JP2002544515A - A device for determining the contact angle of a drop located on a support - Google Patents

Abstract

(57) [Summary] The present invention is an apparatus for specifying the contact angle (γ) of a drop (2) applied to a support (1), and the specified drop (2) is applied to the support. The present invention relates to a type in which a metering device (3) for carrying out, a camera (4) corresponding to an evaluation device and a display unit (5) are provided. The device comprises a support cradle or casing mounted on a support (1) supporting a metering device (3), a lighting device (6), a camera (4), an evaluation device and a display unit (5). By being formed as a hand-held device, a compact and easily operable arrangement is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for specifying a contact angle (generally also called a wetting angle) of a drop located on a support table by using a camera for image formation of a drop and an evaluation apparatus. .

Such an apparatus is disclosed in Patent Abstracts of Japan, Section P, Vol. 9 / No. 227 (
1985) P-388, JP-A-60-085353. In this known device, the contact angle of a sample drop applied to a support in the form of a test surface is determined from a side view by optical imaging. For example, a camera is used for optical imaging, and the evaluation is performed by an image processing system connected to a calculator. The drops are applied to a support formed in the casing part and a calculator connected to the monitor is located outside the casing part.

A similar device is disclosed in Patent Abstracts of Japan, Section P, Vol. 13 / No. 370 (19
89) JP-A-01-126523 of P-920, Patent Abstracts of Japan, Se
ction P, Vol. 17 / No. 681 (1993) P-1660, JP-A-05-232009,
It is also known from Japanese Patent Application Laid-Open No. 08-050088, atent Abstracts of Japan, (1996), and from German Patent Application DE 34 41 317 A1.

[0004] A disadvantage of existing methods and devices is that the alignment of the test surface, the placement of the device, and the adjustment of the device are laborious.

Advantages of the invention The object of the invention is therefore to improve a device for determining the contact angle of a drop located on a support, of the type described at the outset, to simplify the construction of the device, It is another object of the present invention to provide a device in which the operation at the time of measurement is reduced.

[0006] This object is achieved by a device having the features as set forth in the characterizing part of claim 1.

[0007] With such a configuration, a compact and movable measuring unit that can be easily operated is obtained, and the measuring unit can perform measurement on various supports without any problem. Adjustment and operation are simplified based on the mounting of components in the hand-held device. Measurement can be performed in a small space.
For example, a structural height of less than 200 mm, a depth of 90 mm and 120
mm width is achieved.

[0008] The compact construction and simple operation are aided mainly by the fact that the camera is formed as an intelligence camera with an integrated processor for image evaluation, a memory and an input / output unit.

[0009] In order for the support base or the casing to be stably mounted on the support base (1),
The embodiment comprising a mounting device for maintaining a set or settable working distance between the surface of 2) and the camera objective lens (4a) is simple and reproducible. This contributes to quick measurement. According to an advantageous configuration, the mounting device comprises a frame provided with legs (9) arranged in the form of a tripod. The provision of spacing pins (10) in the support cradle or casing to maintain a predetermined spacing helps to maintain a preset or pre-settable spacing.

[0010] Because of the space-saving construction and the low energy consumption, the lighting device (6) is preferably provided with a light-emitting diode arrangement (6.1). According to an advantageous embodiment of the various lighting devices for evenly illuminating the drop, a partially transmissive mirror positioned at an angle is provided for directing the light of the lighting device (6) to the drop (2). Either provided or a ring light arrangement is provided.

A compact design is facilitated by the metering device (3) having a piezo pump of the drop-on-demand type or a pump of the jet-on-demand type. With such an embodiment, mechanically moving parts are largely avoided and defined drops are formed with simple control.
According to an advantageous embodiment, a piezo pump has a micromachined, silicon-provided system with an embedded piezo element.

According to an advantageous embodiment for a more accurate measurement, the operation of the metering device (3) and the image capture by the camera (4) are coordinated with one another in a time-controlled manner by the control device.

[0013] A more accurate measurement is aided by the provision of an automatically controlled spacing device for adjusting the spacing between the camera objective lens (4a) and the drop (2).

In the evaluation, it is advantageous to use a state in which the microdroplets form an almost ideal spherical crown. This allows a known volume (eg 2 μl) to be observed in FIG.
) From each one of the geometric sizes (base diameter, sphere diameter or height) of the applied sample drops, the effective geometric-trigonometric relationship for the crown (FIG. 4)
a) is used to specify the contact angle. Due to the increased mathematical effort, it is possible to determine the contact angle even if the drop is different from the ideal shape of the crown.

[0015] Particularly advantageously, the contact angle is determined from the base diameter observed from above in plan view (even from below in the case of a permeable specimen). In addition to a simple form of observation that results in a device that can be used flexibly, the drop brought to the support, e.g. a glass plate, changes its onset-base diameter until just before the drop disappears even during the vaporization process. Since the phenomenon of maintaining is used, a measurement without a time problem is provided. This is actually the case in most cases for contact angles below 90 °.

For contact angles greater than 90 °, the diameter observed in plan is no longer the base diameter of the crown, but the diameter of the sphere.

This is taken into account in the evaluation algorithm. Here, the same preconditions are taken into account for the time interval between drop application and measurement as in the case of the already common methods.

[0018] The diameter of the sample droplet imaged with good contrast is determined using image evaluation software, and the contact angle is calculated and displayed using an algorithm stored in a calculator, and possibly further processed. Is done.

If deviations from the ideal circular contour of the crown base occur due to minor inhomogeneities of the test surface, which are not excluded in some cases, the evaluation advantageously
Based on the best circular fit, a determined contact angle in the range of drop sizes is provided, which is actually generally desired. According to another advantage, the measurement can be performed to a certain extent, even on inclined, non-flat test surfaces, for example on the windshield of a vehicle.

In addition to calculating the base diameter from the plan view and calculating the diameter of the sphere for contact angles greater than 90 °, a side view of the sample drop can also be used for the calculation. The side view allows the calculation of the drop height and also the calculation of the diameter of the sphere for contact angles below 90 °. Each of these sizes is again used in conjunction with the known drop volume for the calculation of the contact angle. For example, for a known drop shape approximating a spherical cap, the contact angle can be determined from two separately determined geometric sizes, such as height and base diameter, even if the exact drop volume is not known.

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 3 shows the definition of the contact angle γ of the spherical drop 2 applied to the support 1, as well as the drop 2 and the support The basic diameter _dBa and the height h in the region of the interface between are shown. Note that the symbol d _Ku indicates the diameter of the droplet sphere. Here, the contact angle γ is smaller than 90 °.

FIG. 4 a shows the base diameter d _Ba of the spherical _crown drop, the diameter d _{Ku of} the sphere and the height h of the drop.
Are shown as a function of the contact angle γ.

The diagram of FIG. 4 b shows the relationship between the diameter measured from above the test drop 2 and the contact angle γ determined from this diameter. For contact angles γ up to 90 °,
The base diameter _dBa of the drop crown is used, whereas for angles greater than 90 ° the diameter d _Ku of the sphere of the drop 2 in a crown _shape is used.

FIG. 5 schematically shows a measuring apparatus for specifying a contact angle γ in a basic arrangement of an embodiment provided with an “intelligent camera; intelligent camera” in which a camera and an image evaluation system are combined. Is shown. A drop 2 having a precisely set drop volume, for example manually or automatically provided by means of a metering device 3, is imaged by a conventional objective lens 4a or a telecentric objective lens 4a and an intelligence camera 4. It is formed. When a simple camera 4 is used, an external calculator (not shown) for performing an evaluation is provided between the camera 4 and the display unit 5.

In the evaluation unit, from the set volume and the detected geometric data (base diameter d _Ba , sphere diameter d _Ku , height h), two of these sizes are combined to determine the contact angle. Can be

The display unit 5 shows a drop image in a plan view and a contact angle γ obtained below the image.

In addition, the measuring device preferably has an illuminating device for illuminating the droplet 2, seeing the droplet 2 in plan view (see FIGS. 1, 2 a, 2 b). . With a permeable support,
Illumination can also be performed from the back surface (lower surface).

FIGS. 1, 2 a and 2 b show schematically a device for determining the contact angle of a drop 2, formed as a hand-held device. On a support base or casing (not shown in detail) mounted on a support 1 for supporting the drops 2, a metering device 3, a camera 4 with a camera objective 4a, and a flat display unit 5, e.g. Possible liquid crystal display and light emitting diode arrangement 6.1
A semi-transparent mirror 8 for directing light to the drop 2 on the one hand and observing the drop 2 with a camera on the other hand, and a tripod leg 9 arranged on the frame. The mounting device is mounted as one unit. As can be seen from the two different side views, FIGS. 2a and 2b, the hand-held device so formed additionally comprises an electronic device 7 and another electronic device 7.1. These electronic devices are, for example, part of a control device, which further comprises a processor or a calculator integrated in the camera 4. The camera 4 is formed as an intelligence camera. In the area of the drops 2, in order to ensure that the working distance is maintained, for example in the case of a curved support 1, an additional spacing pin 10 may be provided in this area. The leg 9 and the spacing pin 10 are formed to be adjustable.

The main component of the hand-held device is a so-called intelligence camera 4, which is a combination of a camera 4, a camera optics 4 a and an integrated calculator for image evaluation. . Further, the lighting device 6 can be directly attached to the camera.

The lighting device is used to create reproducible lighting characteristics for illuminating the drop 2 without shadows and reflections in the surroundings. This is advantageously obtained by means of a light-emitting diode arrangement which is reflected at the side by a partially transmissive mirror 8, for example a plane glass plate inclined at 45 °, the light-emitting diode arrangement having a small required output as well as small dimensions. are doing. A ring light arrangement may be selectively provided.

The metering device 3 for producing a defined volume of drops 2 is advantageously provided with a piezo pump of the drop-on-demand type, which drops on demand, by means of which the required volume is reduced. It can be metered with an accuracy of plus or minus 2%. In this case, it is not necessary to place the drops 2, but rather the drops 2 can be metered at precise times with a free jet through a distance of up to 15 mm. In principle, it is also possible to use other free-jet systems, for example of the jet-on-demand type, which jets on demand. In such a free-jet system, however, care must be taken that the kinetic energy exerted by the metering on the drops 2 present is so small that it does not affect the drop contour. In the drop-on-demand type, the danger is very much smaller due to the very small size of the drops.

The drop-on-demand system advantageously consists of micro-machined silicon with embedded piezo elements. By applying a predetermined voltage to this piezo element, deformation and pressure build-up in a preferably small storage chamber (for example 800 nl) occur, so that a drop of approximately 1 nl at the tip of the pump flows out. The connected control unit controls the pump, which itself is automatically responded to by the intelligence camera 4 via the control device.

With this configuration, it is not necessary to provide a mechanically moving part inside the hand-held device, and the size of the hand-held device can be kept extremely compact. This is because the dimensions of the pump do not exceed 20 mm. The liquid reservoir is preferably mounted at the height of the outlet tip and is preferably formed as a tube, so that during transport the outflow can be prevented by the coupling of the liquid using the capillary forces of the tube. Approximately 100 measurements can thus be performed with a 2 μl drop volume without post-filling.

As an alternative, a metering device 3 with a conventional measuring piston is also conceivable. The metering device can be operated manually or can be controlled and driven by a set servo system.

The configuration of the hand-held device is particularly compact when telecentric optics are eliminated based on a suitable mechanism for controlling the spacing, and compact and conventional optics are used. However, in this case, it is necessary to adjust the distance to the test piece. The adjustment is preferably made automatically. Mechanical and / or electric regulating devices can be used, in which case an embodiment with a space-saving leaf spring is advantageous.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a measuring device for specifying a contact angle of a droplet.

2A is a side view of the measuring device, and FIG. 2B is a front view of the measuring device.

FIG. 3 is a side view showing a droplet provided on a support base.

FIG. 4a is a diagram showing the relationship between the contact angle of a drop and another geometric data.

FIG. 4b is a diagram showing the relationship between the contact angle of a drop and another geometric data.

FIG. 5 is a schematic view showing an arrangement of a device for applying a droplet and for specifying a contact angle.

[Explanation of symbols]

Reference Signs List 1 support base, 2 drops, 3 metering device, 4 camera, 4a objective lens, 5 display unit, 6 lighting device, 6.1 light emitting diode arrangement,
7,7.1 electronic device, 8 a mirror, 9 legs, 10 spacing pins, _{d Ba} basal diameter, h the height, diameter _{d Ku} sphere, gamma contact angle

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] July 27, 2000 (2000.7.27)

[Procedure amendment 1]

[Document name to be amended] Drawing

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[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] June 29, 2001 (2001.6.29)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

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──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), JP, US (72) Inventor Werner Free Germany Untergruppenbach Happenbacher Strasse 58 (72) Inventor Oliver Prowl Germany Ostfildern Brunenstrasse 50 (72) Inventor Claus Marx Germany Schuttgart Holderbuschweg 30 (72) Inventor Norbert Streible Germany Leonberg Paulinenstraße 30 (72) Inventor Wolf Reinhard Germany Republic Hamburg Borusute error Shose 85-99 Ah

Claims (11)

[Claims] An apparatus for specifying a contact angle (γ) of a drop (2) applied to a support (1), wherein a prescribed drop (2) is applied to the support (1). A type in which a metering device (3) for scrubbing, a camera (4) corresponding to an evaluation device, and a display unit (5) are provided, wherein the device is the metering device (3) ), A lighting device (6), the camera (4), the evaluation device, and the display unit (5), as a hand-held device having a support frame or a casing mounted on the support table (1). An apparatus for determining the contact angle of a drop located on a support, characterized in that it is formed. 2. The device according to claim 1, wherein the camera is formed as an intelligence camera with an integrated processor for image evaluation, a memory and an input / output unit. 3. The setting or setting between the surface of the drop (2) and the camera objective lens (4a) for the stable mounting of the support cradle or casing on the support (1). Equipped with a mounting device to maintain possible working intervals,
The device according to claim 1. 4. The device according to claim 3, wherein the mounting device comprises a frame provided with legs (9) arranged in the form of a tripod. 5. The device according to claim 3, wherein a spacing pin (10) is provided on the support cradle or the casing to maintain a predetermined spacing. 6. The device according to claim 1, wherein the lighting device (6) comprises a light-emitting diode arrangement (6.1). 7. An obliquely located partially transmissive mirror (8) or a ring light arrangement is provided to direct the light of said illuminating device (6) to the drop (2). Apparatus according to any of the preceding claims, wherein 8. The metering device (3) comprises a drop-on-demand type piezo pump or a jet-on-demand type pump, or the metering device (3) is manually operable. 8. The device as claimed in claim 1, wherein the device comprises a conventional measuring piston which can be driven or controlled by a servo system. 9. The piezo pump comprises a micromachined silicon-applied system with an embedded piezo element.
An apparatus according to claim 8. 10. The operation of the metering device (3) and the taking of images by the camera (4) are time-controlled by a control device and are coordinated with each other.
10. The device according to any one of claims 1 to 9. 11. An automatically controlled distance adjusting device for adjusting the distance between the camera objective lens (4a) and the drop (2) is provided.
The device according to any one of the preceding claims.