8 research outputs found
Magnetically Induced Reversible Transition between Cassie and Wenzel States of Superparamagnetic Microdroplets on Highly Hydrophobic Silicon Surface
In this work, we report a magnetic technique for reversible
wetting–dewetting
transitions of microdroplets on highly hydrophobic surfaces. A superparamagnetic
microdroplet can be reversibly switched between the Cassie state and
the Wenzel state on a highly hydrophobic microstructured silicon substrate
by the application of the magnetic field. The transition can be controlled
by both the intensity of the magnetic field and the concentration
of the superparamagnetic Fe<sub>3</sub>O<sub>4</sub> nanoparticles
in the microdroplet. The magnetic force needed during the transition
from the Cassie state to the Wenzel state was found to be apparently
smaller than that needed in the reverse process. Such asymmetry is
ascribed to the higher energy of the Cassie state compared with the
Wenzel state, the change of the gravitational potential energy, and
the adhesion hysteresis. This report provides a novel method of dynamically
controlling liquid/solid interactions, which can not only help us
to understand further the transition between the Cassie state and
the Wenzel state but also potentially be used in some important applications,
such as lab-on-a-chip devices and chemical microreactors
Under-Oil Switchable Superhydrophobicity to Superhydrophilicity Transition on TiO<sub>2</sub> Nanotube Arrays
Recently,
smart interfacial materials that can reversibly transit
between the superhydrophobicity and superhydrophilicity have aroused
much attention. However, all present performances happen in air, and
to realize such a smart transition in complex environments, such as
oil, is still a challenge. Herein, TiO<sub>2</sub> nanotube arrays
with switchable transition between the superhydrophobicity and superhydrophilicity
in oil are reported. The switching can be observed by alternation
of UV irradiation and heating process, and the smart controllability
can be ascribed to the cooperative effect between the surface nanostructures
and the chemical composition variation. By using the controllable
wetting performances, some applications such as under-oil droplet-based
microreaction and water-removal from oil were demonstrated on our
surface. This paper reports a surface with smart water wettability
in oil, which could start some fresh ideas for wetting control on
interfacial materials
Under-Oil Switchable Superhydrophobicity to Superhydrophilicity Transition on TiO<sub>2</sub> Nanotube Arrays
Recently,
smart interfacial materials that can reversibly transit
between the superhydrophobicity and superhydrophilicity have aroused
much attention. However, all present performances happen in air, and
to realize such a smart transition in complex environments, such as
oil, is still a challenge. Herein, TiO<sub>2</sub> nanotube arrays
with switchable transition between the superhydrophobicity and superhydrophilicity
in oil are reported. The switching can be observed by alternation
of UV irradiation and heating process, and the smart controllability
can be ascribed to the cooperative effect between the surface nanostructures
and the chemical composition variation. By using the controllable
wetting performances, some applications such as under-oil droplet-based
microreaction and water-removal from oil were demonstrated on our
surface. This paper reports a surface with smart water wettability
in oil, which could start some fresh ideas for wetting control on
interfacial materials
Regulating Underwater Superoleophobicity to Superoleophilicity on Hierarchical Structured Copper Substrates through Assembling <i>n</i>‑Alkanoic Acids
In
this paper, we report a simple method based on assembling <i>n</i>-alkanoic acids on hierarchical structured copper toward
preparing surfaces with tunable oil wetting performance in water.
Surface wettability from superoleophobicity to superoleophilicity
in water can be regulated through tuning the chain length of <i>n</i>-alkanoic acids. Importantly, even in strongly acid and
basic water, such phenomena can still be observed. The cooperation
between the hierarchical structures and the surface chemical composition
variation is responsible for the controllability. Meanwhile, the tunable
ability is universal and the controllability is suitable for various
oils including silicon oil, <i>n</i>-hexane, and chloroform.
Moreover, the method was also used on copper mesh substrates, and
we reported the related application of selective oil/water separation.
This paper provides a flexible strategy toward preparing surfaces
with tunable oil wetting performances, which can also be suitable
for other materials, and offers some fresh ideas in manipulating underwater
oil wetting performances on surfaces
Underwater Superoleophilic to Superoleophobic Wetting Control on the Nanostructured Copper Substrates
Surfaces
with controlled underwater oil wettability would offer great promise
in the design and fabrication of novel materials for advanced applications.
Herein, we propose a new approach based on self-assembly of mixed
thiols (containing both HSÂ(CH<sub>2</sub>)<sub>9</sub>CH<sub>3</sub> and HSÂ(CH<sub>2</sub>)<sub>11</sub>OH) on nanostructured copper
substrates for the fabrication of surfaces with controlled underwater
oil wettability. By simply changing the concentration of HSÂ(CH<sub>2</sub>)<sub>11</sub>OH in the solution, surfaces with controlled
oil wettability from the underwater superoleophilicity to superoleophobicity
can be achieved. The tunable effect can be due to the synergistic
effect of the surface chemistry variation and the nanostructures on
the surfaces. Noticeably, the amplified effect of the nanostructures
can provide better control of the underwater oil wettability between
the two extremes: superoleophilicity and superoleophobicity. Moreover,
we also extended the strategy to the copper mesh substrates and realized
the selective oil/water separation on the as-prepared copper mesh
films. This report offers a flexible approach of fabricating surfaces
with controlled oil wettability, which can be further applied to other
ordinary materials, and open up new perspectives in manipulation of
the surface oil wettability in water
pH-Induced Reversible Wetting Transition between the Underwater Superoleophilicity and Superoleophobicity
Surfaces with controlled oil wettability
in water have great potential for numerous underwater applications.
In this work, we report a smart surface with pH-responsive oil wettability.
The surface shows superoleophilicity in acidic water and superoleophobicity
in basic water. Reversible transition between the two states can be
achieved through alteration of the water pH. Such smart ability of
the surface is due to the cooperation between the surface chemistry
variation and hierarchical structures on the surface. Furthermore,
we also extended this strategy to the copper mesh substrate and realized
the selective oil/water separation on the as-prepared film. This paper
reports a new surface with excellently controllable underwater oil
wettability, and we believe such a surface has a lot of applications,
for instance, microfluidic devices, bioadhesion, and antifouling materials
pH-Controllable On-Demand Oil/Water Separation on the Switchable Superhydrophobic/Superhydrophilic and Underwater Low-Adhesive Superoleophobic Copper Mesh Film
Recently, materials
with controlled oil/water separation ability became a new research
focus. Herein, we report a novel copper mesh film, which is superhydrophobic
and superhydrophilic for nonalkaline water and alkaline water, respectively.
Meanwhile, the film shows superoleophobicity in alkaline water. Using
the film as a separating membrane, the oil/water separating process
can be triggered on-demand by changing the water pH, which shows a
good controllability. Moreover, it is found that the nanostructure
and the appropriate pore size of the substrate are important for realization
of a good separation effect. This paper offers a new insight into
the application of surfaces with switchable wettability, and the film
reported here has such a special ability that allows it to be used
in other applications, such as sewage purification, filtration, and
microfluidic device
Regulating Underwater Oil Adhesion on Superoleophobic Copper Films through Assembling <i>n</i>‑Alkanoic Acids
Controlling
liquid adhesion on special wetting surface is significant
in many practical applications. In this paper, an easy self-assembled
monolayer technique was advanced to modify nanostructured copper substrates,
and tunable adhesive underwater superoleophobic surfaces were prepared.
The surface adhesion can be regulated by simply varying the chain
length of the <i>n</i>-alkanoic acids, and the tunable adhesive
properties can be ascribed to the combined action of surfaces nanostructures
and related variation in surface chemistry. Meanwhile, the tunable
ability is universal, and the oil-adhesion controllability is suitable
to various oils including silicon oil, <i>n</i>-hexane,
and chloroform. Finally, on the basis of the special tunable adhesive
properties, some applications of our surfaces including droplet storage,
transfer, mixing, and so on are also discussed. The paper offers a
novel and simple method to prepare underwater superoleophobic surfaces
with regulated adhesion, which can potentially be applied in numerous
fields, for instance, biodetection, microreactors, and microfluidic
devices