Our DS3252 double-dosing module performs fully automated surface free energy (SFE) determinations, using an automation program in our ADVANCE software. The dosing unit has two pressure dosing mechanisms working in parallel, each simultaneously dispensing one drop of the test liquids water and diiodomethane onto the sample.

For carrying out the drop shape analysis, the image field of the high resolution camera is split into two video windows for viewing both drops at the same time in order to analyze the drops in parallel. The software then uses the resulting contact angles to calculate the SFE of the solid. The entire process, from the point when dosing starts up to the SFE calculation, is fully automatic and complete within a second. For this innovative measuring method, we hold a patent regarding the novel dosing technology.

The kinetic energy of the dosing process – despite its speed – is equivalent to gently dispensing a drop from a dosing needle. Most importantly, this noncontact method eliminates the risk of contamination or damage caused by inadvertently touching the sample. Cartridges, that operators can remove quickly and fill directly with test liquids, make the dosing system easy to handle. One filling is enough for approximately 1000 SFE determinations.

The dosing unit DS3252 requires our CF03 USB camera.

In addition to the dosing unit, the following components are also included in the scope of supply:

• 10 cartridges with Luer-Lock connector: 5 transparent for water and 5 brown for diiodomethane

• 10 disposable syringes (1 mL) with Luer connector

• 10 Luer-Lock adapters

• 1 transparent and 1 brown 25 mL glass bottle for test liquids

• Tool for easy removal of cartridges from the dosing unit

• Cleaning set for the dosing valves

The first three positions on this list are also available as spare part set SP52.

The precision glass syringe SY20 is used for our manual dosing unit DS3205 or software-controlled dosing units D03211/DO4011 for one liquid. The gas-tightness of the syringe plunger and the Luer-Lock connector ensure that drops are dosed in a controlled manner even with low-viscosity liquids.

The syringe SY3601 can be fitted to many of our manual and software-controlled dosing solutions and can be used for almost all liquids. It is particularly suitable for dosing highly contaminating substances such as adhesives or paints. The Luer connector ensures safe, gas-tight connections to needles and other dosing components. The syringe is supplied in sets of 100.

The choice of a suitable needle diameter maximizes the accuracy of surface and interfacial tension measurements using the Pendant Drop method.
For this purpose, the needle set NE96 (top picture) contains stainless steel needles with a length of 38 mm and different outside diameters (0.5/1.0/2.0/3.0 mm), in order to achieve an ideal drop shape for analysis in every measuring range.In the set NE93 (bottom picture), the four different needles are also PTFE-coated and optimize the analysis of liquids with good wetting properties. The coating prevents external wetting of the needle and ensures absolutely symmetrical drop shapes.

The needle assortment NE94 provides a range of suitable needles for measuring contact angle as well as surface and interfacial tension (SFT/IFT) using the Pendant Drop method. Steel, PP and PTFE needles with a length of 38 mm and different diameters enable optimal dosing for solids and liquids with different wetting behavior. All needles have a Luer-Lock connector for secure attachment to all single and multi-dosing units.

Contents of the set:

• 5 steel needles with 1.8 mm diameter (SFT/IFT)

• 5 steel needles with 0.5 mm diameter (contact angle)

• 5 PTFE needles with 2.0 mm diameter (SFT/IFT)

• 5 PTFE needles with 1.0 mm diameter (SFT/IFT)

• 5 PTFE needles with 0.5 mm diameter (contact angle)

• 5 PP needles (flexible syringe) with 0.7 mm diameter (contact angle)

The set NE97 with three J-shaped needles has been put together especially for measurements with the Captive Bubble method and with rising drops. The 0.5 mm diameter needle enables highly energetic, structured or pre-wetted surfaces (e.g. contact lenses) to be analyzed. With two further needles (1.0 and 2.0 mm), the interfacial tension can be measured on rising drops. This enables systems such as crude oil/water, in which the lighter phase is not transparent, to be analyzed optically.

The needle NE50 with 5 µm internal diameter has been designed for the manual dosing of small volumes below the microliter range. The water-repellent surface lets drops detach easily from the needle and allows to place them accurately in the required position on your sample. Please also see our accessories for dosing drops in the picoliter range and the analysis of minute probes using microscope lenses.

The glass cuvettes SC01 and SC02 accommodate the bulk phase when measuring the interfacial tension using the Pendant Drop method. When measuring surface tension, the cuvettes screen the dosed drop against air currents. With the smaller cuvette SC01 (top picture), this is also ensured by an additional cover which additionally prevents the drop evaporating. The smaller cuvette SC01 can be used when taking measurements in a temperature controlled chamber for measuring interfacial temperature as a function of temperature.

Because of its larger design, the SC02 (bottom picture) is particularly suitable for measuring the contact angle in the bulk liquid. Both cuvettes are made of high-quality optical glass. As a result, drops are displayed without distortion, thus guaranteeing an accurate analysis of the drop shape.

Overview of both products:

• SC01: Cuvette with inner dimensions 20 × 20 × 24 mm (W × D × H), with cover, can be used in temperature controlled chambers

• SC02: Cuvette with inner dimensions 36 × 36 × 30 mm, particularly suitable for measuring the contact angle in the bulk liquid.

The tilting device PA4020 is our special unit for the flexible analysis of inclined surfaces with the DSA25. The tilt which leads to the drop running off as well as the advancing and receding contact angle of the moving drop lead to conclusions concerning roughness and adhesion of the sample.

Furthermore, the roll-off angle is informative for ultra­hydrophobic samples and is accurately measured with slow tilt movements. To determine this parameter precisely, our ADVANCE software detects the coordinates of the three-phase points, which indicate the position of the drop in the camera image. The change in these coordinates can be measured accurately, yielding an objective criterion for detecting the roll-off angle.

As the whole instrument is tilted, the surface is always in the same position relative to the lens. This makes the video evaluation very easy, and changes in the drop can also be tracked visually. Almost all other measuring methods and options provided by your instrument can be used without changing the setup. The tilting movement and related measurements can be embedded in automatic measuring sequences.

• Angle of inclination up to 90° with a resolution of 0.1°

• Tilt speed from 0.1°/s to 4.5°/s

The sample table PS3244 is designed for the ultra-precise positioning of small samples. Manual fine drives for the x- and y-direction enable the table to be moved to the required measuring position with pinpoint accuracy. Samples with heights up to 2 mm can be securely fixed using the versatile, attachable sample holder.

The vacuum table ST3210 has a permeable tabletop through the pores of which samples are drawn homogeneously on a large area of 150 × 220 mm. The table ensures a flat and easy-to-analyze surface when carrying out measurements on films as well as samples with only low elasticity or softness. It can be mounted flexibly on horizontal movement axes or (with DSA100 and DSA30) on a rotation axis. A vacuum pump, which is required for operating the table, can be obtained from us.

We have developed the sample holder and dosing set ST10 for measuring contact angle in a bulk liquid phase. Gas bubbles (Captive Bubble) or drops are dosed beneath the sample with the help of the set’s special needle and cuvette, e.g. for analyzing hydrogels and highly energetic and structured surfaces. The special holders optimize measurements on contact lenses, films and textiles as well as on rigid samples.

The suction plate ST01 ensures that a smooth, flat surface is achieved with foils, films and similar samples. This guarantees a reliable and precise measurement of the contact angle on such soft, flexible materials. The wide area of 100 × 100 mm creates space for a large number of dosed drops. A vacuum pump, which is required for operating the plate, can be obtained from us.

The vacuum pump VP01 is a useful aid which can be used with many of our measuring instruments for the following purposes: 

• Degassing of liquids for picoliter dosing units or for interfacial rheology to prevent the formation of troublesome air bubbles (with additional connector set SP01)

• Removal of dosed drops when measuring contact angle to enable several positions along the optical axis to be analyzed (with additional connector set SP01)

• Flushing the tiny dosing opening of picoliter dosing units (with additional connector set SP01)

• Producing the vacuum for fixing foils and films for the suction table ST01

• Use of the vacuum for the filter base cleaning tool TO4501 for the Dynamic Foam Analyzer – DFA100

The powder sample holder ST03 is a sample table adapter with three depressions for measuring the contact angle on powder beds. The depressions are filled with powder which is then smoothed out resulting in flat surfaces for dosing liquids. The three separate areas enable at least three positions to be analyzed without being affected by adjacent drops, even in the case of absorbent powders. Please also refer to the alternative Washburn-Method for powder contact angle with our Force Tensiometer – K100.

We have designed the special sample holder ST04 for measuring contact angle on foils and paper. The clamping device ensures an ideally smooth, flat surface, even with corrugated and rolled samples. The holder takes samples with a surface area of 80 × 80 mm and a thickness of up to 4 mm.

When measuring the contact angle on uneven samples, dosing must be carried out on a raised point in order to obtain an analyzable shadow image of the drop. For this purpose, the sample table adapter ST08 has a domed shape, over which the samples are tightened with the help of a magnetic clamping device. Combining with horizontal axes enables several measurements to be made in quick succession by dosing accurately along the crest.