Conductive Aerogels Research Articles

Conductive, self-cleaning, and short-circuit proof multi-functional graphene aerogel composite fibers

Conductive, self-cleaning, and short-circuit proof multi-functional graphene aerogel composite fibers

Covalent Cross‐Links Enable the Formation of Ambient‐Dried Biomass Aerogels through the Activation of a Triazine Derivative for Energy Storage and Generation

AbstractAerogels hold promises as lightweight replacements in various applications but are plagued by their fabrication equipment, such as supercritical dryers or lyophilizers that need to work under extreme conditions. This study presents a covalent chemistry approach to strengthen cellulose nanofibers (CNF) with carboxymethylated chitosan (CMCs) to produce aerogels by ambient drying. The cross‐linking and gelation of the CNF and CMCs solutions are triggered by a triazine derivative, 4‐(4,6‐Dimethoxy[1.3.5]triazin‐2‐yl)‐4‐methylmorpholinium chloride hydrate, to form an amide bond. This approach leads to robust hydrogels that can resist capillary force during the ambient volatilization process and are turned into aerogels by freezing, solvent thawing and exchange, and ambient drying. The lightweight aerogels exhibit desirable qualities, including superior mechanical performance, a low density of 12.0 mg cm−3, and low shrinkage of 10.1%. The presented CMCs/CNF aerogels can also serve as a helpful carrier for conductive polymer, poly (3,4‐ethylene dioxythiophene):tosylate, through in situ polymerization to demonstrate their applications. These conductive aerogels are used for high‐performance supercapacitors and moisture‐enabled electrical generators. This study provides inspiration and a reliable approach for the elaborately structural design of aerogels at ambient conditions and endows application prospects in energy storage and generation opportunities.

Oxidative Self-Assembly of Au/Ag/Pt Alloy Nanoparticles into High-Surface Area, Mesoporous, and Conductive Aerogels for Methanol Electro-oxidation

Oxidative Self-Assembly of Au/Ag/Pt Alloy Nanoparticles into High-Surface Area, Mesoporous, and Conductive Aerogels for Methanol Electro-oxidation

Protein-Based Flexible Conductive Aerogels for Piezoresistive Pressure Sensors.

Gelatin is an excellent gelling agent and is widely employed for hydrogel formation. Because of the poor mechanical properties of gelatin when dry, gelatin-aerogels are comparatively rare. Herein we demonstrate that protein nanofibrils can be employed to improve the mechanical properties of gelatin aerogels, and the materials can moreover be functionalized with a an electrically conductive polyelectrolyte resulting in formation of an elastic electrically conductive aerogel that can be employed as a piezoresistive pressure sensor. The aerogel sensor shows a good linear relationship in a wide pressure range (1.8–300 kPa) with a sensitivity of 1.8 kPa–1. This work presents a convenient way to produce electrically conductive elastic aerogels from low-cost protein precursors.

3D MXene/PEDOT:PSS Composite Aerogel with a Controllable Patterning Property for Highly Sensitive Wearable Physical Monitoring and Robotic Tactile Sensing.

MXene based composite conductive aerogels have been extensively investigated as sensitive materials for wearable pressure sensors owing to their effective 3D network microstructures and the excellent conductivity of MXene. In this work, we fabricated a 3D porous Ti3C2Tx MXene/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) composite aerogel (MPCA) with a controllable patterning property utilizing the Cu-assisted electrogelation method. The prepared composite aerogel can be assembled into pressure sensors for wearable physical monitoring and high-resolution sensor microarrays for robotic tactile sensing. The multi-interactions between MXene and PEDOT:PSS enable the MPCA to have a stable 3D conductive network, which consequently enhances both the mechanical flexibility and the piezoresistive property of the MPCA. Thus, the fabricated pressure sensor demonstrating high sensitivity (26.65 kPa-1 within 0-2 kPa), fast response ability (106 ms), and excellent stability can be further applied for wearable physical monitoring. Moreover, due to the controllable patterning property of the electrogelation preparation method, a high-resolution pressure sensor microarray was successfully prepared as an artificial tactile interface, which can be attached to a robotic fingertip to directly recognize the tactile stimuli from human fingers and identify braille letters like human fingers. The proposed MPCA, endowed with a remarkable comprehensive property, particularly the highly sensitive sensing performance and controllable patterning property, demonstrates an enormous advantage and a great potentiality toward wearable electronics.

Multifunctional Superelastic, Superhydrophilic, and Ultralight Nanocellulose‐Based Composite Carbon Aerogels for Compressive Supercapacitor and Strain Sensor

AbstractDeveloping superelastic and superhydrophilic carbon aerogels with intriguing mechanical properties is urgently desired for achieving promising performances in highly compressive supercapacitors and strain sensors. Herein, based on synergistic hydrogen bonding, electrostatic interaction, and π–π interaction within regularly arranged layered porous structures, conductive carbon aerogels with cellulose nanofibrils (CNF), carbon nanotubes (CNT) and reduced graphene oxide (RGO) are developed via bidirectional freezing and subsequent annealing. Benefiting from the porous architecture and high surface roughness, CNF/CNT/RGO carbon aerogels exhibit ultralow density (2.64 mg cm–3) and superhydrophilicity (water contact angle ≈0° at 106 ms). The honeycomb‐like ordered porous structure can efficiently transfer stress in the entire microstructure, thereby endowing carbon aerogels with high compressibility and extraordinary fatigue resistance (10,000 cycles at 50% strain). These aerogels can be assembled into compressive solid‐state symmetric supercapacitors showing excellent area capacitance (109.4 mF cm–2 at 0.4 mA cm–2) and superior long cycle compression performance (88% after 5000 cycles at compressive strain of 50%). Furthermore, the aerogels reveal good linear sensitivity (S = 5.61 kPa–1) and accurately capture human bio‐signals as strain sensors. It is expected that such CNF/CNT/RGO carbon aerogels will provide a novel multifunctional platform for wearable electronics, electronic skin, and human motion monitoring.

Coaxial 3D printed anisotropic thermal conductive composite aerogel with aligned hierarchical porous carbon nanotubes and cellulose nanofibers

Thermal management materials are obtaining increasing research interest, due to the requirement on energy conservation and environment protection. However, the complex designs and energy-consuming manufacturing processes prohibit their wide spread practical account. 3D printing is an intriguing revolutionary technology in fabricating anisotropic thermal conductive materials because of its inherent virtues on directional additive manufacturing a complicated subject with designed microstructure. We demonstrate the coaxial 3D printing along with directional freezing processes to obtain anisotropic thermal conductive composite aerogel consisting of carbon nanotubes (CNTs) and cellulose nanofibers (CNFs). The as prepared composite aerogel, with the thermal conductive CNTs as inner layer, and the insulate CNFs as outer layer, presented remarkable anisotropic thermal conductivity with 0.025 W (m K)−1 in the axial direction and 0.302 W (m K)−1 in the radial direction. The Young’s modulus of the CNTs/CNFs composite aerogel was tested to be 10.91 MPa in the axial direction, and 2.62 MPa in the radial direction, respectively. The coaxial 3D printed CNTs/CNFs composite aerogel has great potential application in electronics, especially for those custom-tailored products and the related field.

Multifunctional Nanocellulose/Carbon Nanotube Composite Aerogels for High-Efficiency Electromagnetic Interference Shielding

Bio-based specialized components have emerged as a promising trend to limit the use of petroleum derivatives. Conversely, the current use of electronic systems has conditioned the emission of electromagnetic waves that interfere with high-precision devices and harm human health. Thus, robust, ultralight, and conductive nanocellulose-based aerogels paired with carbon nanotubes appear as an electromagnetic interference (EMI) shielding biomaterial to reduce the dispersion of microwaves emitted or received from a device. This study proposes a reliable aerogel system to deflect radiation by integrating TEMPO-oxidized cellulose nanofibrils, cationic cellulose nanocrystals, and sodium alginate, with carbon nanotubes at various concentrations. After inducing gelation, the aerogels were obtained by freeze drying. According to zeta potential and FTIR analysis data of nanocellulose, the aerogel frame was induced by electrostatic attraction and hydrogen bonds between the cellulosic matrix and the nanofillers. Finally, lightweight (density < 0.075 g/cm3), highly porous (porosity > 95.47%), conductive (up to 26.2 S/m), mechanically resistant, and EMI-protective aerogels were obtained, proving their potential to be used as green and lightweight shielding elements against electromagnetic radiation.

Fibrillation of well-formed conductive aerogel for soft conductors

Cellular-structured aerogels are usually formed by lyophilization with a slow freeze-drying process. However, there remains a challenge to improve the flexibility of a well-formed aerogel with cellular structures. In this study, cellular structural conductive polymer aerogels were fibrillated with the assistance of the post vapor annealing technique and a functional copolymer, polyethylene-block-poly (ethylene glycol) (PBP). The underlying mechanism lies in the thin walls of the cellular-structured aerogel transformed into fibers during the melting and flowing of PBP parts through ethylene glycol vapor annealing. Moreover, the PBP segments of polyethylene and polyethylene glycol (PEG) act as plasticizers and conductivity enhancers, improving the aerogel's flexibility and electrical conductivity. The fibrillated conductive polymer aerogels were used as sensing elements in strain sensors and electrodes in the triboelectric nanogenerator, demonstrating their potential in soft conductors.

An Ultralight Self-Powered Fire Alarm e-Textile Based on Conductive Aerogel Fiber with Repeatable Temperature Monitoring Performance Used in Firefighting Clothing.

Firefighting protective clothing is an essential equipment that can protect firefighters from burn injuries during the firefighting process. However, it is still a challenge to detect the damage of firefighting protective clothing at an early stage when firefighters are exposed to excessively high temperature in fire cases. Herein, an ultralight self-powered fire alarm electronic textile (SFA e-textile) based on conductive aerogel fiber that comprises calcium alginate (CA), Fe3O4 nanoparticles (Fe3O4 NPs), and silver nanowires (Ag NWs) was developed, which achieved ultrasensitive temperature monitoring and energy harvesting in firefighting clothing. The resulting SFA e-textile was integrated into firefighting protective clothing to realize wide-range temperature sensing at 100-400 °C and repeatable fire warning capability, which could timely transmit an alarm signal to the wearer before the firefighting protective clothing malfunctioned in extreme fire environments. In addition, a self-powered fire self-rescue location system was further established based on the SFA e-textile that can help rescuers search and rescue trapped firefighters in fire cases. The power in the self-powered fire location system was offered by an SFA e-textile-based triboelectric nanogenerator (TENG). This work provided a useful design strategy for the preparation of ultralight wearable temperature-monitoring SFA e-textile used in firefighting protective clothing.

Anisotropic conductive shape-memory aerogels as adaptive reprogrammable wearable electronics for accurate long-term pressure sensing

The reprogrammable shape-memory effect of the anistropic aerogel-based sensing electronics enables adaptive wearability, potentially ensuring accurate long-term physical monitoring without suppressing inherent excellent pressure-sensing performance.

Graphene-Anchored Conductive Polymer Aerogel Composite for the Electrocatalytic Detection of Hydrogen Peroxide and Bisphenol a

Graphene-Anchored Conductive Polymer Aerogel Composite for the Electrocatalytic Detection of Hydrogen Peroxide and Bisphenol a

Highly conductive CNT aerogel synthesizedviaan inert FC-CVD technique: a step towards a greener approach

The accumulation of hydrogen gas molecules generatedin situas a byproduct of chemical reactions enhances the reducing ambient conditions of the otherwise inert FC-CVD reactor which improves the quality of the CNTs.

Highly Elastic and Fatigue-Resistant Graphene-Wrapped Lamellar Wood Sponges for High-Performance Piezoresistive Sensors

Three-dimensional (3D) conductive aerogels with structural robustness and mechanical resilience are highly attractive for sensitive and stable pressure sensing. However, the fabrication of such 3D aerogels often relies on complicated bottom-up assembly processes that involve costly raw materials or intensive energy consumption or directly coating synthetic polymer sponges (e.g., polyurethane) with conductive materials, which may pose environmental concerns for their disposal. Herein, a simple and sustainable strategy is proposed to fabricate a reduced graphene oxide-coated wood sponge (RGO@WS) with a lamellar structure for high-performance piezoresistive sensors. The introduced RGO nanosheets endow the RGO@WS not only with high conductivity but also with high elasticity and excellent fatigue resistance. These features make it an ideal piezoresistive sensor with a high sensitivity of 0.32 kPa–1 (superior to most polymeric sponge-based sensors), high working stability over 10 000 cycles, and excellent sensing reproducibility at ultralow temperatures. Thanks to its prominent sensing performance, the RGO@WS-based sensor can serve as a wearable device for detecting human motions and physiological signals and allows for spatially resolved pressure mapping via integrating the sensors into a large-area sensing array. The developed highly elastic and fatigue-resistant RGO@WS represents a promising and sustainable alternative to the synthetic polymer-based piezoresistive sensors.

Fabrication and characterization of carbon aerogel/poly(glycerol-sebacate) patches for cardiac tissue engineering

Cardiovascular diseases (CVDs) are responsible for the major number of deaths around the world. Among these is heart failure after myocardial infarction whose latest therapeutic methods are limited to slowing the end-state progression. Numerous strategies have been developed to meet the increased demand for therapies regarding CVDs. This study aimed to establish a novel electrically conductive elastomer-based composite and assess its potential as a cardiac patch for myocardial tissue engineering. The electrically conductive carbon aerogels (CAs) used in this study were derived from waste paper as a cost-effective carbon source and they were combined with the biodegradable poly(glycerol-sebacate) (PGS) elastomer to obtain an electrically conductive cardiac patch material. To the best of our knowledge, this is the first report about the conductive composites obtained by the incorporation of CAs into PGS (CA-PGS). In this context, the incorporation of the CAs into the polymeric matrix significantly improved the elastic modulus (from 0.912 MPa for the pure PGS elastomer to 0.366 MPa for the CA-PGS) and the deformability (from 0.792 MPa for the pure PGS to 0.566 MPa for CA-PGS). Overall, the mechanical properties of the obtained structures were observed similar to the native myocardium. Furthermore, the addition of CAs made the obtained structures electrically conductive with a conductivity value of 65 × 10−3 S m−1 which falls within the range previously recorded for human myocardium. The in vitro cytotoxicity assay with L929 murine fibroblast cells revealed that the CA-PGS composite did not have cytotoxic characteristics. On the other hand, the studies conducted with H9C2 rat cardiac myoblasts revealed that final structures were suitable for MTE applications according to the successes in cell adhesion, cell proliferation, and cell behavior.

Scalable Fabrication of Ti3C2Tx MXene/RGO/Carbon Hybrid Aerogel for Organics Absorption and Energy Conversion.

High aspect ratio two-dimensional Ti3C2Tx MXene flakes with extraordinary mechanical, electrical, and thermal properties are ideal candidates for assembling elastic and conductive aerogels. However, the scalable fabrication of large MXene-based aerogels remains a challenge because the traditional preparation method relies on supercritical drying techniques such as freeze drying, resulting in poor scalability and high cost. Herein, the use of porous melamine foam as a robust template for MXene/reduced graphene oxide aerogel circumvents the volume shrinkage during its natural drying process. Through this approach, we were able to produce large size (up to 600 cm3) MXene-based aerogel with controllable shape. In addition, the aerogels possess an interconnected cellular structure and display resilience up to 70% of compressive strain. Some key features also include high solvent absorption capacity (∼50-90 g g-1), good photothermal conversion ability (an average evaporation rate of 1.48 kg m-2 h-1 for steam generation), and an excellent electrothermal conversion rate (1.8 kg m-2 h-1 at 1 V). More importantly, this passive drying process provides a scalable, convenient, and cost-effective approach to produce high-performance MXene-based aerogels, demonstrating the feasibility of commercial production of MXene-based aerogels toward practical applications.

A nanoporous Three-dimensional graphene aerogel doped with a carbon quantum Dot-TiO2 composite that exhibits superior activity for the catalytic photodegradation of organic pollutants

Three-dimensional (3D) graphene aerogel (3DGA) is an emerging photocatalyst support that imparts improved charge-carrier mobility. In this study, a 3DGA framework doped with carbon-quantum-dot-decorated TiO2 nanosheets (3DGA@CDs-TNs) is fabricated by a hydrothermal method. 3DGA@CDs-TNs is then applied as a catalyst to degrade organic pollutants in aqueous solutions. The degradation rates for Cong-red (CR, 120 mg L-1), Rhodamine B (RhB, 20 mg L-1), and colorless tetracycline (TC, 100 mg L-1) reach 98.7% (after 2 h), 97.6% (after 2 h), and 99.8% (after 40 min), respectively, under visible-light irritation, and these rates are much higher than those for CDs-TNs and 3DGA alone. Meanwhile, the dyed wastewater was collected to verify the practicability of 3DGA@CDs-TNs. These enhanced efficiencies arise from the unique 3DGA@CDs-TNs configuration, in which the conductive 3DGA aerogel acts as an effective electron mediator that connects the CDs-TNs composite fragments, providing channels for fast charge transfer. In addition, 3DGA@CDs-TNs also exhibits excellent stability during recycling experiments, confirming its durability and practicability.

Ultralight polypyrrole crosslinked nanofiber aerogel for highly sensitive piezoresistive sensor

Nanofiber aerogel is an ideal carrier for constructing high-sensitivity flexible piezoresistive sensors due to its abundant pore structure and excellent mechanical property. However, the reported nanofiber-based piezoresistive sensors generally need tedious high-temperature carbonization process to fabricate the 3D conductive network. Here, a simple, low-cost, and effective method is developed for constructing high-sensitivity all nanofiber-based piezoresistive sensor. The conductive nanofiber aerogel is prepared through freeze-drying method by using in-situ polymerized conductive polymer polypyrrole and electrospinning cellulose acetate nanofiber. Benefiting from the nanofiber skeleton and multistage pore structure, the obtained aerogel possesses an ultra-low volume density of 14.67 mg cm−3. Specifically, the unique nanofiber-based conductive pathways endow the aerogel with an ultra-high sensitivity up to 60.28 kPa−1 in a wide pressure range of 0 ~ 24 kPa. Meanwhile, the flexible nanofiber-based piezoresistive sensor also exhibit excellent cycling stability, which can withstand more than 13,000 cycles of compression. Furthermore, it shows great application potential as a flexible wearable sensor in human motion and health monitoring.

Metal Ion‐Induced Assembly of MXene Aerogels via Biomimetic Microtextures for Electromagnetic Interference Shielding, Capacitive Deionization, and Microsupercapacitors

AbstractScaling the synergistic properties of MXene nanosheets to microporous aerogel architectures requires effective strategies to overcome the nanosheet restacking without compromising MXene's advantageous properties. Traditional assembly approaches of 3D MXene aerogels normally involve external binders/templates and/or additional functionalization, which sacrifice the electrical conductivities and electrochemical activities of MXene aerogels. Herein, inspired by the hierarchal scale textures of Phrynosoma cornutum, a crumple‐textured Ti3C2Tx MXene platform is engineered to facilitate Mg2+‐induced assembly, enabling conformal formation of large‐area Mg2+‐MXene aerogels without polymeric binders. Through a doctor blading technique and freeze drying, the Mg2+‐MXene aerogels are produced with customized shapes/dimensions, featuring high surface area (140.5 m2 g−1), superior electrical conductivity (758.4 S m−1), and high robustness in water. The highly conductive MXene aerogels show their versatile applications from macroscale technologies (e.g., electromagnetic interference shielding and capacitive deionization (CDI)) to on‐chip electronics (e.g., quasi‐solid‐state microsupercapacitors (QMSCs)). As CDI electrodes, the Mg2+‐MXene aerogels exhibit high salt adsorption capacity (33.3 mg g−1) and long‐term operation reliability (over 30 cycles), showing a superb comparison with the literature. Also, the QMSCs with interdigitated Mg2+‐MXene aerogel electrodes demonstrate high areal capacitances (409.3 mF cm−2) with superior power density and energy density compared with other state‐of‐art QMSCs.

Thermal insulating, light-weight and conductive cellulose/aramid nanofibers composite aerogel for pressure sensing

Conductive nanocellulose aerogels have attracted significant attention in pressure sensing for wearable devices owing to lightweight, sustainability and good chemical stability. Limited by its flammability and weak mechanical properties, aramid nanofiber (ANF) was designed as reinforcement to overcome the shortcoming mentioned above. Herein, the unidirectional freeze casting method was proposed to fabricate nanocellulose/aramid nanofiber (CA) aerogel. Then, the CA/PPy (CAP) aerogel was obtained by using the oriented structure of CA aerogel as a template for inducing conductive polypyrrole (PPy) in-situ formation inside the composite aerogel. The conductive aerogel with the ordered microstructure exhibited the anisotropic mechanical properties and thermal conductivity. And it could withstand high temperature without any destruction phenomenon. Moreover, the aerogel sensor revealed high strain sensitivity and satisfactory electrochemical performance. Lightweight CAP aerogel with controllable alignment, sensitive sensing property and thermal stability is very promising in pressure sensor under some extreme conditions.