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ramé-hart
Newsletter
April 2023 |
| What does AI know about surface science? |
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We often reach out to experts in the field of wetting, contact angle and surface science for guidance with problems that are beyond our capacity to solve. It's refreshing to encounter people whose experience and knowledge make them an expert on a subject. This month we conducted an interview with a non-person AI bot on the topic of surface science. We found the interview to be most fascinating and informative and thus we feel compelled to share it with you now for your edification: Carl: What is contact angle? ChatGPT: Contact angle is a measure of the wettability of a solid surface by a liquid. It refers to the angle formed by the liquid at the three-phase boundary where the solid surface, liquid, and gas or vapor phases meet. The contact angle is typically measured in degrees and can range from 0 degrees to 180 degrees. The contact angle is influenced by the properties of the solid surface, the liquid, and the ambient conditions such as temperature and pressure. A liquid with a low contact angle (less than 90 degrees) is said to be wetting the solid surface, while a liquid with a high contact angle (greater than 90 degrees) is said to be non-wetting or partially wetting the surface. The contact angle can be used to characterize the surface properties of materials and to study the interactions between liquids and solid surfaces. It is important in many industrial applications, including coating and printing processes, adhesion, and surface cleaning. Carl: How is contact angle measured? ChatGPT: Contact angle can be measured using a variety of methods, including the sessile drop method, the captive bubble method, and the Wilhelmy plate method. The most commonly used method is the sessile drop method, which involves placing a droplet of liquid on a solid surface and measuring the angle formed at the three-phase boundary where the solid, liquid, and gas or vapor phases meet. To measure contact angle using the sessile drop method, a small droplet of liquid is placed onto the surface of interest using a microsyringe or pipette. The droplet is allowed to equilibrate for several seconds, during which time it will spread and form a characteristic shape. A digital camera or microscope is then used to capture an image of the droplet and the angle formed at the three-phase boundary is measured using image analysis software. The angle measurement can be affected by a number of factors, including the roughness, chemistry, and topography of the solid surface, as well as the properties of the liquid and environmental factors such as temperature and humidity. Careful control of these variables is necessary to obtain accurate and reproducible measurements of contact angle. Other methods, such as the captive bubble method and the Wilhelmy plate method, involve measuring the force required to detach a liquid droplet or bubble from a surface, and can be used to measure contact angle indirectly. Carl: What is contact angle hysteresis? ChatGPT: Contact angle hysteresis refers to the difference in contact angle measured during the advancing and receding stages of a liquid droplet as it is placed on and removed from a solid surface. In other words, it refers to the difference between the contact angle when a droplet is spreading on a surface (advancing contact angle) and the contact angle when a droplet is contracting from the surface (receding contact angle). Contact angle hysteresis occurs due to the presence of surface roughness, chemical heterogeneity, or other factors that can affect the interactions between the liquid and solid surface. These factors can cause the contact angle to be different depending on whether the droplet is advancing or receding on the surface. Contact angle hysteresis is an important factor in many practical applications, including surface coatings, adhesion, and microfluidic systems. It can affect the behavior of liquid droplets on surfaces, such as their ability to wet or spread, and can have implications for the performance of devices and materials that rely on surface interactions. Carl: What is surface energy? ChatGPT: Surface energy is a measure of the amount of energy required to create or change the surface area of a material. It arises due to the unbalanced intermolecular forces at the surface of a material, which result in a higher energy state than the bulk material. The surface energy of a material can be calculated as the work required to create a unit of new surface area, and is typically measured in units of joules per square meter (J/m^2) or dynes per centimeter (dyn/cm). The surface energy of a material plays an important role in many physical and chemical processes, including wetting and adhesion. A material with a high surface energy tends to be more wettable and more easily wet by liquids, while a material with a low surface energy tends to be less wettable and repels liquids. Surface energy can be modified through various techniques, including surface treatments such as plasma treatment, chemical modification, and the deposition of coatings. These techniques can be used to control the wetting and adhesion properties of a material and are important in many industrial applications such as printing, coating, and adhesion. Carl: What is surface tension? ChatGPT: Surface tension is the property of a liquid that causes it to resist external forces that would otherwise deform or break its surface. It arises due to the cohesive forces between molecules in the liquid, which are stronger than the adhesive forces between the liquid and its surroundings. At the interface between the liquid and air or another immiscible liquid, the cohesive forces cause the liquid molecules to be more strongly attracted to each other than to the surrounding medium. This results in the formation of a surface layer or film that is under tension and tends to contract to the smallest possible surface area. The surface tension of a liquid can be measured in units of force per unit length, such as newtons per meter or dynes per centimeter. Surface tension plays an important role in a wide range of phenomena, including the formation of droplets, bubbles, and menisci, capillary rise and depression in narrow tubes or pores, wetting and spreading of liquids on solid surfaces, and many biological processes such as the movement of fluids in plants and animals. It is also a key factor in many industrial processes such as printing, coating, and emulsion formation. Carl: What is an ideal surface? ChatGPT: An ideal surface is a surface that has perfect properties for a specific application. For example, an ideal surface for a non-stick cooking pan would be one that is hydrophobic, i.e. repels water and other liquids, and is also oleophobic, i.e. repels oils and other greasy substances. An ideal surface for a solar cell would be one that is highly transparent and also has a high charge carrier mobility, allowing for efficient conversion of sunlight into electricity. In practice, it is difficult to achieve an ideal surface, as real-world surfaces are often subject to a wide range of environmental factors and may be affected by imperfections, roughness, and other properties that can influence their performance. However, engineers and scientists strive to create surfaces that come as close as possible to the ideal for a given application, using a variety of surface engineering techniques and materials. In many cases, an ideal surface may also depend on the specific requirements and constraints of a given application, and trade-offs may need to be made between different surface properties to optimize overall performance. For example, a surface that is highly hydrophobic may be ideal for a non-stick pan, but may not be desirable for a biomedical device that needs to promote cell adhesion and growth. Carl: What is superhydrophobicity? ChatGPT: Superhydrophobicity is a surface property in which a surface exhibits extreme water repellency, such that water droplets bead up and roll off the surface very easily. A superhydrophobic surface has a high contact angle (>150 degrees) and a low contact angle hysteresis, meaning that the contact angle remains stable even when the droplet is moving or tilted. Superhydrophobicity is often achieved by creating a surface that has a combination of low surface energy and high surface roughness. The roughness on the surface can be at the micro or nanoscale, and can be created by a variety of methods including etching, coating deposition, and surface patterning. Superhydrophobic surfaces have a wide range of potential applications, including self-cleaning surfaces, anti-icing coatings, and water-repellent textiles. They are also of interest for their potential use in drag reduction and flow control in fluid dynamics, as the water repellency can reduce the drag force on a surface and improve the efficiency of fluid flow. Carl: What is superhydrophilicity? ChatGPT: Superhydrophilicity is a surface property in which a surface exhibits extreme water affinity, such that water spreads out and wets the surface very easily. A superhydrophilic surface has a contact angle of close to 0 degrees, meaning that water spreads out and covers the surface completely. Superhydrophilicity can be achieved by creating a surface that has a high surface energy and is free of hydrophobic materials. This can be done by modifying the surface chemistry through chemical treatments, plasma treatments, or deposition of hydrophilic coatings. Superhydrophilic surfaces have a range of potential applications, including anti-fog coatings, anti-fouling surfaces, and self-cleaning materials. They are also of interest in applications where efficient transport of liquids is important, such as in microfluidic devices or fuel cells, where superhydrophilic channels can enhance the flow of liquids through the device. Carl: What is electrowetting? ChatGPT: Electrowetting is a phenomenon in which the wetting behavior of a liquid on a solid surface can be modified by applying an electric field. In electrowetting, the contact angle between the liquid and the solid surface can be controlled by varying the voltage applied to an electrode located beneath the surface. The basic principle behind electrowetting is that the applied electric field induces an electrostatic force that changes the balance between the interfacial tension of the liquid and the adhesion force between the liquid and the solid surface. This leads to a change in the wetting behavior of the liquid, with the contact angle decreasing as the voltage is increased. Electrowetting has a range of potential applications in fields such as microfluidics, displays, and optics. In microfluidic devices, for example, electrowetting can be used to manipulate small volumes of liquid and to control the movement of droplets within the device. In displays and optics, electrowetting can be used to create tunable lenses, which can change their focal length in response to an applied voltage. Carl: What does ramé-hart instrument company in NJ sell? ChatGPT: ramé-hart instrument company, based in Succasunna, NJ, is a manufacturer of contact angle goniometers and tensiometers, which are used to measure the surface tension and contact angle of liquids on solid surfaces. They also provide related accessories, software, and services for these instruments. These instruments are used in a variety of industries including pharmaceuticals, coatings, adhesives, electronics, and more. Carl: Write a poem about measuring contact angle using a ramé-hart goniometer. ChatGPT: A droplet on a
surface, oh so small, The ramé-hart
Goniometer is the go-to, From hydrophobic to
hydrophilic, Oh, ramé-hart
Goniometer, how we rely on thee, Carl: But if it's contact
angle you want to measure, |
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Regards,
Carl Clegg |
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