Durability of multi-walled carbon nanotube reinforced concrete

The research and development of wearable sensors have gained a growing interest due to the advantage of being flexible, thin, and light, which makes them highly desirable for robotic and healthcare applications. One of the essential devices in wearable technology is flexible temperature sensors for body temperature detection. Recent advances in flexible temperature sensors based on nanomaterials and conductive polymers are evaluated in this review. The temperature-responsive mechanisms, temperature-sensitive materials, and production methods of temperature sensors and recent outcomes of related papers are explained and classified in a detailed perspective. The flexible temperature sensors based on nanomaterial-filled polymer composites, printed/coated conductors, and textiles are explained in terms of structures and performances by giving examples from recent literature studies. The reliability and challenges of flexible temperature sensors are outlined from the point of view of structural design and implementation.

Flexible temperature sensors: A review

Effect of carbon nanotubes on compressive, flexural and tensile strengths of Portland cement-based materials: A systematic literature review

Carbon nanotubes (CNTs) are considered as one of the ideal materials due to their high surface area, high aspect ratio, and impressive material properties, such as mechanical strength, and thermal and electrical conductivity, for the manufacture of next generation composite materials. In spite of the mentioned attractive features, they tend to agglomerate due to their inherent chemical structure which limits their application. Surface modification is required to overcome the agglomeration and increase their dispersability leading to enhanced interactions of the functionalized CNTs with matrix materials/polymer matrices. Recent developments concerning reliable methods for the functionalization of carbon nanotubes offer an additional thrust towards extending their application areas. By chemical functionalization, organic functional groups are generated/attached to the surfaces as well as the tip of CNTs which opens up the possibilities for tailoring the properties of nanotubes and extending their application areas. Different research efforts have been devoted towards both covalent and non-covalent functionalization for different applications. Functionalized CNTs have been used successfully for the development of high quality nanocomposites, finding wide application as chemical and biological sensors, in optoelectronics and catalysis. Non covalently functionalized carbon nanotubes have been used as a substrate for the immobilization of a large variety of biomolecules to impart specific recognition properties for the development of miniaturized biosensors as well as designing of novel bioactive nanomaterials. Functionalized CNTs have also been demonstrated as one of the promising nanomaterials for the decontamination of water due to their high adsorption capacity and specificity for various contaminants. Specifically modified CNTs have been utilized for bone tissue engineering and as a novel and versatile drug delivery vehicle. This review article discusses in short the synthesis, properties and applications of CNTs. This includes the need for functionalization of CNTs, methods and types of functionalization, and properties of functionalized CNTs and their applications especially with respect to material and biomedical sciences, water purification, and drug delivery systems.

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Functionalized carbon nanotubes: synthesis, properties and applications in water purification, drug delivery, and material and biomedical sciences

Hybrid graphene oxide/carbon nanotubes reinforced cement paste: An investigation on hybrid ratio

Dispersion of carbon nanotubes (CNTs) is a challenge for their application in the resulting matrixes. The present study conducted a comparison investigation of the effect of four surfactants: Alkylphenol polyoxyethylene ether (APEO), Silane modified polycarboxylate (Silane-PCE), I-Cationic polycarboxylate (I-C-PCE), and II-Cationic polycarboxylate (II-C-PCE) on the dispersion of hydroxyl functionalized multi-walled carbon nanotubes (MWCNTs–OH). Among the four surfactants, APEO and II-C-PCE provide the best and the worst dispersion effect of CNTs in water, respectively. Dispersion effect of MWCNTs–OH has been characterized by optical microscope (OM), field emission-scanning electron microscope (FE-SEM), and Ultraviolet–visible spectroscopy (UV–Vis).The OM images are well consistent with the UV–Vis results. Based on the chemical molecular structures of the four surfactants, the mechanism of MWCNTs–OH dispersion in water was investigated. For each kind of surfactant, an optimum surfactant/MWCNTs–OH ratio has been determined. This ratio showed a significant influence on the dispersion of MWCNTs–OH. Surfactant concentration higher or lower than this value can weaken the dispersion quality of MWCNTs–OH.

Effects of Various Surfactants on the Dispersion of MWCNTs-OH in Aqueous Solution.

Carbon nanotubes (CNTs) have excellent mechanical properties and can be used to reinforce cement-based materials. On the other hand, the reaction product of carbonation with hydroxides in hydrated cement paste can reduce the porosity of cement-based materials. In this study, a novel method to improve the strength of cement paste was developed through a synergy of carbon nanotubes decorated with carboxyl group and carbonation reactions. The experimental results showed that the carboxyl group (–COOH) of decorated carbon nanotubes and the surfactant can control the morphology of the calcium carbonate crystal of carbonation products in hydrated cement paste. The spindle-like calcium carbonate crystals showed great morphological differences from those observed in the conventional carbonation of cement paste. The spindle-like calcium carbonate crystals can serve as fiber-like reinforcements to reinforce the cement paste. By the synergy of the carbon nanotubes and carbonation reactions, the compressive and flexural strengths of cement paste were significantly improved and increased by 14% and 55%, respectively, when compared to those of plain cement paste.

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Study on Utilization of Carboxyl Group Decorated Carbon Nanotubes and Carbonation Reaction for Improving Strengths and Microstructures of Cement Paste.

Bubbles have been extensively explored as energy carriers ranging from boiling heat transfer and targeted cancer diagnosis. Yet, despite notable progress, the kinetic energy inherent in small bubbles remains difficult to harvest. Here, we develop a transistor-inspired bubble energy generator for directly and efficiently harvesting energy from small bubbles. The key points lie in designing dielectric surface with high-density electric charges and tailored surface wettability as well as transistor-inspired electrode configuration. The synergy between these features facilitates fast bubble spreading and subsequent departure, transforms the initial liquid/solid interface into gas/solid interface under the gating of bubble, and yields an output at least one order of magnitude higher than existing studies. We also show that the output can be further enhanced through rapid bubble collapse at the air/liquid interface and multiple bubbles synchronization. We envision that our design will pave the way for small bubble-based energy harvesting in liquid media.

Bubble energy generator

Manipulating liquid is of great significance in fields from life sciences to industrial applications. Owing to its advantages in manipulating liquids with high precision and flexibility, electrowetting on dielectric (EWOD) has been widely used in various applications. Despite this, its efficient operation generally needs electrode arrays and sophisticated circuit control. Here, we develop a largely unexplored triboelectric wetting (TEW) phenomenon that can directly exploit the triboelectric charges to achieve the programmed and precise water droplet control. This key feature lies in the rational design of a chemical molecular layer that can generate and store triboelectric charges through agile triboelectrification. The TEW eliminates the requirement of the electric circuit design and additional source input and allows for manipulating liquids of various compositions, volumes, and arrays on various substrates in a controllable manner. This previously unexplored wetting mechanism and control strategy will find diverse applications ranging from controllable chemical reactions to surface defogging.

Triboelectric wetting for continuous droplet transport

Harnessing ambient renewable mechanical energies for achieving carbon‐neutrality demands the rational design of materials and architectures which are favorable for both energy collection and conversion simultaneously. However, the direct coupling of energy collection and conversion modules leads to many unwanted problems such as material wearing, the spatial constraint for large‐scale integration, and low energy conversion efficiency. Herein, a remote‐controlled energy harvesting strategy that cleverly harnesses the unique advantage of diffusive, long‐range airflow within a confined capillary channel is developed. The reported device separates the energy collection unit, made of an elastic cavity that directly transforms external mechanical motion to pneumatic motion, from the conversion units, made of encapsulated droplet chains that serve to translate their recurring motion within the capillary channel into electrical output. In contrast to single‐drain electrode design for electricity generation from fresh droplets in open spaces, two drain electrodes are designed to collect and release electrostatically induced charges from recurring droplets in the confined channel, respectively, thereby eliminating unwanted charge accumulation on recurring droplets and leading to efficient output performance. The integration of multiple electricity generation units with such a two‐drain electrode architecture with a single energy collector improves the design resilience and relaxes the spatial limitation.

Xiantong Yan

Papers

Effects of Various Surfactants on the Dispersion of MWCNTs-OH in Aqueous Solution.

Study on Utilization of Carboxyl Group Decorated Carbon Nanotubes and Carbonation Reaction for Improving Strengths and Microstructures of Cement Paste.

Bubble energy generator

Triboelectric wetting for continuous droplet transport

Remote‐Controlled Droplet Chains‐Based Electricity Generators