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ramé-hart Newsletter


October 2023

Laws you need to know for contact angle
Contact angle, a fundamental concept in surface science and interfacial chemistry, is governed by several scientific laws and principles that help describe and understand the behavior of liquids on solid surfaces. Here is a list of some key scientific laws and principles related to contact angle:

1. Young-Laplace Equation: This equation relates the contact angle (θ), the interfacial tension between the liquid, solid, and vapor phases (γ), and the radii of curvature of the liquid-vapor interface (R1) and the liquid-solid interface (R2):

γ(liquid-vapor) * (cos θ) = γ(liquid-solid) * [1/R1 - 1/R2]

It describes the balance of forces at the three-phase contact line.

2. Young's Equation: Young's equation relates the contact angle (θ), the interfacial tensions (γ) between the solid-liquid, liquid-vapor, and solid-vapor interfaces:

γ(liquid-solid) * (cos θ) = γ(liquid-vapor) - γ(solid-vapor)

Young's equation is fundamental in understanding how surface tension and wetting properties influence contact angles and is the most important law relating to contact angle.

3. Wenzel's Equation: Wenzel's equation describes how the roughness of a solid surface affects the apparent contact angle (θ*) of a liquid on that surface. It relates the actual contact area (A) to the projected area (A0) due to roughness:

cos θ* = r * cos θ

Here, r represents the roughness factor (A/A0), and θ* is the apparent contact angle.

4. Cassie-Baxter Equation: The Cassie-Baxter equation describes the wetting behavior of a liquid droplet on a composite surface with varying wetting properties. It relates the contact angle on the composite surface (θ_cb) to the fractional coverage (f) of two different solid components with different contact angles (θ1 and θ2):

cos θ_cb = f * cos θ1 + (1 - f) * cos θ2

It explains how the overall contact angle is influenced by the surface composition.

5. Dupré's Law: Dupré's law states that the work of adhesion (W_ad) between a liquid and a solid surface is equal to the sum of the interfacial energies of the solid-liquid (γ(sl)) and solid-vapor (γ(sv)) interfaces:

W_ad = γ(sl) + γ(sv)

It is relevant for understanding the thermodynamics of wetting and contact angle behavior.

These scientific laws and equations provide a foundation for understanding and predicting contact angles, which are crucial in various fields, including materials science, chemistry, and biology, where surface interactions play a significant role.

Why ramé-hart?

This month we did some updating on our website. What follows is a new section on the "Why ramé-hart?" page.

In the world of surface science and interfacial analysis, precision and reliability are critically important. Researchers, engineers, and scientists across various industries rely on instruments that can accurately measure contact angles, surface tension, surface energy, and other interfacial properties.

One company that has consistently delivered state-of-the-art goniometer and tensiometer instruments, ensuring longevity and reliability, is the ramé-hart instrument co. Since 1961 ramé-hart has been at the forefront of developing cutting-edge instruments that serve a wide range of applications, from materials science to pharmaceuticals.

ramé-hart's enduring success can be attributed to its unwavering commitment to quality. They revere the highest standards in product design, manufacturing, and customer support. ramé-hart's instruments are precision-engineered and hand-built with meticulous attention to detail, ensuring consistent and reliable performance for many years.

One of the hallmarks of ramé-hart is their incorporation of state-of-the-art technology. The company continuously invests in research and development to stay ahead of the curve, offering innovative solutions to meet the evolving needs of its customers. A SuperSpeed digital camera that operates at 540 fps and is now standard on all models above Model 90 is an example of that. Their goniometer and tensiometer instruments feature advanced DROPimage software packages which provide intuitive control and data analysis. Whether you're measuring contact angles, surface tension, or interfacial properties, ramé-hart's instruments offer unparalleled accuracy and repeatability, making them indispensable tools for researchers and engineers alike.

ramé-hart's instruments have found applications in a wide array of industries. From aerospace to pharmaceuticals, their goniometers and tensiometers are trusted by professionals across the globe - in both academic and commercial environments. Whether you're analyzing the wettability of a new composite material or studying the surface tension of pharmaceutical formulations, ramé-hart's instruments can adapt to your specific requirements.

Investing in high-quality laboratory instruments is not only about meeting your immediate research needs but also about ensuring long-term reliability. ramé-hart's instruments are built to last, with rugged designs and rigorous quality control processes. This longevity is not only cost-effective but also environmentally friendly, reducing the need for frequent replacements and minimizing waste. ramé-hart has customers who are still using Model 100 instruments that were built 30, 40, and 50 years ago. An array of available imaging upgrade kits further extends the life of older instruments by modernizing their imaging subsystems, software, and computer. 

ramé-hart's commitment to excellence extends beyond its instruments. The company is known for its outstanding customer support and technical assistance. Whether you have questions about instrument operation, need help with data analysis, or require other service, ramé-hart's dedicated team is always ready to assist you.

Recognizing that every research project and application is unique, ramé-hart offers a range of customization options for its goniometer and tensiometer instruments. Whether it's adapting an existing instrument or developing a custom solution, ramé-hart works closely with its customers to meet their specific needs. For researchers, scientists, and engineers who demand precision, reliability, and longevity in their goniometer and tensiometer instruments, ramé-hart instrument co. stands as a trusted partner. With a legacy spanning over six decades, ramé-hart has consistently delivered state-of-the-art solutions that perform for many years, making them an indispensable asset in laboratories and research facilities around the world. By choosing ramé-hart as your partner, you gain access to cutting-edge technology, outstanding customer support, and the peace of mind that comes with investing in instruments built to last. Whether you're in academia, industry, or research, ramé-hart's commitment to quality ensures that your interfacial analysis needs are met with precision and excellence, today and for many years to come.


Carl Clegg
Director of Sales
Phone 973-448-0305
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