Diamond-Reinforced Al(H2PO4)3@Epoxy Hybrid Thermal Adhesive With Ultra-High Thermal Conductivity and Bonding Strength.

The miniaturization, integration, and increased power of electronic devices have exacerbated serious heat dissipation issues. Thermally conductive adhesives, which effectively transfer heat and firmly bond components, are critical for addressing these challenges. This paper innovatively proposed a composite comprising inorganic phosphate/alumina as a matrix and diamond as filler. The composite achieved an isotropic thermal conductivity (TC) of up to 18.96 W m-1 K-1, significantly surpassing existing reports while maintaining electrical insulation. First-principles calculations and experimental tests confirmed that the high TC of phosphate and excellent interface contact ensured efficient heat transfer. To optimize bonding performance, a modified-diamond/Al(H2PO4)3@epoxy hybrid composite is subsequently developed using an organic modification method. The unique hybrid structure, combining inorganic thermal pathways and an organic adhesive network, enabled the hybrid composite to simultaneously possess a high TC (3.23 W m-1 K-1) and strong adhesion (14.35 MPa). Compared to previous reports, the comprehensive performance of this hybrid thermally conductive adhesive is exceptionally remarkable. The superior heat dissipation capability of the hybrid thermal adhesive is demonstrated in chip cooling scenarios. This organic/inorganic hybrid approach offered a new direction for obtaining advanced thermal interface materials, demonstrating significant application potential in chip soldering, packaging, and heat dissipation.

Novel Conductive Polymer Composite PEDOT:PSS/Bovine Serum Albumin for Microbial Bioelectrochemical Devices.

A novel conductive composite based on PEDOT:PSS, BSA, and Nafion for effective immobilization of acetic acid bacteria on graphite electrodes as part of biosensors and microbial fuel cells has been proposed. It is shown that individual components in the composite do not have a significant negative effect on the catalytic activity of microorganisms during prolonged contact. The values of heterogeneous electron transport constants in the presence of two types of water-soluble mediators were calculated. The use of the composite as part of a microbial biosensor resulted in an electrode operating for more than 140 days. Additional modification of carbon electrodes with nanomaterial allowed to increase the sensitivity to glucose from 1.48 to 2.81 µA × mM-1 × cm-2 without affecting the affinity of bacterial enzyme complexes to the substrate. Cells in the presented composite, as part of a microbial fuel cell based on electrodes from thermally expanded graphite, retained the ability to generate electricity for more than 120 days using glucose solution as well as vegetable extract solutions as carbon sources. The obtained data expand the understanding of the composition of possible matrices for the immobilization of Gluconobacter bacteria and may be useful in the development of biosensors and biofuel cells.

Highly Thermally Conductive Aramid Nanofiber Composite Films with Synchronous Visible/Infrared Camouflages and Information Encryption.

The development of highly thermally conductive composites that combine visible light/infrared camouflage and information encryption has been endowed with great significance in facilitating the application of 5G communication technology in military fields. This work uses aramid nanofibers (ANF) as the matrix, hetero-structured silver nanowires@boron nitride nanosheets (AgNWs@BNNS) prepared by in situ growth as fillers, which are combined to fabricate sandwich structured thermally conductive and electrically insulating (BNNS/ANF)-(AgNWs@BNNS)-(BNNS/ANF) (denoted as BAB) composite films by "filtration self-assembly, air spraying, and hot-pressing" method. When the mass ratio of AgNWs@BNNS to BNNS is 1 : 1 and the total mass fraction is 50 wt %, BAB composite film has the maximum in-plane thermal conductivity coefficient (λ∥ of 10.36 W/(m ⋅ K)), excellent electrical insulation (breakdown strength and volume resistivity of 41.5 kV/mm and 1.21×1015â€…Ω â‹… cm, respectively) and mechanical properties (tensile strength of 170.9 MPa). 50 wt % BAB composite film could efficiently reduce the equilibrium temperature of the central processing unit (CPU) working at full power, resulting in 7.0 °C lower than that of the CPU solely integrated with ANF directly. In addition, BAB composite film boasts adaptive visible light/infrared dual camouflage properties on cement roads and jungle environments, as well as the function of fast encryption of QR code information within 24 seconds.

Printed Directional Bending Sensor with High Sensitivity and Low Hysteresis for Human Motion Detection and Soft Robotic Perception.

We present a high-performance flexible bending strain sensor for directional motion detection of human hands and soft robotic grippers. The sensor was fabricated using a printable porous conductive composite composed of polydimethylsiloxane (PDMS) and carbon black (CB). The utilization of a deep eutectic solvent (DES) in the ink formulation induced a phase segregation between the CB and PDMS and led to a porous structure inside the printed films after being vapored. This simple and spontaneously formed conductive architecture provided superior directional bend-sensing characteristics compared to conventional random composites. The resulting flexible bending sensors displayed high bidirectional sensitivity (gauge factor of 45.6 under compressive bending and 35.2 under tensile bending), negligible hysteresis, good linearity (>0.99), and excellent bending durability (over 10,000 cycles). The multifunctional applications of these sensors, including human motion detection, object-shape monitoring, and robotic perceptions, are demonstrated as a proof-of-concept.

Multifunctional Thermally Conductive Composite Films Based on Fungal Tree-like Heterostructured Silver Nanowires@Boron Nitride Nanosheets and Aramid Nanofibers.

Thermal conduction for electronic equipment has grown in importance in light of the burgeoning of 5G communication. It is imperatively desired to design highly thermally conductive fillers and polymer composite films with prominent Joule heating characteristics and extensive mechanical properties. In this work, "solvothermal & in situ growth" method is carried out to prepare "Fungal tree"-like hetero-structured silver nanowires@boron nitride nanosheet (AgNWs@BNNS) thermally conductive fillers. The thermally conductive AgNWs@BNNS/ANF composite films are obtained by the method of "suction filtration self-assembly and hot-pressing". When the mass fraction of AgNWs@BNNS is 50 wt%, AgNWs@BNNS/ANF composite film presents the optimal thermal conductivity coefficient of 9.44 W/(m ⋅ K) and excellent tensile strength of 136.6 MPa, good temperature-voltage response characteristics, superior electrical stability and reliability, which promise a wide application potential in 5G electronic devices.

Electric-Field-Induced Alignment of Functionalized Carbon Nanotubes Inside Thermally Conductive Liquid Crystalline Polyimide Composite Films.

The positive liquid crystals, 4'-heptyl-4-biphenylcarbonitrile (7CB), are used to functionalize carbon nanotubes (LC-CNT), which can be aligned in the liquid crystalline polyimide (LC-PI) matrix under an alternating electric field to fabricate the thermally conductive LC-CNT/LC-PI composite films. The efficient establishment of thermal conduction pathways in thermally conductive LC-CNT/LC-PI composite films with a low amount of LC-CNT is achieved through the oriented alignment of LC-CNT within the LC-PI matrix. When the mass fraction of LC-CNT is 15 wt %, the in-plane thermal conductivity coefficient (λ∥ ) and the through-plane thermal conductivity coefficient (λ⊥ ) of the LC-CNT/LC-PI composite films reach 4.02 W/(m ⋅ K) and 0.55 W/(m⋅K), which are 90.5 % and 71.9 % higher than those of the intrinsically thermally conductive LC-PI films respectively, also 28.8 % and 5.8 % higher than those of the CNT/LC-PI composite films respectively. Meanwhile, the thermally conductive LC-CNT/LC-PI composite films also possess excellent mechanical and heat resistance properties. The Young's modulus and the heat resistance index are 2.3 GPa and 297.7 °C, respectively, which are higher than the intrinsically thermally conductive LC-PI films and the thermally conductive CNT/LC-PI composite films under the same amount of CNT.

Recent Development of Multifunctional Sensors Based on Low-Dimensional Materials.

With the demand for accurately recognizing human actions and environmental situations, multifunctional sensors are essential elements for smart applications in various emerging technologies, such as smart robots, human-machine interface, and wearable electronics. Low-dimensional materials provide fertile soil for multifunction-integrated devices. This review focuses on the multifunctional sensors for mechanical stimulus and environmental information, such as strain, pressure, light, temperature, and gas, which are fabricated from low-dimensional materials. The material characteristics, device architecture, transmission mechanisms, and sensing functions are comprehensively and systematically introduced. Besides multiple sensing functions, the integrated potential ability of supplying energy and expressing and storing information are also demonstrated. Some new process technologies and emerging research areas are highlighted. It is presented that optimization of device structures, appropriate material selection for synergy effect, and application of piezotronics and piezo-phototronics are effective approaches for constructing and improving the performance of multifunctional sensors. Finally, the current challenges and direction of future development are proposed.

3D-printed electrodes using graphite/carbon nitride/polylactic acid composite material: A greener platform for detection of amaranth dye in food samples.

The production of sustainable materials with properties aimed at the additive manufacturing of electrochemical sensors has gained prestige in the scientific scenario. Here, a novel lab-made composite material using graphite (G) and carbon nitride (C3N4) embedded into polylactic acid (PLA) biopolymer is proposed to produce 3D-printed electrodes. PLA offers printability and mechanical stability in this composition, while G and C3N4 provide electrical properties and electrocatalytic sites, respectively. Characterizations by Raman and infrared spectroscopies and Energy Dispersive X-rays indicated that the G/C3N4/PLA composite was successfully obtained, while electron microscopy images revealed non-homogeneous rough surfaces. Better electrochemical properties were achieved when the G/C3N4/PLA proportion (35:5:60) was used. As a proof of concept, amaranth (AMR), a synthetic dye, was selected as an analyte, and a fast method using square wave voltammetry was developed. Utilizing the 3D-printed G/C3N4/PLA electrode, a more comprehensive linear range (0.2 to 4.2 µmol/L), a 5-fold increase in sensitivity (9.83 µmol-1 L µA), and better limits of detection (LOD = 0.06 µmol/L) and quantification (LOQ = 0.18 µmol/L) were achieved compared to the G/PLA electrode. Samples of jelly, popsicles, isotonic drinks, and food flavoring samples were analyzed, and similar results to those obtained by UV-vis spectrometry confirmed the method's reliability. Therefore, the described sensor is a simple, cost-effective alternative for assessing AMR in routine food analysis.

3D Printing of Anisotropic Piezoresistive Pressure Sensors for Directional Force Perception.

Anisotropic pressure sensors are gaining increasing attention for next-generation wearable electronics and intelligent infrastructure owing to their sensitivity in identifying different directional forces. 3D printing technologies have unparalleled advantages in the design of anisotropic pressure sensors with customized 3D structures for realizing tunable anisotropy. 3D printing has demonstrated few successes in utilizing piezoelectric nanocomposites for anisotropic recognition. However, 3D-printed anisotropic piezoresistive pressure sensors (PPSs) remain unexplored despite their convenience in saving the poling process. This study pioneers the development of an aqueous printable ink containing waterborne polyurethane elastomer. An anisotropic PPS featuring tailorable flexibility in macroscopic 3D structures and microscopic pore morphologies is created by adopting direct ink writing 3D printing technology. Consequently, the desired directional force perception is achieved by programming the printing schemes. Notably, the printed PPS demonstrated excellent deformability, with a relative sensitivity of 1.22 (kPa*wt. %)-1 over a substantial pressure range (2.8 to 8.1 kPa), approximately fivefold than that of a state-of-the-art carbon-based PPS. This study underscores the versatility of 3D printing in customizing highly sensitive anisotropic pressure sensors for advanced sensing applications that are difficult to achieve using conventional measures.

Bioinspired Functional Composites for Enhanced Thermally Conductivity via Fractal-Growth CuNP Fillers.

Thermal conduction for electronic devices has attracted extensive attention in light of the development of 5G communication. Thermally conductive materials with high thermal conductivity and extensive mechanical flexibility are extremely desirable in practical applications. However, the construction of efficient interconnected conductive pathways and continuous conductive networks is inadequate for either processing or actual usage in existing technologies. In this work, spherical copper nanoparticles (S-CuNPs) and urchin-inspired fractal-growth CuNPs (U-CuNPs), thermally conductive metal fillers induced by ionic liquids, were fabricated successfully through the electrochemical deposition method. Compared to S-CuNPs, the U-CuNPs shows larger specific surface contact area, thus making it easier to build a continuous conductive pathway network in the corresponding U-CuNPs/liquid silicone rubber (LSR) thermally conductive composites. The optimal loading of CuNP fillers was determined by evaluating the rheological performance of the prepolymer and the mechanical properties and thermal conductivity performances of the composites. When the filler loading is 150 phr, the U-CuNPs/LSR produces optimal mechanical properties (e.g., tensile strength and modulus), thermal conductivity (above 1000% improvement compared to pure LSR), and heating/cooling efficiency. The enhanced thermal conductivity of U-CuNPs/LSR was also confirmed through the finite element analysis (FEA) overall temperature distribution, indicating that U-CuNPs with larger specific surface contact areas exhibit more advantages in forming a continuous network in composites than S-CuNPs, making U-CuNPs/LSR a promising and competitive alternative to traditional flexible thermally interface materials.

Fabrication of Temperature Sensors with High-Performance Uniformity through Thermal Annealing.

It is considered to be of great significance to monitor human health and track the effect of drugs by measuring human temperature mapping through flexible temperature sensors. In this work, we found that the thermal annealing of flexible temperature sensors based on graphite-acrylate copolymer composites can not only improve the temperature coefficient of resistance (TCR) values of the devices, but also greatly improve the uniformity of the performance of the devices prepared in parallel. The best results were obtained when the devices were annealed at 100 °C, which is believed to be due to the rearrangement of graphite particles to generate more uniform and numerous conductive channels within the conductive composite. We believe this finding might promote the practical development of flexible temperature sensors in body temperature sensing for health maintenance and medical applications.

Development of 3D-Printed, Biodegradable, Conductive PGSA Composites for Nerve Tissue Regeneration.

Nerve conduits are used to reconnect broken nerve bundles and provide protection to facilitate nerve regeneration. However, the low degradation rate and regeneration rate, as well as the requirement for secondary surgery are some of the most criticized drawbacks of existing nerve conduits. With high processing flexibility from the photo-curability, poly (glycerol sebacate) acrylate (PGSA) is a promising material with tunable mechanical properties and biocompatibility for the development of medical devices. Here, polyvinylpyrrolidone (PVP), silver nanoparticles (AgNPs), and graphene are embedded in biodegradable PGSA matrix. The polymer composites are then assessed for their electrical conductivity, biodegradability, three-dimensional-printability (3D-printability), and promotion of cell proliferation. Through the four-probe technique, it is shown that the PGSA composites are identified as highly conductive in swollen state. Furthermore, biodegradability is evaluated through enzymatic degradation and facilitated hydrolysis. Cell proliferation and guidance are significantly promoted by three-dimensional-printed microstructures and electrical stimulation on PGSA composites, especially on PGSA-PVP. Hence, microstructured nerve conduits are 3D-printed with PGSA-PVP. Guided cell growth and promoted proliferation are subsequently demonstrated by Schwann cell culture combined with electrical stimulation. Consequently, 3D-printed nerve conduits fabricated with PGSA composites hold great potential in nerve tissue regeneration through electrical stimulation.

Highly Aligned Cellulose/Polypyrrole Composite Nanofibers via Electrospinning and In Situ Polymerization for Anisotropic Flexible Strain Sensor.

Flexible strain sensors have recently attracted great attention due to their promising applications in human motion detection, healthcare monitoring, human-machine interfaces, and so forth. However, traditional uniaxial strain sensors can only detect strain in a single direction. Herein, an anisotropic flexible strain sensor is fabricated based on conductive and highly aligned cellulose composite nanofibers, via facile electrospinning cellulose acetate, deacetylation, and in situ polymerization of pyrrole, to detect complex multidimensional strains. Benefiting from the unique well-ordered structure of conductive composite nanofibers, the obtained strain sensor shows extraordinary anisotropic sensing performance with a sensitivity of 0.73 and 0.01 for the tensile applied perpendicular and parallel to the nanofiber alignment, respectively. The sensor also exhibits outstanding durability (2000 cycles) due to the strong hydrogen bonding between cellulose nanofibers and polypyrrole. Moreover, the flexible strain sensors exhibit promising potentials for application in motion detection, as demonstrated by the detection of various joint movements in the human body.

Soft, adhesive and conductive composite for electroencephalogram signal quality improvement.

Since electroencephalogram (EEG) is a very small electrical signal from the brain, it is very vulnerable to external noise or motion artifact, making it difficult to measure. Therefore, despite the excellent convenience of dry electrodes, wet electrodes have been used. To solve this problem, self-adhesive and conductive composites using carbon nanotubes (CNTs) in adhesive polydimethylsiloxane (aPDMS), which can have the advantages of both dry and wet electrodes, have been developed by mixing them uniformly with methyl group-terminated PDMS. The CNT/aPDMS composite has a low Young's modulus, penetrates the skin well, has a high contact area, and excellent adhesion and conductivity, so the signal quality is enhanced. As a result of the EEG measurement test, although it was a dry electrode, results comparable to those of a wet electrode were obtained in terms of impedance and motion noise. It also shows excellent biocompatibility in a human fibroblast cell test and a week-long skin reaction test, so it can measure EEG with high signal quality for a long period of time.

Printed Composite Film with Microporous/Micropyramid Hybrid Conductive Architecture for Multifunctional Flexible Force Sensors.

Porous structures and micropatterning surfaces play a crucial role in the development of highly sensitive force sensors. However, achieving these two conductive architectures typically requires the synthesis of complex materials and expensive manufacturing processes. In this study, we introduce a novel conductive composite film featuring a microporous/micropyramid hybrid conductive architecture, which is achieved through a straightforward process of materials mixing and one-step screen printing. By utilizing a deep eutectic solvent in the ink component, micropores are induced in the printed composite, while the mesh of the screen mask acts as a template, resulting in a micropyramid film surface. We have successfully realized highly sensitive flexible force sensors (0.15 kPa-1) with multifunctional capabilities for perceiving normal force and shear force.

Three-Dimensionally Printed Expandable Structural Electronics Via Multi-Material Printing Room-Temperature-Vulcanizing (RTV) Silicone/Silver Flake Composite and RTV.

Three-dimensional (3D) printing has various applications in many fields, such as soft electronics, robotic systems, biomedical implants, and the recycling of thermoplastic composite materials. Three-dimensional printing, which was only previously available for prototyping, is currently evolving into a technology that can be utilized by integrating various materials into customized structures in a single step. Owing to the aforementioned advantages, multi-functional 3D objects or multi-material-designed 3D patterns can be fabricated. In this study, we designed and fabricated 3D-printed expandable structural electronics in a substrateless auxetic pattern that can be adapted to multi-dimensional deformation. The printability and electrical conductivity of a stretchable conductor (Ag-RTV composite) were optimized by incorporating a lubricant. The Ag-RTV and RTV were printed in the form of conducting voxels and frame voxels through multi-nozzle printing and were arranged in a negative Poisson's ratio pattern with a missing rib structure, to realize an expandable passive component. In addition, the expandable structural electronics were embedded in a soft actuator via one-step printing, confirming the possibility of fabricating stable interconnections in expanding deformation via a missing rib pattern.

Inhibited astrocytic differentiation in neural stem cell-laden 3D bioprinted conductive composite hydrogel scaffolds for repair of spinal cord injury.

The emergence of three-dimensional (3D) bioprinting technology has attracted ever-increasing attention in engineered tissue fabrication for stem cell-based tissue repair. However, the in vivo performance of transplanted stem cells in the tissue engineering scaffolds is still a major concern for regenerative medicine researches. Especially for neural stem cell (NSC) transplantation, the uncontrollable differentiation of the NSCs in host often leads to a poor therapeutic effect in nerve tissue repair, such as spinal cord injury (SCI) repair. To address this issue, we have fabricated a conductive composite hydrogel (CCH) scaffold loading with NSCs by 3D bioprinting, for delivering the NSCs to injured spinal cord and repairing the propriospinal nerve circuit. In our strategy, a novel conductive polymer (PEDOT:CSMA,TA) was synthesized and introduced into a photocrosslinkable gelatin/polyethylene glycol physical-gel matrix, thereby forming a composite bioink with well shear-thinning and self-healing properties. The composite bioink we prepared was then printed into the NSC-laden CCH scaffold with high shape fidelity and similar physicochemical properties to native spinal cord tissues. The NSCs encapsulated in the bioprinted CCH scaffold extended their neurites to form superior physical contact with the neighboring cells as well as the electroconductive matrix, and maintained a predominant in vivo neuronal differentiation, accompanying with few astrocytic production in the lesion area after transplantation into the SCI sites. As a result, the removal of glial scar tissues and the regeneration of well-developed nerve fibres sequentially happened, which not only facilitated nerve tissue development, but also accelerated locomotor function recovery in the SCI rats. By exploring the application of conductive biomaterials in stem cell-based SCI therapy, this work represents a feasible, new approach to precisely construct tissue engineering scaffolds for stem cell-based therapy in traumatic SCI and other nervous system diseases.

Effect of Carbon Fibres on Electromagnetic-Interference-Shielding Properties of Geopolymer Composites.

Many of the construction materials available are known to cause a drastic level of damage to the environment during their manufacturing stages. Hence, many researchers have attempted to formulate construction materials that are more environmentally friendly. Additionally, the rise in wireless communications in recent decades has seen a rapid increase in electromagnetic pollution and interference, which affects the functionality of sensitive electronic devices. This research is focused on fabricating a more sustainable construction material that could prevent electromagnetic interference for electronic devices housed inside. Carbon fibres of three different lengths were added in four variations to a geopolymer control mix to study their effect on electromagnetic interference shielding. The results showed that the amount of shielding produced by these composites increases with carbon fibre length and quantity. Morphological analyses showed that the interconnectivity of the fibres plays a crucial role in having a high level of shielding. While the flexural strength showed an improvement with the addition of carbon fibre, the compressive strength showed a slight reduction with the increase in carbon fibre length. The optimal level of shielding was produced by the specimen containing 0.7% of 12 mm carbon fibre, which was the maximum amount of fibre of any length used in this study; the optimal level of shielding generated was 43.43 dB within the frequency range of 30 MHz to 1.5 GHz.

Development of electrically conductive hybrid composites with a poly(lactic acid) matrix, with enhanced toughness for injection molding, and material extrusion-based additive manufacturing.

In this study, we developed electrically conductive nano- and hybrid composites with a poly(lactic acid) (PLA) matrix for different melt processing technologies. We used short carbon fiber and multi-walled carbon nanotube reinforcements to enhance electric conductivity. We prepared the composite compounds with twin-screw extrusion; then the compounds were processed via injection molding and fused filament fabrication. We showed that electric conductivity only slightly increased by when only carbon nanotubes were added to the PLA matrix. However, when carbon fibers were added to the nanocomposites, the higher shear during melt mixing helped the uniform dispersion of the carbon nanotubes, resulting in a highly conductive reinforcement network in the composite. On the other hand, the hybrid reinforcement resulted in higher viscosity, making melt processing difficult and the material also became more brittle. Therefore, we added an oligomeric lactic acid plasticizer to the hybrid composites, and produced specimens by injection molding and 3D printing. The tensile strength increased by 140% and the elongation at break increased by 56%, and at the same time, the electrical conductivity of the material remained at a high level.

Electromechanical Performance of Strain Sensors Based on Viscoelastic Conductive Composite Polymer Fibers.

Flexible conductive polymer composite (CPC) fibers that show large changes in resistance with deformation have recently gained much attention as strain-sensing components for future wearable electronics. However, the electrical resistance of these materials decays with time during dynamic cyclic loading, a deformation performed to simulate their real application as strain sensors. Despite the extensive research on CPC fibers, the mechanism leading to this decay in the electromechanical response under repetitive cycles remains unreported. Herein, this behavior is investigated using fiber-based strain sensors wet spun from thermoplastic polyurethane (TPU) consisting of a carbonaceous hybrid conductive filler system of carbon black (CB) and carbon nanotubes (CNTs). We found electrical viscosity to predict the observed electromechanical resistance decay. This implies that cycling these materials enables the relaxation of both the polymer chains and the conductive network. In addition, the resulting piezoresistive fibers are sensitive to deformation in the region of low strain (gauge factor of 6.0 within 3.0% strain), remain conductive under 280.5% deformation, and are stable for more than 2000 cycles. Finally, we demonstrate the potential of TPU/CB-CNT fibers as strain sensors for monitoring human motion.