Are lotus leaves hydrophobic or hydrophilic?
This work shows that the lotus leaves can be either hydrophobic or hydrophilic, depending on how the water gets on to their surfaces. This finding has significant ramifications on how to make and use superhydrophobic surfaces. you can request a copy directly from the authors. ...
How does the lotus leaf protect itself from water?
When water droplets are applied to the lotus leaf, they sit lightly on the tips of the hydrophobic protrusions as if on a bed of nails (see Figure 2). This combined structure traps a layer of air in between the surface of the leaf and the water droplet. Hence, the water is not allowed to wet the surface and is easily displaced (see Figure 3).
What is the wettability of lotus leaf?
The lotus leaf has the Janus wettability and outstanding floatability at multiphase interface. The ingenious design on lotus leaf surfaces enlightens us to fabricate the superhydrophobic/superhydrophilic binary cooperative membrane.
What is the rough structure of the lotus leaf?
Lesson Background and Concepts for Teachers. Scientists have found that the basis for both of these properties (self-cleaning and water-repellent) lies in the rough structure of the surface of the lotus leaves. The lotus leaf has a series of protrusions on the order of 10 μm (1.0 x 10 - 5 m) high covering its surface.
Why are lotus leaves superhydrophobic?
When rain falls on lotus leaves, water beads up with a contact angle in the superhydrophobic range of about 160°. The water drops promptly roll off the leaves collecting dirt along the way. This behavior, known as the Lotus Effect,1,2.
Are lotuses hydrophobic?
The waxy material on the surface of lotus leaves is hydrophobic.
Is that true that lotus leaf is hydrophobic?
The epidermis of the lotus plant possesses papillae 10 μm to 20 μm in height and 10 μm to 15 μm in width on which the so-called epicuticular waxes are imposed. These superimposed waxes are hydrophobic and form the second layer of the double structure.
Why leaves of lotus are broad?
1 Answer. The leaves of the lotus plants are broad to give support to the lotus flower to float on the water.
Are dried lotus leaves hydrophobic?
If the contact angle of water drop on solid surface is greater than 150 °, it is called super hydrophobic surface [5], lotus leaves are super hydrophobic. plants. The superhydrophobic mechanism and the similarities and differences of lotus leaf, rice and nasturtium are not reported.
How are lotus leaves waterproof?
In summary, the structure of a lotus leaf has a clever design that discourages surface wetting both through a waxy nonpolar coating and a rough structure which both make surface interactions less favorable, allowing water to bead up into spheres and easily roll off the leaf.
What plants are hydrophobic?
Surfaces that repel water, like the leaves of the Colocasia plant, are called hydrophobic.
What is superhydrophobic surface?
Ultrahydrophobic (or superhydrophobic) surfaces are highly hydrophobic, i.e., extremely difficult to wet. The contact angles of a water droplet on an ultrahydrophobic material exceed 150°. This is also referred to as the lotus effect, after the superhydrophobic leaves of the lotus plant.
What are hydrophobic materials?
Hydrophobic materials are known as non-polar materials with a low affinity to water, which makes them water repelling. A contact angle of less than 90° indicates hydrophilic interaction where as an angle greater than 90° indicates a hydrophobic interaction.
What type of leaf does lotus have?
Description : Lotus is the water plant. It has broad floating leaves and bright fragrant flowers. The leaves and flowers float and have long stems that contain air spaces. It has many petals overlapping in the symmetrical pattern.
Which plants have broad leaves?
Most deciduous trees are broad-leaved but some are coniferous, like larches....Tree types.Gymnosperms (seed plants not flowering)Angiosperms (flowering seed plants)Needle-like or scale-like leavesBroad leavesExamples: firs, spruces, pinesExamples: hickories, maples, oaks3 more rows
Why are leaves broad?
Green leaves are thin and broad to increase the surface area for absorption of light and carbon dioxide.
What is membrane distillation?
Membrane distillation (MD) is an emerging technology for the desalination of brines. In some cases, liquid penetrates into the pores of the membrane, causing pore wetting. MD’s commercialization is hindered largely due to the occurrence of pore wetting phenomena since it results in the reduction of flux and/or permeate quality. Hence, it is of crucial importance for MD to prevent pore wetting from occurring. In this paper, the methods of detecting pore wetting and the membrane parameters related to this phenomenon are reviewed and possible sources of MD pore wetting occurrence are identified. Moreover, the methods to prepare membranes specifically designed for the mitigation of membrane wetting, such as the design of membrane materials, membrane surface modification, preparation of nanocomposite membranes by the addition of nanoparticles, dual-layered membranes, and membranes with a re-entrant structure are discussed. Finally, process-based approach for wetting mitigation, mainly by the pretreatment of the feed solution, is elucidated, and models for wetting phenomena are also outlined. Thus, attempts are made in this review to discuss all aspects of the pore wetting of MD membranes.
What is the role of biofilms in a biofilm?
Biofilms are structured microbial communities attached to surfaces, which play a significant role in the persistence of biofoulings in both medical and industrial settings. Bacteria in biofilms are mostly embedded in a complex matrix comprised of extracellular polymeric substances that provide mechanical stability and protection against environmental adversities. Once the biofilm is matured, it becomes extremely difficult to kill bacteria or mechanically remove biofilms from solid surfaces. Therefore, interrupting the bacterial surface sensing mechanism and subsequent initial binding process of bacteria to surfaces is essential to effectively prevent biofilm-associated problems. Noting that the process of bacterial adhesion is influenced by many factors, including material surface properties, this review summarizes recent works dedicated to understanding the influences of surface charge, surface wettability, roughness, topography, stiffness, and combination of properties on bacterial adhesion. This review also highlights other factors that are often neglected in bacterial adhesion studies such as bacterial motility and the effect of hydrodynamic flow. Lastly, the present review features recent innovations in nanotechnology-based antifouling systems to engineer new concepts of antibiofilm surfaces.
What are water striders?
Water striders have intrigued researchers for centuries from the viewpoints of biology to biomechanics. In this review, we introduce the basic theories and techniques of physics and force measurement for biomechanical research into water striders. Morphological and behavioral traits of water striders are summarized and discussed from biomechan ical perspectives, along with comparative study. This integrated review also highlights potential directions for studies on water-walking arthropods, which might inspire future biological and biomechanical research.
What is a dispensing nozzle?
A dispensing nozzle is an essential mechanical element in inkjet, dot, and bioprinting. To improve the printing resolution, the inner diameter of the nozzle outlet must be as small as possible. A droplet dispensed through a hydrophilic stainless steel outlet expands on the whole outlet surface and along the side surface of the nozzle. This issue can be solved by physical surface modifications. In the present paper, a femtosecond laser micro-/nano-texturing method was developed to transform the originally hydrophilic stainless steel surface of a nozzle to a hydrophobic or superhydrophobic one. First, an AISI304 plate was used to demonstrate experimentally that, on its surface, the tailored micro-/nano-patterns were reproduced as micro-/nano-textures, making the surface superhydrophobic. Second, the technique was applied to the physical surface modification of an AISI304 stainless steel nozzle outlet by optimizing the femtosecond laser machining conditions. A high-speed camera was used to take a snapshot of the dispensed droplet from the surface-modified outlet. Finally, a line-printing experiment was performed to characterize the dispensing behavior of the stainless steel nozzles with and without physical surface modification.
What is the contact angle of CF3?
[46] [47] [48] [49] [50] These surfaces are deemed "superhydrophobic" and display a contact angle in excess of 150°. This is only possible through the combination of hydrophobicity and roughness such that a liquid is suspended in a composite interface with the roughness; this leads to liquids easily beading up and rolling off the surface. ...
What is the use of sonochemistry for nanomaterials?
The use of sonochemistry for nanomaterials' synthesis has been recently employed for the associated shorter reaction times and efficient route for control over crystal growth and the management of the resulting material's photocatalytic properties. Moreover, the sol-gel method coupled to sonochemistry modifies the chemical environment, with reactive species such as •OH and H2O2, which yield a homogeneous synthesis. Therefore, in the following investigation, the sol-gel method was coupled to sonochemistry to synthesize a SiO2@TiO2 composite, for which the sonochemical amplitude of irradiation was varied to determine its effect on the morphology and mechanical and self-cleaning properties. SEM and AFM characterized the samples of [email protected] composite, and while the micrographs indicate that a high ultrasonic energy results in an amorphous SiO2@TiO2 composite with a low rugosity, which was affected in the determination of the contact angle on the surface. On the other hand, FTIR analysis suggests a significant change in both SiO2-SiO and SiO2-TiO2 chemical bonds with changes in vibrations and frequency, corroborating an important influence of the sonochemical energy contribution to the hydrolysis process. Raman spectroscopy confirms the presence of an amorphous phase of silicon dioxide; however, the vibrations of TiO2 were not visible. The evaluation of hydrophobic and self-cleaning properties shows a maximum of ultrasonic energy needed to improve the contact angle and rhodamine B (RhB) removal.
What are the problems caused by ice nucleation?
Ice nucleation and accretion leads to multiple problems such as freezing of the streets which can cause traffic collisions or people injuries, and collapse of high voltage power lines leading to black-out and icing of aircraft components , causing major aeronautic accidents. The most widespread strategies for the removal of accumulated ice layers result in most cases being expensive, time-consuming and hazardous for the environment. In this work we present the design of hydrophobic hybrid inorganic-organic coatings via Lotus leaf-like and slippery liquid infused porous surfaces (SLIPS) approaches with reduced, lasting wetting performance in cold environments. Static and dynamic wetting behavior was evaluated at room and sub-zero temperatures. The main target was the selection of the most suitable design approaches and formulations of coatings to be applied on metals or alloys when the contact time between the droplet and the material surface has to be minimized. In the temperature range from −10 to 0 °C, we report evidence of a stable hydrophobicity and a low water contact angle hysteresis (below 15°) of all the SLIPS developed. The surfaces’ ability to keep their wetting performance unchanged during the freeze/and frost/thaw durability cycles stood out as a key issue for further development at larger scale.
Biomimetics
1. Choose citation style Select style Vancouver APA Harvard IEEE MLA Chicago
1. Introduction
As early as the eleventh century, the Song dynasty of China, one scholar named Zhou Dunyi (1017–1073), had planted the lotus all over the poll in his home and wrote an article named Ode to A Lotus Flower.
3. Methods for the Preparation of the Superhydrophobic Surfaces
The Layer-by-Layer assembly technique, which was developed by Decher’s group, has been proved to be a simple and inexpensive way to build controllable chemical composition and micro- and nanometer scale ( Decher & Hong, 1991 ).
4. The Category of the Artificial Superhydrophobic Materials
Carbon nanotubes are new type of carbon structures which was discovered in 1991. Due to their excellent electrical and mechanical properties, the carbon nanotubes are widely used in both fundamental and applied research. Jiang and coworkers prepared an aligned carbon nanotubes films with micro- and nanometer structure.
5. The Superhydrophobic Surfaces Related Properties and Application
With more and more in-depth study on the preparation of the superhydrophobic surfaces, the materials researchers are not only satisfy with the preparation and the contact model of the superhydrophobic surface, but the application and the related properties of the superhydrophobic surfaces.
6. Outlook and Summary
In this chapter, we have presented the origin model of the superhydrophobicty in nature, the lotus leaf. In the following text, the mechanism of the surface resisting water, the recent studies on the biomimetic preparation and the properties of the superhydrophobic surface were elaborated.
Acknowledgments
This work was financially supported by the Natural Science Foundation of Shannxi Province, China (Grant No. 2009JQ2010), the Natural Science Research Project of Education Department of Shannxi Province, China (Grant No. 09JK580) and the Peiyu Fund of Xi’an University of Science and Technology (Grant No. 200818).
What is superhydrophobicity in plants?
The surface of a lotus leaf is an example of superhydrophobicity. On a superhydrophobic surface, the contact angle is greater than 150 o, meaning almost no wetting of the surface by the liquid takes place. This leads to the second property associated with lotus plants — the ability to stay spotlessly clean.
What happens when dew condenses on a lotus leaf?
In nature, when dew condenses on lotus leaves, the dew soon rolls off the leaf, just as water droplets falling onto the leaf do. However, when scientists began to study the superhydrophobic properties of the lotus leaf, they discovered water behaved differently in laboratories.
What is the lotus flower?
The lotus flower is a symbol of purity in many Asian cultures. The plant is "self-cleaning" due to its superhydrophobic leaves. copyright. ...
How tall are lotus leaf protrusions?
Each protrusion is itself covered in bumps of a hydrophobic, waxy material that are roughly 100 nm (1 x 10 -7 m) in height. When water droplets are applied to the lotus leaf, they sit lightly on the tips of the hydrophobic protrusions as if on a bed of nails (see Figure 2).
Where does water droplet sit?
In the Cassie-Baxter state, the water droplet sits on top of the rough surface with a layer of air underneath. When water is dropped or poured onto superhydrophobic surfaces, the water droplets sit lightly on the very tips of the surface protrusions, leaving a layer of air between the droplets and the leaf surface.
Is water vapor superhydrophobic?
Water poured or dropped on leaves in a controlled setting still demonstrated superhydrophobic properties. However, when water vapor was allowed to condense onto a lotus leaf in the lab, the water droplets were "sticky" and clung to the leaves. Figure 4. The Wenzel wetting state.
Do lotus plants stay spotless?
This leads to the second property associated with lotus plants — the ability to stay spotlessly clean. As rain falls on a superhydrophobic surface like the lotus leaf, the water droplets roll easily off the leaf surfaces (see Figure 3).
What is the water repellent of lotus leaf?
The lotus leaf possesses a peculiar water-repellent characteristic that enhances the mobility of oplets for self-cleaning purposes [1]. A similar effect, i.e. superhydrophobicity, enables a water strider to walk on wa- r [2].
What is superhydrophobicity used for?
Superhydrophobicity, often referred to as the lotus effect, could be utilized to design surfaces with minimal skin-friction drag for applications such as self-cleaning and energy conservation.
What happens when a superhydrophobic surface is fully submersed in water?
When a superhydrophobic surface is fully submersed in water, it entraps air in its pores resulting in the formation air pockets between the solid surface and water. The entrapped air is separated from water with a thin interface anchored the solid walls and stretched due to surface tension forces.
Is a lotus leaf a symbol of purity?
Accordingly, the lotus leaf is a symbol purity in some Asian religions [1]. To demonstrate the importance of nanoscale wax crystals on the lotus effect, Cheng et al. [12] altered the surface struc- re of a lotus leaf without affecting the chemical composition.
What is the Lotus effect?
Before we dive into the "Lotus effect" (superhydrophobicity), it is important to have an understanding of a concept called surface energy. Imagine the animation below displays an infinite array of atoms bonded together - an infinitely large piece of material. If we were to cut a shape out of this material we'd be creating a surface, and in creating a surface we would have to break bonds between atoms (represented below as blue circles). Atoms form bonds because it allows them to exist at a lower-energy state, so it takes energy in order to break these bonds and create a surface. This energy required to break the bonds is known as surface energy.
What is the structure of a lotus leaf?
In summary, the structure of a lotus leaf has a clever design that discourages surface wetting both through a waxy nonpolar coating and a rough structure which both make surface interactions less favorable, allowing water to bead up into spheres and easily roll off the leaf.
What is hydrophobic material?
Hydrophobic materials can be useful in a myriad of applications, basically anywhere where you don't want your things to get wet. To figure out how to engineer materials with better hydrophobic properties, scientists have turned to nature (specifically, the lotus leaf) to study its intelligent design. Lotus leaves (pictured below) ...
Is Lotus a superhydrophobic plant?
Lotus leaves (pictured below) are well known for being superhydrophobic, so they serve as an excellent case study. Note: the concept of studying nature's design and using solutions developed by nature over thousands of years is known as biomimicry.
What is superhydrophobic coating?
Superhydrophobic coating. A superhydrophobic coating is a thin surface layer that repels water. It is made from superhydrophobic ( ultrahydrophobicity) materials. Droplets hitting this kind of coating can fully rebound. Generally speaking, superhydrophobic coatings are made from composite materials where one component provides the roughness and ...
How can a surface be hydrophobic?
Surfaces can be made hydrophobic without the use of coating through the altering of their surface microscopic contours , as well. The basis of hydrophobicity is the creation of recessed areas on a surface whose wetting expends more energy than bridging the recesses expends.
Is stainless steel hydrophobic?
Newer engineered surface textures on stainless steel are extremely durable and permanently hydrophobic. Optically these surfaces appear as a uniform matte surface but microscopically they consist of rounded depressions one to two microns deep over 25% to 50% of the surface.
