Superhydrophobic, electrically conductive and multifunctional polymer foam composite for chemical vapor detection and crude oil cleanup.

The leakage of chemicals (either vapors or liquids) severely threatens the environment and even people's health. It remains a great challenge to develop multifunctional and durable materials that can not only detect the chemical vapors but also clean up the liquid chemicals especially high viscous crude oil. Here, a superhydrophobic and conductive foam composite (SCFC) is prepared by decorating carbon black nanoparticles (CBNPs) onto the skeleton of the pre-swollen polymer foam under the assistance of ultrasonication. The CBNPs are firmly embedded onto the skeleton surface, exhibiting a strong interfacial adhesion and hence excellent surface stability and durability. The SCFC possesses stable vapor sensing behavior and can detect various chemical vapors with a low detection limit and good cycling performance. When used for oil/water separation, the SCFC has large oil adsorption capacity for different oils with excellent reusability. Also, the outstanding photo-thermal conversion performance of the SCFC can be used to significantly reduce the oil viscosity and hence realize efficient cleanup of the crude oil. The multifunctional SCFC has promising applications in the field of environment protection, flexible electronics, etc.

Interface-engineered reduced graphene oxide assembly on nanofiber surface for high performance strain and temperature sensing.

Conductive polymer nanofiber composites (CPNCs) based wearable sensing electronics have aroused great attention of scientists in recent years. However, it is still difficult to obtain CPNCs with good water proof, excellent durability, and multiple sensing performance. Herein, we develop a multifunctional CPNC with a wrinkled reduced graphene oxide (RGO) shell and polymer nanofiber core, which is prepared by ultrasonication induced decoration of RGO onto the pre-stretched polyurethane (PU) nanofibers, followed by the release of the strain. The RGO assembly with a wrinkled structure not only greatly increases the surface roughness and thus the hydrophobicity but also enhances the strain sensing sensitivity (with a gauge factor of 154.8 in the strain range of 85%-100%) of the nanofibrous membrane. The obtained CPNC strain sensor also shows excellent sensing durability (over 1000 cycles) and can be used for body motion monitoring. The CPNC shows a negative temperature coefficient effect, which holds promising applications in high performance temperature sensors.

Superhydrophobic, mechanically durable coatings for controllable light and magnetism driven actuators.

Although some groundbreaking work has proved the feasibility of non-contact Marangoni propulsion generated by combination of the superhydrophobicity and photothermal effect, there are still challenges including the strong interfacial adhesion, multifunctional structural design and superior durability. In this paper, a simple two-step spraying method is used to prepare superhydrophobic and multi-functional fluorinated acidified carbon nanotubes (F-ACNTs)/Fe3O4 nanoparticles/polydimethylsiloxane (PDMS) coatings. The introduction of Fe3O4 nanoparticles and F-ACNTs not merely improve the surface roughness but also endow the coating with the outstanding magnetic property and photothermal conversion performance. The PDMS can reduce the surface energy and also improve the interfacial adhesion between the nanofillers and the substrate (the filter paper). The superhydrophobicity can be maintained when the material experiences abrasion, near-infrared (NIR) light irradiation and acid treatment, exhibiting outstanding durability. The highly stable superhydrophobic coating introduces a thin layer of air to decrease the drag force between the filter paper and the water surface, and can be used for controlled self-propelled light-driven motion and magnetic-driven motion. The movement can be manipulated by adjusting the direction of the incident NIR light and magnetic field. In particular, the superhydrophobic and superoleophilic coating based actuators can be easily driven to the oil-contaminated area on the water surface by using a magnet for high efficiency oil removal. This work provides a simple and universal strategy for developing intelligent and multi-responsive actuators possessing promising applications in various fields such as environmental protection, micro-robots and biomedicine.

Flexible, superhydrophobic and multifunctional carbon nanofiber hybrid membranes for high performance light driven actuators.

Recently, a series of super-hydrophobic materials have been prepared and efforts have been made to further expand their applications, especially in electronics and smart actuators. However, it remains challenging to develop light weight, flexible and super-hydrophobic materials integrating multifunctionalities such as superior photothermal conversion, corrosion resistance, and controllable actuation. Herein, a superhydrophobic and multi-responsive carbon nanofiber (CNF) hybrid membrane with an outstanding photo-thermal effect is fabricated by electrospinning the mixture of polyacrylonitrile and nickel acetylacetonate, followed by two step heat treatment and subsequent fluorination. The superhydrophobic CNF hybrid membrane with outstanding anti-corrosion and self-cleaning performance can float on the water surface spontaneously, thus effectively reducing the motion resistance. The light driven actuation with controllable movement can be achieved by adjusting the laser irradiated location, in which the localized absorption of light is transformed into thermal energy, and hence an imbalanced surface tension is created. The multifunctional hybrid membrane also opens up an arena of applications such as freestanding flexible electronics, drug delivery, and environmental protection.

Polyvinylpyrrolidone Assisted Preparation of Highly Conductive, Antioxidation, and Durable Nanofiber Composite with an Extremely High Electromagnetic Interference Shielding Effectiveness.

With booming development of electronics, electromagnetic interference (EMI) shielding materials based on conductive polymer composites (CPCs) have received increasing attention. However, it remains challenging to develop flexible and lightweight CPCs with excellent stretchability, breathability, durability, and high EMI shielding effectiveness (EMI SE). Here, we propose a facile polyvinylpyrrolidone (PVP) assisted preparation of highly electrically conductive and durable nanofiber composites for high performance EMI shielding. The PVP layer could not only greatly enhance the interfacial interaction between the Ag nanoparticles (AgNPs) and hence the mechanical properties (both tensile strength, Young's modulus and elongation at break) of the polymer nanofiber membrane but also forms a protection layer preventing the AgNPs from oxidizing. The electrical conductivity of the nanofiber composite can reach up to 245.7 ± 30.6 S/cm, which is, to a large degree, maintained after cyclic stretching, abrasion, and ultrasonic washing. In addition, the nanofiber composite exhibits excellent breathability, antibacterial, and Joule heating performance. When used as the EMI shielding material, the nanofiber composite shows an extremely high SE and SSE of ∼96.9 dB and 169.7 dB cm3/g, respectively, and EMI shielding performance possesses outstanding stability and durability. This multifunctional nanofibrous composite membrane exhibits promising applications in wearable electronics.

Carbon nanofiber based superhydrophobic foam composite for high performance oil/water separation.

Oil spill has now been a serious environmental issue, threatening the aquatic ecosystems and even human living environment. It is still challenging to develop absorbents for efficient oil/water emulsion separation and clean-up of viscous crude oil. Here, we propose a facile method to fabricate flexible and superhydrophobic foam composites for high efficiency oil/water separation under different complex environment. Carbon nanofibers (CNFs) with a hollow structure are decorated uniformly onto the skeleton of the polydimethylsiloxane (PDMS) foam with a strong interfacial adhesion. CNFs could not only enhance the surface roughness and thus the hydrophobicity but also be served as numerous capillary tubes, improving the oil adsorption and oil/water separation performance. More importantly, the CNFs network with a strong light absorption endows the foam with superior photo-thermal conversion capability. The obtained foam composite possesses excellent corrosion resistance and can adsorb various kinds of oil with different densities. The foam composite is able to separate the oil from the emulsion with a relatively high separation efficiency. The material surface temperature is able to quickly increase under the light irradiation, which can significantly reduce the oil viscosity and hence achieve the rapid clean-up of the crude oil floating on water surface.

Self-Derived Superhydrophobic and Multifunctional Polymer Sponge Composite with Excellent Joule Heating and Photothermal Performance for Strain/Pressure Sensors.

Flexible strain or pressure sensors have potential applications in electronic skin, healthcare, etc. It remains a challenge to explore multifunctional strain or pressure sensors that possess excellent water repellent and heating performance and hence can be used in harsh environments such as high moisture and low-temperature conditions. Here, a self-derived superhydrophobic and multifunctional polymer composite foam is prepared by adsorption of the Ag precursor in tetrahydrofuran (THF) onto the rubber sponge followed by reduction of Ag+ to Ag nanoparticles (AgNPs). During the Ag+ reduction in hydrazine solution, the swollen rubber sponge by THF is partially precipitated based on the nonsolvent-induced phase separation (NIPS). The NIPS creates a porous structure on the sponge surface and thus a high surface roughness, contributing to the material superhydrophobicity. The precipitated polymer wrapping the AgNPs could enhance the interaction between the individual AgNPs. The obtained conductive sponge composite possesses excellent Joule heating and photothermal performance and can be used as both a strain and pressure sensor. The conductive sponge composite sensor possesses good reliability and durability and can be applied to real-time monitoring of human body movements.

Durable and Multifunctional Superhydrophobic Coatings with Excellent Joule Heating and Electromagnetic Interference Shielding Performance for Flexible Sensing Electronics.

Superhydrophobic coatings have wide applications in many fields. However, superhydrophobic and smart coatings with multifunctionality and their applications in flexible sensing electronics are seldom reported. In this work, durable, superhydrophobic, and anticorrosive coatings with excellent Joule heating and electromagnetic interference (EMI) shielding performance are prepared on the basis of Ag precursor reduction and synchronous nonsolvent induced phase separation. Silver nanoparticles (AgNPs) coated with the copolymer (polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene: SEBS) are uniformly distributed on the target substrate, forming mechanically durable conductive network. SEBS could not only endow the surface coating with superhydrophobicity but also improve the interaction among individual Ag nanoparticles and the interfacial adhesion between AgNPs and the substrate. The multifunctional coating possesses excellent anticorrosive, self-cleaning, and deicing properties. The high conductivity endows the coatings with excellent Joule heating and EMI shielding performance. The multifunctional coating can be applied to a variety of different substrates with outstanding surface stability and reliability. The conductivity for the smart coating can reach as high as 107 S/cm with the EMI shielding effectiveness up to 37.8 dB. At a low applied voltage of 1 V, the conductive fabric can be heated up to over 80 °C in 60 s and displays good recyclability during dozens of heating and cooling cycles. The Joule heating-induced temperature increase could be used for efficient surface deicing. When used for the flexible and wearable strain sensors, the multifunctional coating has a very low strain detection limit of 0.5% and large sensitivity (with the gauge factor as high as 1075) and excellent repeatability. In addition, it can be used for precisely monitoring different body motions, including both large and subtle joint movement.

Fluorine-free Superhydrophobic and Conductive Rubber Composite with Outstanding Deicing Performance for Highly Sensitive and Stretchable Strain Sensors.

Conductive polymer composite (CPC) based strain sensor due to its lightweight, tunable electrical conductivity, and easy processing has promising application in wearable electronics. However, it is still challenging to develop the CPC strain sensors with excellent stretchability, sensitivity, durability, anticorrosion, and deicing performance. Herein, a facile method is proposed to prepare fluorine-free superhydrophobic and highly conductive rubber composite. Ag nanoparticles (AgNPs) are first decorated on the RB (rubber band) surface, forming a conductive shell. Then, the RB/AgNPs experiences PDMS (polydimethylsiloxane) modification, which could not only endow the composite with superhydrophobicity and hence excellent corrosion resistance but also improve the interfacial adhesion between the AgNPs. The RB composite possesses a good self-cleaning performance and remains superhydrophobic even after experiencing cyclic abrasion or stretching-releasing test. Also, the high conductivity and superhydrophobicity endow the RB composite with excellent Joule heating performance and water repellence, broadening its application in deicing and water removal. Moreover, the obtained RB composite exhibits both large stretchability with a break elongation larger than 900% and high sensitivity with a response intensity as high as 3.6 × 108 at a strain of 60%. In addition, the RB composite strain sensor can be used to detect full-range human motions including large and subtle body movement. The flexible, durable, and anticorrosive RB composite has potential applications in flexible electronic, health monitoring, physical therapy, and so on.

Mechanically Durable, Highly Conductive, and Anticorrosive Composite Fabrics with Excellent Self-Cleaning Performance for High-Efficiency Electromagnetic Interference Shielding.

Metal-based materials have been widely used for the electromagnetic interference (EMI) shielding due to their excellent intrinsic conductivity. However, their high density, poor corrosion resistance, and poor flexibility limit their further application in aerospace and flexible electronics. Here, we reported a facile means to prepare lightweight, mechanically durable, superhydrophobic and conductive polymer fabric composites (CPFCs) with excellent electromagnetic shielding performance. The CPFC could be fabricated by three steps: (1) the polypropylene (PP) fabric was coated by a polydopamine (PDA) layer; (2) PP/PDA adsorbed the Ag precursor that was then chemically reduced to Ag nanoparticles (AgNPs); (3) PP/PDA/AgNPs fabrics were modified by one layer of polydimethylsiloxane (PDMS). The contact angle (CA) of the CPFCs could reach ∼152.3° while the sliding angle (SA) was as low as ∼1.5°, endowing the materials with excellent self-cleaning performance. Thanks to the extremely high conductivity of 81.2 S/cm and the unique porous structure of the fabric, the CPFC possessed outstanding EMI shielding performance with the maximum shielding effectiveness (SE) of 71.2 dB and the specific shielding effectiveness (SSE) of 270.7 dB cm3 g-1 in the X band. The interfacial adhesion is remarkably improved owing to the PDMS layer, and the superhydrophobicity, conductivity and EMI SE of CPFCs are almost maintained after cyclic abrasion and winding test. Also, the CPFCs can be used in a harsh environment, due to their excellent water proof property.