Wolfgang Sigmund

Repels Dirt, Dust, Water, and Even Oily Liquids and Organic Solvents

When formulated into paint, these silica or titanium dioxide composite particles make the coating superhydrophobic. Paint on furniture and the exterior and interior walls of buildings accumulate dirt, dust, air pollution, and other contaminant particles . Painted areas, therefore, need to be cleaned or repainted. Several available hydrophobic paints can repel water. However, no available water based paint is superhydrophobic, repelling water, oil, dirt, and other contaminants.

Researchers at the University of Florida have developed a process for coating silicon and titanium dioxide particles so that when they are included in aqueous paint formulations, they make the paint superhydrophobic. The paint leaves surfaces with a contact angle greater than 150 degrees, such that liquid droplets will barely contact the painted surface, making it self-cleaning. The painted surface will cause water droplets, oily liquids, and organic solvents to roll off the surface along with dirt, dust, and air pollution particles. Furthermore, this is the first paint that is free of volatile organic compounds.

Application

Superhydrophobic paints and coatings that make interior and exterior surfaces self-cleaning while being free of volatile organic compounds

Advantages

• Aqueous version of superhydrophobic paint, making indoor and outdoor painting possible without volatile organic compounds
• Surface contact angle greater than 150°, keeping water and oil from seeping into the painted or coated surface
• Causes contaminants to accumulate and roll off, making a painted surface self-cleaning
• Superhydrophobic resistance to wetting, enhancing industrial paints and coatings

Technology

Newly formulated Odin particles consist of a finely tuned inner core such as silicon dioxide or titanium dioxide and a tailored hydrophobic outer layer. The combination of hydrophilic inside and hydrophobic outside gives these dichotomous particles the ability to disperse in water or other aqueous media and remain dispersed while the medium is wet, then leave behind a superlyophobic layer when the medium dries. This enables their formulation into a superhydrophobic paint that, when dried, makes surfaces difficult to wet, having a water droplet contact angle greater than 150° and roll off angle less than 2°.

Dichotomous Hydrophilic/Hydrophobic Particles Generate Surfaces with Contact Angle Greater than 150° to Repel Liquids and Oils

These particles with hydrophilic cores and hydrophobic agents around them disperse in water to form a coating that generates a superhydrophobic, superoleophobic, or omniphobic surface upon application. Interior and exterior surfaces such as countertops and coatings on furniture can have water, oil, and other liquids seep into them, potentially staining the surfaces permanently . All surfaces that need to be coated or painted will benefit from this composition. Available coatings or water-based paints are incapable of generating superhydrophobic, superoleophobic, or omniphobic surfaces desirable for many applications since processing aids are needed to make them compatible with water, which render them hydrophilic after drying.

Researchers at the University of Florida have developed composite hydrophilic-hydrophobic particles that disperse in water, creating a superhydrophobic, superoleophobic, or omniphobic surface coating on drying. The superhydrophobic, superoleophobic, and omniphobic surfaces will be easy to clean because droplets of water, oil, and other liquids will not seep into them. Coated surfaces have a contact angle greater than 150°, repelling almost all liquid droplets. Droplets will collect contaminants such as dust and dirt while rolling off the surface, making it self-cleaning.

Application

Superhydrophobic, superoleophobic, or omniphobic surfaces that self-clean when water, oil, and all other liquids get on the surface

Advantages

• Water based composition that can be used indoors and with strict VOC (volatile organic compounds) requirements since there are no VOC used in this paint
• Repels liquid droplets that pick up contaminants such as dust, dirt, and air pollution, enabling the coated surface to self-clean
• Gives surfaces contact angles greater than 150°, preventing water, oil, and all other liquids from seeping into the painted or coated surface
• Enables production of superhydrophobic, superoleophobic, and omniphobic paints and coatings, benefitting many industries

Technology

In these composite particles, the combination of two features, hydrophilicity at the core and hydrophobicity on the outside, makes the particles both dispersible in water and able to leave a superhydrophobic, superoleophobic, or omniphobic coating on a surface on drying. The hydrophilic core particle has smaller, silicone-based hydrophobic particles bonded around it. The composite particles can disperse in water-based paints or coatings under certain conditions, and upon application to a surface and drying, can coat surfaces, making them superhydrophobic, superoleophobic, or omniphobic. The surface is highly hydrophobic and difficult to wet, having a water droplet contact angle greater than 150° and roll off angle less than 2°. The surface is also highly oleophobic, difficult to wet with oil, and highly omniphobic, difficult for solids to stick to the surface.

Safely and Rapidly Fabricates Mechanically Sound, Freeform Structures

This non-toxic, 3D printing material and technique rapidly builds mechanically sound ceramic and metallic structures by curing layers of non-toxic slurry with a laser or infrared lamp. The market for ceramic 3D printing was $116 million in 2020 and should grow to $384 million by 2025. The market for metallic 3D printing should reach $3.159 billion by 2024. Current ceramic and metallic 3D printing processes rely on the use of toxic compounds to form printable slurries, creating worker safety hazards and limiting the environments where ceramic and metallic 3D printing can be done.

Researchers at the University of Florida have developed a non-toxic, 3D printing material and technique that enables the rapid fabrication of mechanically sound ceramic or metallic structures without the safety hazards associated with current ceramic and metallic 3D printing methods.

Application

3D printing of mechanically sound ceramic and metallic structures from a non-toxic slurry that is cured with a laser or infrared lamp

Advantages

• Uses non-toxic slurry components prepared in water, eliminating the need for safety protocols for handling toxic materials and enabling safe ceramic and metallic 3D printing in more environments
• Employs the constant volume technique, preventing finished material shrinkage and allowing for the curing of large two-dimensional structures
• Remaining uncured slurry can be poured off and reused, reducing waste and lowering machining costs

Technology

A slurry consisting of non-toxic, water-soluble proteins and metallic or ceramic powders is spread in a thin layer and cured with a laser or infrared lamp with a photomask to produce a 2D structure with the desired dimensions. After building layers of cured material on top of each other, the remaining, un-cured slurry can be poured off and reused. Once the resulting 3D structure dries, it is stable for handling and considered mechanically sound.

Alumina Nanoparticle Spray Helps Surfaces Repel Water, Oil, Dirt, and Corrosives

This easily applied, highly transparent, superhydrophobic and superoleophobic coating makes glass and paint and a variety of surfaces self-cleaning. Several products on the market claim to repel water; this spray achieves superhydrophobicity and superoleophobicity, repelling water, oil, and dirt so that surfaces stay clean. University of Florida researchers have developed a highly hydrophobic alumina nanoparticle spray, easy to apply even to large areas, that causes water droplets to bounce from surfaces on contact, leaving them completely dry. The coating is anti-corrosive and anti-icing and can be used to protect important machinery such as circuits and grids or added into paints or countertop substrates to repel water, oily liquids, and organic solvents. By using surface physics not surface chemistry, scientists can vary the thickness of the alumina coating to best suit the material being repelled. A coating of 200-300 nanometers repels water, is highly transparent, and can be applied to surfaces that require high visibility, such as windshields, architectural glass, and device displays, to keep them clean. When a coating thickness of 1-100 micrometers is applied, the resulting surface is opaque and both superhydrophobic and superoleophobic.

Application

Superhydrophobic and superoleophobic alumina coating for glass and other surfaces

Advantages

• Coating repels water and oil, creating easy-to-clean surfaces
• Applies by spraying, making it easy to cover large areas quickly
• Transparent, offering high visibility when applied to windshields, windows and device displays
• Can be added to paint, making paint repel oil, dirt and water

Technology

The spray-on coating -- containing hydrophobic alumina nanoparticles -- gives surfaces a contact angle of 150 degrees so that water or oily droplets bounce off immediately, leaving the surface dry and clean. When added to paint or other substrates, those substances become superhydrophobic and superoleophobic. When coated with the spray, glass remains highly transparent with visible transmittance reaching as high as 90 percent. Though applications include water repellent windshields, easy-cleaning windows, or easy-cleaning device displays, the spray can be used on numerous substrates to make them water and oil repellent. The spray is fairly easily used for a large area application.

Exhibits Higher Rates of Superhydrophobicity than Paints Without Added Color Pigments

This durable colored paint supplies superhydrophobic and self-cleaning properties to a variety of surfaces. A material exhibits hydrophobic properties when its surface is difficult to wet due to the organization of its particles. This resistance to wetness brings about properties such as self-cleaning and resistance to bacteria buildup. All hydrophobic paints on the market are available only in white because of the disruptive chemical composition of the pigments that give paints color. Researchers at the University of Florida have developed a superhydophobic paint that is colored and exhibits even higher rates of superhydrophobicity than those without the added color pigments. This paint can be applied to various surfaces for architectural, household, medical, and other usages.

Application

Durable colored paint gives surfaces superhydrophobic and antimicrobial properties

Advantages

• Overcomes disruptive chemical composition of pigments, resulting in superhydrophobic paints with color
• Applies superhydrophobic properties to surfaces, making them easy to clean and resistant to bacteria

Technology

This durable colored paint exhibits superhydrophobic properties due to the arrangement of its silica nanoparticles. These nanoparticles in the composition of the paint create water contact angles of over 150 degrees, which mimic the water resistant properties of lotus leaves. The silica nanoparticle organization encourages bacteria resistance due to the resulting superhydrophobicity of the paint. This paint incorporates blue, red, and green pigments. The paints which contain these coloring pigments exhibit higher rates of water resistance than standard white superhydrophobic paints due to the chemical composition of the pigments.

Silica Nanoparticles Applied to Substrate Surface Gives Superhydrophobic Properties

This transparent, durable ceramic coating can be applied to surfaces to supply superhydrophobic and self-cleaning properties. Superhydrophobic surfaces are those that have a water contact angle larger than 150 degrees. These types of surfaces, modeled after lotus plants, prevent liquid droplets from absorbing energy which prevents adhesion. Existing superhydrophobic coatings either need extreme processing conditions or have not been tested for durability and transparency. Researchers at the University of Florida have developed a superhydrophobic ceramic coating composed of silica nanoparticles that is transparent and durable and can be processed at room temperature. Superhydrophobic surfaces have many applications, such as in high voltage systems, microelectromechanical systems, and for anticorrosion of metal coatings. Other possible uses could be in biomedical applications or in photovoltaic devices.

Application

Ceramic coating gives surfaces superhydrophobic properties while remaining transparent and durable

Advantages

• Repels water and some other liquids, creating easy-to-clean surfaces
• Remains transparent, offering high visibility when applied to windshields, windows, and device displays
• Reduces rate of metal corrosion, increasing longevity of structures such as bridges
• Functions in extreme temperatures, extending performance of structures in snow, ice, or rain

Technology

This transparent, durable, superhydrophobic ceramic coating is created by randomly stacking silica nanoparticles on a surface to create a rough topography. The silica nanoparticles are sufficiently small, so most light transmits through the coating. The silica is then infused with a sol-gel glass matrix to ensure that the rough topography is retained. After curing, the surface is coated with a fluorinating agent to form a self-assembled monolayer. Controlling the particle size, stacking structure, and coating allows formation of a ceramic coating that is transparent and durable. The coating gives surfaces a contact angle of 150 degrees so water droplets cannot rest on the surface. The coating was tested to determine the transmittance and durability of the technology.

Wear-Resistant Coating Repels Water and Oil, Making Surfaces Truly Self-Cleaning

This surface treatment far exceeds the durability of available self-cleaning superhydrophobic and oleophobic coatings, increasing the lifetime of the coating and providing a significant marketing advantage. This water and oil repellent coating could be applied to surfaces requiring self-cleaning and wear-resistant properties such as anti-fingerprint coatings for touch-screens and windows. In 2015, tablet sales will surpass sales of personal computers for the first time and more than 2 billion people worldwide will use a smartphone , creating an increasing need for durable surfaces that repel water and oil. This lucrative solution is applicable to many platforms. Available surface treatments have yet to overcome the degradation of the coatings observed in everyday use, which severely limits product use lifetimes. University of Florida researchers use thermoset-thermoplastic composites with multiple reentrant surface topography to render surfaces superhydrophobic and oleophobic, a significant improvement in durability to plastron technology. The goal of this surface treatment is to provide a wear-resistant surface coating that doesn’t lose its shape or functionality when exposed to environmental conditions over time.

Application

Durable superhydrophobic and oleophobic coating for self-cleaning surfaces

Advantages

• Repels oils and water, making the treatment ideal for touch-screens and self-cleaning surfaces
• Maintains durable properties and functionality, outpacing available surface coatings

Technology

This surface coating is an improvement over previous methods of hairy plastron technology. The method of preparing the surface treatment includes providing a membrane with pores, providing a polymeric precursor that is forced into the membrane and the pores, cured, and then separated to form a superhydrophobic surface. By adding a perfluorinated coating to the polymeric network, the surface becomes superoleophobic in addition to being superhydrophobic.

Liquid Solution Is Easily Applied to Make a Variety of Substrates Repel Water, Oil, and Dirt

When applied to a surface, this ceramic-polymer composite results in articles with more durable superhydrophobic and oleophobic coatings. Surface cleaning and repainting of buildings, vehicles and energy collection devices can be costly and time consuming. For example, the average American has to repaint his or her house every five to six years and spends thousands of dollars doing so; it is easy to see the advantage in using a coating that repels dirt, oil, and water. Available surface coatings are water repellent and some even repel oil, but no superhydrophobic and oleophobic surface can be produced easily on substrates nor do they display sufficient performance and durability. Researchers at the University of Florida, however, have developed a new type of surface coating that is easily applied, addresses durability and performance issues of available products, and makes surfaces both superhydrophobic and oleophobic. This solution can be applied to various substrates to render them both water and oil repellent.

Application:

A ceramic-polymer composite that makes surfaces superhydrophoic and oleophobic

Advantages:

• Applies multiple principles to repel water and oil, making coated surfaces virtually self-cleaning
• Surpasses quality of available coatings, improving durability and performance of superhydrophobic and oleophobic effects
• Combination of plastron and “lotus leaf” effect produces dynamic response, lowering quantity of particles required and associated production costs

Technology:

A surface with an inherent repellency of water, oil, and dirt is governed by surface-energy parameters between the surface and the contacting liquid or solid. Where the sum of free surface energies is low, adhesion is weak. Teflon’s non-stick surface is an example of this. When principles apparent in nature and science -- such as van der Waals forces, the "lotus effect," the plastron effect, and the Cassie-Baxter state -- are applied, surfaces effectively repel dirt, water, and oil, making them virtually self-cleaning. With this coating, all of those principles are in force. Whether directly applied to an article or included in paint or other materials, when the applied coating reaches its final in-use state, the surface will be superhydrophobic and oleophobic; water and oil droplets will roll off instead of adhering to the surface, taking any dirt with them.