onto the resilient element would result in the sample carrier fixing element switching into its open position. Another element may be a slide element or a slider, which can be moved into a position in order to act upon the sample carrier fixing element to switch it from one position into another. Yet another element may be a cam element having a cam surface, which - directly or indirectly - is in contact with the sample carrier fixing element and, depending on the point of contact at the cam surface, switches the sample carrier fixing element from one position to another. Still another element may also be a touch button, which is touched in order to cause the sample carrier fixing element to switch from one position into another. It should be noted that also a combination of the aforementioned elements may be suitable to implement a switching mechanism according to embodiments of the present invention.

It should be noted that the switching mechanism of the sample holder transfer device may act directly upon the at least one section of the sample carrier fixing element However, according to other embodiments of the present invention, the switching mechanism of the sample holder transfer device may act upon another section of the sample carrier fixing element, which section is in operative connection to the other section that is fixing or releasing the sample carrier. Corresponding embodiments will be discussed further below.

In an embodiment, the switching mechanism comprises a slide element or a cam element, the slide element or cam element being configured to - directly or indirectly - interact with the at least one section of the sample carrier fixing element in order to, upon operation of the switching mechanism (<NUM>), switch the at least one section of the sample carrier fixing element into its first (closed) position and/or into its second (open) position. In this embodiment, the slide element or cam element can either act directly upon said at least one section of the sample carrier fixing element or onto another section of the sample carrier fixing element, which section is operatively coupled with the other section for fixing or releasing the sample carrier. Further, in this embodiment, the switching mechanism may be configured to directly move the slide element or the cam element in order to act upon the sample carrier fixing element; it is, however, also possible and, in some embodiments, also preferred if the slide element or the cam element indirectly act upon the sample carrier fixing element as will be explained further below.

In an embodiment where the switching mechanism comprises a slide element (slider) or a cam element, the switching mechanism may further comprise an intermediate element, the slide element or cam element being configured to act upon the intermediate element. The intermediate element may be a resilient element or a rigid element or a combination of both, the intermediate element being operated by the slide element or cam element in order to act upon the sample carrier fixing element to switch - as defined above - from one position into another.

In an embodiment, the intermediate element comprises a spring element. The spring element might be a leaf spring. One end of the spring element may be configured to act upon the sample carrier fixing element Again, it may act directly onto the at least one section of the sample carrier fixing member configured to fix or to release the sample carrier, or it may act upon another section operatively coupled to the section configured to fix or release the sample carrier.

In another embodiment where the switching mechanism is configured to be set into a first position and into a second position, said positions corresponding to the open position and the closed position of the sample carrier fixing element, respectively, the switching mechanism may comprise a pin, the pin being rotatably mounted in the sample holder transfer device and being rotatable about its longitudinal axis and being configured to assume, by rotation about a predetermined angular range, two positions corresponding to the first position and the second position of the switching mechanism. This embodiment facilitates handling of the switching mechanism in that the pin may be configured to be operated by a tool like a screwdriver for rotating the pin about its longitudinal axis. Furthermore, this embodiment allows a reliable and robust configuration of this part of the switching mechanism. In this embodiment, the pin may further comprise the above-mentioned cam (or slide) element. In this embodiment, rotation of the pin leads to a corresponding movement e.g. of the cam surface of the cam element, which cam surface - directly or indirectly - acts upon the sample carrier fixing element in order to switch it from one position into another.

In this embodiment, the switching mechanism may comprise the pin comprising the cam element, which, in a first position of the pin exerts no force or a force less than a predetermined threshold force onto the spring element, and which pin upon rotation about the predetermined angular range assumes its second position, in which the cam element exerts a force equal to or exceeding the threshold force onto the spring element. In this embodiment, if a force exceeding a threshold force acts upon the spring element, the spring element is moved into a position where it switches the sample carrier fixing element - as defined above - from one position into another. The spring element may be biased towards a position where it does not act upon the sample carrier fixing element, such that, when a force exceeding the threshold force acts upon the spring element, the spring element switches the sample carrier fixing element into another position. Preferably, the sample carrier fixing element is biased towards the closed position. In this case, exerting a force exceeding the threshold force onto the spring element would lead to the sample carrier fixing element switching into its open position.

Further embodiments of the present invention relate to a sample holder transfer device according to the embodiments discussed above, which sample holder transfer device includes the sample holder configured for holding a sample carrier.

In embodiments where the sample holder transfer device includes the sample holder, the sample holder may comprise a sample carrier fixing element, at least one section of the sample carrier fixing element forming a first section configured, when in a first position, to fix the sample carrier to the sample holder, and, when in a second position, to release the sample carrier or to provide access to an area where the sample carrier is to be placed; the sample carrier fixing element, in this embodiment, further comprises a second section, the second section being operable by the switching mechanism of the sample holder transfer device such that upon operation of the second section the first section switches from the first into the second position or from the second into the first position.

As the sample carrier fixing element, in this embodiment, comprises two sections, namely a first and a second section, the second section can be operated in order to switch the first section into a position where it either fixes or releases the sample carrier. Thus, operation of the sample carrier fixing element is decoupled from its function to either fix or release the sample carrier. In other words, it is no longer necessary to press the sample carrier fixing element with the sample carrier itself into a position where the sample carrier can be placed onto the corresponding contact surface provided in the sample holder. In contrast, a different section of the sample carrier fixing element can now be operated to switch the first (fixing) section into its open (second) position in order to be able to properly locate and orientate the sample carrier. In a next step, the first section may either automatically or by itself return or move into the first (fixing) position, or the first section switches into this first position upon (another) operation of the second section of the sample carrier fixing element.

The sample carrier fixing element provided in an embodiment of the present invention may consist of or comprise a spring element or a resilient element or an elastic element but also a rigid element, which itself is fixed to the body of the sample holder or is an integral part of the sample holder. Alternatively or additionally, the sample carrier fixing element, particularly its first section, may consist of or comprise a clamp or a clip, either being fixed to the body of the sample holder or being an integral element of the sample holder, for securing the sample carrier. Further, it is conceivable to implement the second section of the sample carrier fixing element in the form of a push button, rotary button, resilient switch, snap switch or the like.

The sample carrier fixing element may comprise an essentially rigid element being configured to have the function of a lever or being formed as a lever, said lever being pivotable around an axis between the first and second sections such that the first section moves or pivots when the second section is moved or pivoted.

In an embodiment, the sample carrier fixing element comprises an essentially resilient element having a first section and a second section, said sections, in an embodiment, being at opposite ends of the resilient element, the resilient element being configured (in a lever-like fashion) such that the first section moves or pivots when the second section is moved or pivoted. The first section of the sample carrier fixing element may be in the form of a (retaining) leaf spring biased towards the designated area or position of the sample carrier, and the second section may be in the form of another leaf spring (or another resilient part) in connection with the first section, as will also be described in more detail below.

In a further embodiment, the switching mechanism of the sample holder transfer device switches the first section of the sample carrier fixing element of the sample holder from the first position to the second position and/or from the second position to the first position by acting upon the second section of the sample carrier fixing element. More particularly, in this embodiment, it is expedient to use a switching mechanism configured to be set into a first position and into a second position, as described above, and to configure the switching mechanism such that, in its first position, no force or a force less than a predetermined force is exerted onto the second section of the sample carrier fixing element, and, in its second position, a force equal to or greater than the predetermined force is exerted onto the second section of the sample carrier fixing element In this embodiment, a threshold force, namely the predetermined force, is necessary to switch the sample carrier fixing element from one position into another. The switching is done by exerting the predetermined force onto the second section of the sample carrier fixing element such that the first section of the sample carrier fixing element switches from a first (closed) position to a second (open) position or vice versa. In this embodiment, it is particularly preferred if the predetermined force exerted onto the second section of the sample carrier fixing element leads to an opening of the sample carrier fixing element, namely to the first section switching from the first position to the second position in order to release the sample carrier or to provide access to an area where the sample carrier is to be placed.

As already mentioned above, in another embodiment, the switching mechanism may be configured to fix the sample holder in a position (loading position), when the switching mechanism is operated to switch the first section of the sample carrier fixing element into its second (open) position. In an embodiment, where the switching mechanism itself is configured to be set into a first position and into a second position, the switching mechanism is configured to fix the sample holder when the switching mechanism is set into its second position. Inserting and removing sample carriers into or from the sample holder is facilitated if the sample holder is in a fixed position.

In an embodiment where the sample holder transfer device comprises a pin, the pin being rotatably mounted in the sample holder transfer device and being rotatable about its longitudinal axis in order to assume, by rotation about a predetermined angular range, two positions corresponding to the first and the second position of the switching mechanism, as already discussed above, the pin may be arranged to be operated by a tool like a screwdriver from essentially the same side from where the sample carrier is to be placed into the sample holder. In this embodiment, a user can easily locate a sample carrier into the sample holder while operating the pin at the sample holder transfer device to either provide access to the area where the sample carrier is to be placed or to fix the sample carrier after insertion of the sample carrier.

As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items and may be abbreviated as "f".

Although some aspects have been described in the context of an apparatus or device, it is clear that these aspects also represent a description of a method of operating such an apparatus or device.

Further embodiments and their advantages are described below in connection with the following figures.

In the following, the figures are described comprehensively, same or analogue reference signs designating same or at least structurally identical components.

<FIG> schematically shows a sample holder transfer device <NUM> for use in cryomicroscopy for transferring a sample holder <NUM> to an analysing or processing unit, only a detail of the sample holder transfer device <NUM> relevant to embodiments of the present invention being shown in <FIG>. In this embodiment, the sample holder transfer device <NUM> is shown with the sample holder <NUM> placed in a dedicated loading position <NUM> of the sample holder transfer device <NUM>. The sample holder <NUM> is configured for holding a sample carrier <NUM> as will be further described in connection with the following figures.

The sample holder transfer device <NUM> is configured to receive a sample holder <NUM>, an example of which is shown in <FIG>. It should be noted that also other kinds of sample holders <NUM> can be used with the sample holder transfer device <NUM> as long as the sample holder <NUM> comprises a sample carrier fixing element, which can be switched from an "open position" to a "closed position" and/or from a "closed position" to an "opened position". In other words, according to the example shown in <FIG>, at least one section 252a of the sample carrier fixing element <NUM> is configured, when in a first position, to fix the sample carrier <NUM> to the sample holder <NUM> (see <FIG>), and, when in a second position, to release the sample carrier <NUM> or to provide access to an area <NUM> where the sample carrier <NUM> is to be placed (see <FIG>).

The sample holder transfer device <NUM> of <FIG> comprises a switching mechanism <NUM> operable to switch the at least one section 252a of the sample carrier fixing element <NUM> of the sample holder <NUM> from the first position to the second position and/or from the second position to the first position.

Embodiments of the switching mechanism <NUM> of the sample holder transfer device <NUM> are now described in further detail.

The switching mechanism <NUM> as shown in <FIG> may be a combination of the following elements: a pin <NUM> being rotatably mounted in the sample holder transfer device <NUM>. The pin <NUM> is rotatable about its longitudinal axis <NUM> and is configured to assume, by rotation about a predetermined angular range, two positions corresponding to a first and a second position of the switching mechanism <NUM> as will be further described in connection with <FIG>. The switching mechanism <NUM> may further comprise a cam element <NUM>. The cam element <NUM> may be connected to the pin <NUM> or be an integral part of it (as shown in the embodiment in <FIG>). The cam element <NUM> may interact with an intermediate element <NUM> such that the intermediate element <NUM> acts upon the sample carrier fixing element <NUM>. In the embodiment shown in <FIG>, the intermediate element <NUM> is another element of the switching mechanism <NUM>. The intermediate element <NUM> may comprise a spring element <NUM> or consist of such a spring element <NUM>.

In other embodiments, other constructions of the switching mechanism <NUM> may be expedient For example, the switching mechanism <NUM> may be an essentially resilient element, similar to the intermediate element <NUM> shown in <FIG>, preferably biased to a position, in which the sample carrier fixing element is in its closed position. An actuating force onto the resilient element would switch the sample carrier fixing element into its open position. In such an example, operation of the switching element would be exerting a direct actuating force onto the resilient element without any further mechanical power transmitting elements. In another example, the switching mechanism <NUM> may mainly be based onto a cam element, like the cam element <NUM> as shown in <FIG>, directly interacting with the sample carrier fixing element in order to switch it from an open position to a closed position or vice versa. Other examples of possible implementations of the switching mechanism <NUM> are described in the Summary section.

As shown in <FIG>, the pin <NUM> of the switching mechanism <NUM> may be configured to be operated by a tool <NUM> like a screwdriver for rotating the pin <NUM> about its longitudinal axis <NUM>. As can be seen from <FIG>, the pin <NUM> of the switching mechanism <NUM> may thus be configured to be set into a first position C and to be set into a second position O, e.g. by rotating the pin <NUM> by <NUM>°. By rotating the pin <NUM> into the second position O, the switching mechanism <NUM> switches section 252a of the sample carrier fixing element <NUM> into its second open position such that access to an area <NUM> where the sample carrier <NUM> is to be placed is provided or a sample carrier <NUM> placed in the area <NUM> is released. This operation shall now be described in more detail.

Rotating the pin <NUM> of the switching mechanism <NUM> from the first position C to the second position O results in a corresponding movement, here a corresponding rotation of the cam element <NUM> connected to the pin <NUM>. The cam surface of the cam element <NUM> may act directly upon the intermediate member <NUM>, which in turn acts upon the sample carrier fixing element <NUM>. It may also be possible that the cam surface of the cam element <NUM> directly acts upon the sample carrier fixing element <NUM>. The intermediate element <NUM> may comprise a spring element <NUM> as shown in <FIG>. The spring element <NUM> may be biased in a direction away from the sample holder <NUM>. In the first position C of the pin <NUM>, the cam surface of the cam element <NUM> exerts no force or a force less than a predetermined threshold force onto the spring element <NUM>. Depending on the shape of the cam surface, this force may increase when rotating the pin <NUM> towards the second position O. In the second position O, this force is equal to or exceeds the threshold force such that the intermediate element <NUM> switches the sample carrier fixing element <NUM> in its second (open) position. In this position, the sample holder <NUM> is ready to receive a sample carrier <NUM>, or, a sample carrier <NUM> already placed in the area <NUM> of the sample holder <NUM> can be removed. Further, in this position, the intermediate member <NUM> exerts a force at least equal to a predetermined force Fs onto the second section 252b of the sample carrier fixing element <NUM> (see <FIG>).

The sample holder <NUM> according to the embodiment of <FIG> comprises two areas <NUM> where sample carriers <NUM> can be placed. In order to place a sample carrier <NUM> onto an area <NUM>, the corresponding first section 252a of the sample carrier fixing element <NUM> needs to be in an open state. The sample carrier fixing element <NUM> according to this embodiment comprises an essentially resilient element, which comprises two sections 252a and 252b, preferably at opposite ends, the first section 252a of which bends backwards if an external force is exerted onto the second section 252b of the sample carrier fixing element <NUM>. When this force is at least equal to a predetermined force Fs, the first section 252a is in an open position such that a sample carrier <NUM> can be inserted in the area <NUM>.

After having placed a sample carrier <NUM> onto an area <NUM> of the sample holder <NUM>, the sample carrier <NUM> needs to be fixed to the sample holder <NUM> in order to transfer the sample holder <NUM> together with the sample to a processing unit or to an analysing unit, examples of such units have been described above. To this end, the switching mechanism <NUM> may be configured to be set into a first position C, in which the switching mechanism switches the at least one section, here the first section 252a, of the sample carrier fixing element <NUM> into its first closed position. As shown in the embodiment of <FIG>, this may be done by rotating the pin <NUM> by means of a tool <NUM> like a screwdriver back to the position C. This leads to a process where the force exerted by the cam surface of the cam element <NUM> onto the intermediate element <NUM> is reduced such that the predetermined force Fs is no longer exerted onto the second section 252b of the sample carrier fixing element <NUM> of the sample holder <NUM>. The cam surface of the cam element <NUM> may be designed such that in the position C of pin <NUM> of the switching mechanism <NUM> no force is exerted onto the second section 252b by the intermediate element <NUM>. Such a situation is shown in <FIG>. The first section 252a of the sample carrier fixing element <NUM> is biased towards the area <NUM> for a sample carrier <NUM>. If no force acts upon the second section 252b, the first section 252a may return to its first closed position. In this position, a sample carrier <NUM> is fixed to the sample holder <NUM>.

<FIG> shows a situation where the sample holder <NUM> is placed in a loading position <NUM> of the sample holder transfer device <NUM>. As can be seen, the switching mechanism <NUM>, more precisely the pin <NUM>, is in the second position O. As explained above, in this position the first section 252a of the sample carrier fixing element <NUM> of the sample holder <NUM> is switched into its second open position allowing insertion of a sample carrier <NUM>. As shown in <FIG>, two sample grids, here so-called "autogrids", may be placed onto the respective areas <NUM> of the sample holder <NUM>.

It may be advantageous if the switching mechanism <NUM> is configured to fix the sample holder <NUM> to the sample holder transfer device <NUM>, when the switching mechanism, as shown in <FIG>, is operated to switch the first section 252a of the sample carrier fixing element <NUM> into its second open position. Thus, during insertion of the sample carriers <NUM> the sample holder <NUM> remains in a fixed position such that a sample carrier <NUM> can be easily inserted and the orientation of a sample carrier <NUM> may be easily adjusted. In the embodiment shown in <FIG>, fixing of the sample holder <NUM> may be achieved through a pushing force of the intermediate element for operating the second section 252b and, simultaneously, for pressing the sample holder <NUM> against sidewalls at the loading position <NUM> of the sample holder transfer device <NUM>.

<FIG> shows a situation similar to that of <FIG> with two sample carriers <NUM> placed onto the respective areas <NUM> of the sample holder <NUM>. The situation shown in <FIG> can be achieved by setting the switching mechanism <NUM>, here the pin <NUM>, into its first position C. The corresponding process has already been described above.

Claim 1:
A sample holder transfer device (<NUM>) for use in cryo-microscopy for transferring a sample holder (<NUM>) to an analysing or processing unit, said sample holder (<NUM>) being configured for holding a sample carrier (<NUM>) carrying a sample,
said sample holder transfer device (<NUM>) being configured to receive the sample holder (<NUM>) in a predefined place at a loading position (<NUM>), wherein said sample holder transfer device (<NUM>) comprises a transfer rod (<NUM>), wherein the transfer rod (<NUM>) is configured to be connected to the sample holder (<NUM>) for transferring the sample holder (<NUM>) to the analysing or processing unit,
the sample holder (<NUM>) comprising a sample carrier fixing element (<NUM>), at least one section of the sample carrier fixing element (<NUM>) being configured, when in a first position, to fix the sample carrier (<NUM>) to the sample holder (<NUM>), and, when in a second position, to release the sample carrier (<NUM>) or to provide access to an area (<NUM>) where the sample carrier (<NUM>) is to be placed,
said sample holder transfer device (<NUM>) further comprising a switching mechanism (<NUM>) operable to switch the at least one section of the sample carrier fixing element (<NUM>) of the sample holder (<NUM>) from the first position to the second position and/or from the second position to the first position.