Precision Contact Angle Tensiometers

Smart Interfacial Measurement Solutions for Wettability and Adhesion


More Information – Attension Theta Optical Tensiometers

Attension Theta Optical Tensiometers are designed to simplify workflows and deliver accurate, repeatable data with ease. Eliminate the need to have multiple instruments for different measurements with the modular Attension systems that offer a vast assortment of plug-and-play modules, and easily upgrade with additional modules at any time. From a fully manual configuration, to the most advanced, fully-automated system, the Attension Theta optical tensiometers can be equipped to provide the optimal setup for your application.

Contact angle measurements on small areas

Contact angle measurements are used to characterize the wettability of a surface (sometimes described in terms of hydrophobicity and hydrophilicity). These measurements provide critical data for scientists across a wide range of applications including biomedical coatings, enhanced oil recovery (EOR), and printed circuit boards (PCBs), among many others.

The most common method used to determine the wettability of a surface is the sessile drop.

In a sessile drop measurement, a droplet of a few microliters in volume is deposited onto a sample surface and is imaged by an optical camera. The image of the droplet is then analyzed by software to determine the contact angle between the droplet and the baseline surface material, as shown in the screen capture on the right from the OneAttension software.

As the droplet sits on the surface, it usually creates a baseline width from around 1 millimeter to a few millimeters, depending on the wettability properties of the surface material. In most cases, this baseline width range is suitable, and several measurements can be taken on the same sample.

However, in some situations, contact angle measurements must be performed using much smaller surfaces, on which a one millimeter-wide droplet would not fit. The Theta Pico was designed to provide a solution for these challenges by delivering the same ease of use, accuracy, and experimental repeatability as the other Attension Theta tensiometers, but dispensing picoliter volumes for contact angle measurements.

Picture of the Attension Theta with Picoliter Dispenser

The Attension Theta Pico can create droplets as small as 20 picoliters, with drop diameters less than 100 µm, depending on the contact angle

Picoliter dispenser can create as small as 20 pl droplets

The Picoliter Dispenser is based on piezo-driven inkjet printing technology, and can dispense droplets as small as 20 picoliters. With a volume this small, a drop diameter of less than 100 µm is possible, depending on the contact angle formed.

The Theta Pico leverages the Attension Theta Flow‘s hallmark automation capabilities to remove user-dependent variation in contact angle measurements, enabling each experiment to be repeated with a high level of precision.

In this video, the picoliter dispenser was pre-programmed along with the motorized XYZ-stage to take several contact angle measurements with one click of a button. You will see 3 drops deposited in a row, 0.5 mm apart from each other, along with the real-time data acquisition on the graphical display at the bottom-right of the screen.

Characterizing properties of functional surfaces and coatings

Nano-engineered functional surfaces are studied for a wide range of applications. Contact angle measurements are often used to define the wettability and functionality of these novel surfaces. Explore these resources to learn more about the different experimental methods supported by the Attension Theta optical tensiometers, and what the data can reveal about the material properties of surfaces.

GIF of pages flipping from Adhesion White Paper

Adhesion is important in all applications where two different materials are bonded together, such as with paint, varnish, or adhesives. Wettability is required for good adhesion, and because of this, contact angle and surface free energy measurements are often used to evaluate the surface before the bonding process. What information can be gathered from these tests, and what does it mean?

The water break test is an industry standard for measuring the cleanliness of a surface, which is an important metric for determining whether or not a surface is ready for the next process step. However, the test has several limitations which make it highly user-dependent, and the traceability of the test results is not possible. For this reason, other tests for cleanliness are necessary.

Diagram of water contact angle interpretation

Different types of surface treatments are commonly used to increase wettability of surfaces, which enables better adhesion when bonding, applying coatings, or printing. Contact angle measurements detect any possible problems in the surface treatment process early on, providing valuable information for quality control.

Despite good process planning, adhesion problems sometimes occur. To catch the possible problems early on, quality control processes for the treated surface should be implemented. Since wettability is a prerequisite for good adhesion, contact angle measurements are commonly used to ensure process quality.

A wetting agent is a surface-active molecule used to reduce the surface tension of water. Water’s high surface tension is problematic in applications where it must spread or penetrate, such as in formulations of coatings, detergents, etc. What are the effects of wetting agents on surfaces, and how can they be quantified?

Advancing and Receding Contact Angle

When discussing contact angles, people are typically referring to the angle that is measured when a droplet is sitting on a surface, or a static contact angle. But why has the drop taken that shape? Is that the only possible contact angle on that surface, or could other angles be measured as well? Which is the correct one?

When water hits a surface, it can behave in several different ways. Depending on the shape of the drop and the angle that the drop creates as it sits on the surface, the material is deemed either hydrophilic or hydrophobic. When are hydrophilic surface properties advantageous, and what are the implications in different applications ranging from biomedical devices to marine engineering?

Contact angles demonstrating hydrophobic and hydrophilic surfaces

Fogging happens when a water vapor present in the air comes in contact with the surface that is colder than the dew point of the surrounding air-water vapor mixture. How can making surfaces superhydrophobic or superhydrophilic achieve anti-fogging properties, and how can contact angle measurements be used to study both of these strategies?

Efficient quality control for electronics manufacturing

Manufacturing electronics requires adhering multiple materials together with the goal of achieving permanent, or temporary adhesion, differing for each step in the process. Contact angle measurements can provide important information about surface properties that determine how good the adhesion will be between them.

Printed circuit boards, or PCBs for short, are essential parts of all electronic devices. One of the main challenges in PCB manufacturing is the adhesion of the conformal coating, which requires a properly cleaned surface. Of all the methods to test for cleanliness, contact angle measurement is the easiest and most efficient.

Good adhesion is important in many steps of electronic manufacturing. One of the most critical steps is the application of the photoresist, which must result in proper adhesion for a successful lithographic process. Loss of adhesion in the development or etching process will result in patterning errors, negatively affecting the device.

Improved control and design of medical implants through simultaneous characterization of topography and contact angle

To ensure the safety and quality of medical implants, parameters such as the roughness, cleanliness, and wettability of the surface must be characterized. Because these properties are all coupled to some degree (for example, roughness may enhance the hydrophobic or hydrophilic effects of a surface), it may be insufficient to simply take a single value, such as the contact angle, to fully understand the state of the surface.

By combining a topographical measurement with the contact angle, the corrected contact angle and surface energy can be obtained. These values can then be used to determine not only whether the roughness treatment has yielded the desired result, but also whether the surface is free of contaminants. The video below explains how the Theta Flow can support simultaneous contact angle and surface roughness measurements, and what valuable data can be obtained from these experiments.

For a deeper look into why these measurements are important for biomedical implant design, and the scientific theories that support these assertions, read this application note.

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