RU2297078C1 - Three-coordinate positioner - Google Patents

Abstract

FIELD: piezoelectric voltage-to-mechanical-displacement converting devices.

SUBSTANCE: proposed positioner has object holder and case. The latter mounts three drives incorporating at least one biform member connected through first flexible pusher to movable member. Biform members are, essentially, stacks, each incorporating piezoelectric disk joined along plane with metal diaphragm. Object holder is mounted on fixed member. Object holder can be installed on movable member with aid of lever. Pushers have different stiffness. Piezoelectric disks and metal diaphragms have holes in vicinity of their connection to flexible pushers.

EFFECT: extended scanning range, enhanced reliability.

4 cl, 2 dwg

Description

The invention relates to piezoelectric devices for converting electrical voltage into mechanical movement and can be used in scanning probe microscopy.

A known positioner (scanner), for example, for a scanning probe microscope (SPM) with a scanning field of up to 100 × 100 × 10 μm ³ , built on the basis of piezotubes [1].

The disadvantage of this device is the small range of movement, especially along the coordinate (Z), compared with the movement in the plane (XY).

Also known is a three-coordinate positioner containing a housing on which piezobimorphs of movement along the X and Y coordinates are installed, as well as a piezotube for moving along the Z coordinate, connected by elastic rods with a movable core. In this case, the object is mounted on a piezotube [2].

This device is selected as a prototype of the proposed solution.

The first disadvantage of this device is that the range of its movements along the coordinates X, Y, Z does not exceed 30 × 30 × 5 μm ³ .

The second disadvantage is the low reliability associated with the fragility of piezoelectric ceramics, especially in places of connection with metal structural elements.

The third drawback is the use of an additional piezotube to move along the Z coordinate, which complicates the design and also reduces its reliability.

The technical result of the proposed solution is to increase the scanning range and increase the reliability of the device.

The essence of the invention lies in the fact that in the three-coordinate positioner, consisting of an object holder and a housing, on which a first drive is fixed in a first coordinate, comprising at least one first bimorph element connected by a first flexible pusher to a movable element, the second drive in the second coordinate containing at least one second bimorph element, while the third drive along the third coordinate is connected by a third flexible pusher with a movable element, as the first and second bimorph The components are used in packages, each of which contains a piezoelectric disk (first and second) connected in a plane with a metal membrane (first and second), while the third drive is made in the form of a package containing a third piezoelectric disk connected in a plane with a third metal membrane , and mounted on the housing, and the holder of the object is mounted on a movable element.

There is an option in which the object holder is mounted on the movable element by means of a lever.

A variant is possible in which the pushers have different stiffness.

There is also an option in which piezoelectric disks and metal membranes have holes in the area where they are connected with flexible pushers, and metal membranes are mounted on the body with flanges.

Figure 1 shows the three-coordinate positioner.

Figure 2 shows the three-coordinate positioner as part of a scanning probe microscope.

The three-coordinate positioner contains a housing 1, on which the first 2, second 3 and third 4 drives are mounted, respectively, along the first X, second Y and third Z coordinates. Each drive is made in the form of a package (bimorph element), consisting of a piezoceramic disk (first 5, second 6 and third 7), connected in a plane with the first 8, second 9 and third 10 metal membranes. As the membrane materials, bronze or, for example, stainless steel can be used. Disks 5, 6, 7 with membranes 8, 9, 10 can be connected by means of glue, for example, “UHUplus endfest 300”, and membranes 8, 9, 10 with housing 1 can be soldered, spot-welded or union flanges (in FIG. 1 are not shown).

Holes 11 can be made in disks 5, 6 and 7, and adapters 12, 13 and 14 are fixed on membranes 8, 9 and 10, for example, by soldering, spot welding or fixing screws (not shown). In the membranes 8, 9 and 10 can also be made holes (not shown conditionally) for fixing adapters in them. Adapters 12, 13 and 14 are connected to the first 15, second 16 and third 17 elastic pushers made of spring material. It should be noted that at least one pusher may contain elastic joints 18 and 19 to select the optimal stiffness. A movable element 20 is fixed on the pushers 15, 16 and 17, on which, for example, by means of the lever 21 is mounted the holder 22 of the object 23. Parts 15, 16, 17, 18, 19, 20, 21 and 22 can be connected by means of press fittings, welding soldering, glue, etc.

It should be noted that in order to fulfill the exact characteristics of the positioner, certain ratios of the stiffness characteristics of its moving elements must be observed.

We denote the bending stiffness of the packages (piezoelectric disk - metal membrane) for the X, Y, and Z axes as K1, the bending stiffness of the pushers 15 and / or 16, respectively, by the X and Y coordinates, we denote K2 (we consider them the same), the bending stiffness of the pusher 17 by coordinate Z is denoted by K3, and the longitudinal stiffness of the pushers 15 and 16 is denoted by K2 *, K3 *, respectively. Then, to ensure movement, for example, along the Z coordinate, it is necessary that the relation

And to move along the X or Y axis, it is necessary that

In the latter case, the pusher 17 does not bend, but the actuator 4 (package) is bent, on which the pusher 17 is mounted, while the point of its connection with the actuator 4 plays the role of a hinge around which the pusher 17 rotates. In the described construction, the relation

This is done in order to reduce uncontrolled displacements in the X, Y plane during sharp movements along the Z coordinate when working in the SPM. Indeed, provided that the pushers 15 and 16 do not change their length, the pusher 17 would have to bend under the action of the drive force 4. However, when condition (3) is satisfied, the pusher 17 does not bend, but drives 2 and 3 to bend, moving in a straight line.

The three-coordinate positioner 24 (Fig. 2) can be used as part of a scanning probe microscope containing a preliminary proximity system 25, a control unit 26 with a holder 27 of the probe 28, and a sample 29 mounted on the holder 22. A variant is possible in which the holder 22 can be the probe is fixed, and a sample (not shown) is mounted on the holder 27. In addition, the cap flanges 30 and 31 can be installed on the housing 1 for the purpose of fastening the membranes.

The device operates as follows. When a control voltage is applied to one of the piezoceramic disks, for example 5, it changes its size, and the membrane 8 bends under the action of forces from its side, moving the pusher 15 attached to it. In this case, the pushers 16 and 17 are bent and do not impede this movement. In addition, membranes 9 and 10 are also slightly bent, forming flexible backlash-free joints. The movable element 20 makes a complex motion along the X coordinate, close to rectilinear. When voltage is applied to other disks, the corresponding pushers move in proportion to the applied stresses independently of each other, and the element 20 moves along the coordinates Y, Z. The movable holder 22 moves along with the end of the lever 21. Moreover, the movement in the horizontal plane is greater than vertical due to the effect of the lever. One shoulder of the lever is the pusher 17, the other shoulder of the lever is the element 21.

As part of the SPM (figure 2), the positioner 24 moves the sample 29 relative to the probe 28, so that it is possible to analyze the surface of the sample and local impact on it (for more details on the work of the SPM see [3, 4, 5]).

The use of packages consisting of piezoceramic disks and metal membranes increases the range of movement of the device with the same dimensions (about 40 mm in diameter) to 150 × 150 × 30 μm ² and its reliability due to the presence of metal in the package. In addition, the attachment of metal membranes to the housing, as well as their connection with the adapters is more reliable than in the prototype, in which this connection is made through brittle ceramics.

Using in the device one packet for each coordinate increases the linearity of positioning by eliminating inconsistencies in the movements of pairs of piezobimorphs as in the prototype.

Using the lever in the drive increases the range of movement of the object and allows you to adjust it.

The use of pushers with different stiffness allows to increase the accuracy of movement at high values by optimizing the mutual influence of the pushers.

Making holes in piezoelectric disks and metal membranes increases the reliability of the device by reducing their force interaction during long-term operation resulting from plastic deformation of disks and membranes.

The use of union flanges ensures electrical safety and reduces electrical interference from piezoelectric disks.

LITERATURE

1. Patent RU 2199171, 2003.

2. A.S. SU No. 1453475, 1989.

3. Probe microscopy for biology and medicine. V.A. Bykov et al., Sensory Systems, vol. 12, No. 1, 1998, pp. 99-121.

4. Scanning tunneling and atomic force microscopy in surface electrochemistry. Danilov A.I., Advances in Chemistry, 64 (8), 1995, p. 818-833.

5. Scanning tunneling microscope instrumentation. Y. Kyk, P. Sulverman. Rev. Sci. Instrum. 60 (1989), No.2, 165-180.

Claims (4)

1. The three-coordinate positioner, consisting of an object holder and a housing on which the first drive is fixed along the first coordinate, containing at least one first bimorph element, connected by means of the first flexible pusher with a movable element, the second drive along the second coordinate, containing at least one a second bimorph element, the third drive being connected along the third coordinate by a third flexible pusher with a movable element, characterized in that as the first and second bimorph elements t packages, each of which contains a piezoelectric disk (first and second) connected in a plane with a metal membrane (first and second), while the third drive is made in the form of a package containing a third piezoelectric disk connected in a plane with a third metal membrane and fixed on the housing, and the holder of the object is mounted on a movable element. 2. The device according to claim 1, characterized in that the object holder is mounted on the movable element by means of a lever. 3. The device according to claim 1, characterized in that the pushers have different stiffness. 4. The device according to claim 1, characterized in that the piezoelectric disks and metal membranes have openings in the zone of their connection with flexible pushers, and metal membranes are mounted on the body with flanges.

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