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ramé-hart
Newsletter
February 2025 |
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| Slippery versus Sticky Surfaces | |||||||||||||||||||||
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In the surface science world, the
study of wetting behaviors is important in many applications - from
industrial coatings to biological interfaces. A key area of interest
within this field is understanding the difference between slippery
and sticky surfaces, each with unique interactions with liquids.
Understanding these differences is critical for researchers aiming
to manipulate wetting properties for specific applications and
purposes.
Slippery Surfaces Definition and Characteristics: Slippery surfaces are designed to minimize the adhesion of liquids, allowing them to move or slide off effortlessly. These surfaces exhibit extremely low friction and promote high liquid mobility, resulting in reduced contact time between the liquid and the surface. Mechanisms: 1. Superhydrophobicity: Achieved through the combination of low surface energy materials and micro- or nanoscale roughness. Water contact angles on such surfaces typically exceed 150°, and the contact angle hysteresis is minimal, allowing water droplets to bead up and roll off easily. Additionally, the roll-off angle will be very low. This effect is famously observed in the lotus leaf, known as the "Lotus Effect." The ramé-hart Model 290 is a popular choice for researchers who are developing and studying superhydrophobic surfaces as this setup includes both the Automated Tilting Base for capturing roll-off angle and contact angle hysteresis as well as the Automated Dispensing System and DROPimage Advanced software.
2. SLIPS (Slippery Liquid-Infused Porous Surfaces): This innovative technology involves infusing a porous structure with a lubricating liquid, creating a smooth and continuous interface. SLIPS can repel a wide range of liquids, including oils and organic solvents, enhancing their utility in various environments.1 Applications:
Advantages:
Sticky Surfaces Definition and Characteristics: Sticky surfaces, in contrast, are engineered to enhance the adhesion of liquids or other materials. These surfaces promote liquid spreading and strong adherence, often resulting in high contact angle hysteresis, low contact angles, and high roll-off angles. Mechanisms: 1. High Surface Energy: Surfaces with high surface energy tend to attract liquids, leading to increased wettability and lower contact angles. Hydrophilic surfaces, for example, exhibit strong interactions with water, causing it to spread rather than bead. 2. Surface Texturing: Certain textures can increase the contact area between the liquid and the surface, enhancing adhesion. Unlike slippery surfaces, the roughness here promotes liquid retention rather than repellence. The key difference is that sticky surfaces are typically in a Wenzel state while slippery surfaces (particularly superhydrophobic surfaces) are in a Cassie state.2 Imagine it this way: think of a toasted English muffin with all its nooks and crannies, but shrunk down to a nanoscopic scale. Now, if a drop of liquid is placed on this textured surface and doesn’t seep into the nooks and crannies but instead sits on top, this is a Cassie state. In this state, the liquid forms a large contact angle, and there’s minimal contact between the drop and the surface, leading to increased mobility and "slipperiness." Conversely, if the drop sinks into all the nooks and crannies (a Wenzel state), the overall surface area in contact with the drop is much greater, pinning the drop to the surface and making it very sticky. Applications:
Advantages:
Comparative Analysis
ConclusionThe differentiation between slippery and sticky surfaces is fundamental in wetting behavior research. Slippery surfaces are optimal for applications requiring minimal liquid adhesion and easy cleaning, while sticky surfaces are ideal for scenarios necessitating strong liquid retention and spreading. By manipulating surface energy, texture, and chemistry, researchers can tailor surfaces to meet the specific demands of their applications. Understanding these mechanisms not only enhances the design of functional materials but also broadens the scope of innovative applications in industries ranging from healthcare to environmental management. Notes |
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| Product of the Month - Model 290 | |||||||||||||||||||||
| This month's featured product is the Model 290, prominently mentioned and pictured in the article above. A perennial top-seller, the Model 290 is renowned for its versatile capabilities. It easily measures contact angle, surface energy, and surface tension. With the tilting base method or the add/remove volume method using the Automated Dispensing System, you can capture advancing and receding contact angles and the contact angle hysteresis. It also allows for interfacial tension and roll-off angle measurements. Enhance its functionality with our Oscillator to assess surface dilatational elasticity and viscosity. The Model 290 supports a range of modular accessories for temperature-controlled studies, captive bubble measurements, and experiments with films or wafers. As a true Swiss-army knife of precision, it is meticulously engineered, hand-crafted, and assembled to meet the highest quality standards. Contact us today for a no-obligation quotation for our Model 290. | |||||||||||||||||||||
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Regards,
Carl Clegg |
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