Adding graphite nanoplatelets (GNP) into silicone rubber (SR) composites have shown significant potential for wearable electronics, where electrical, mechanical, and tribological properties play a ...crucial role. This study investigates the effects of incorporating graphite nanoplatelets (GNP) into SR composites and their impact on these key properties. Solution mixing of SR and GNP was performed to confirm good dispersion of the GNP within the SR matrix. The results showed improved tensile strength and modulus while stabilizing the flexibility and stretchability required for wearable electronics. For example, the tensile strength of the composites was 0.86 MPa (control) and increased to 1.18 MPa (5 part per hundred rubber phr GNP), and 1.55 MPa (15 phr GNP). Similarly, the stretchability was 177 % (control) and increased to 190 % (5 phr GNP), and 184 % (15 phr GNP). Moreover, the electro‐mechanical tests were studied and the output voltage for the samples were 0.28 milli‐volt (mV) (5 phr GNP), and 0.31 mV (15 phr GNP). Similarly, the output voltage generation was studied through human motions. The results obtained from these biomechanical motions such as thumb pressing were 0.7 mV (5 phr GNP), and 2.7 mV (15 phr GNP). The study finds the potential of GNP‐SR composites as multifunctional materials such as wearable electronics. Overall, this research guides the development of advanced wearable devices, soft robotics, and bio‐inspired electronics with improved performance and durability.
Different Configurations of Wearable Electronic Systems.
Graphene, a two-dimensional nanosheet, is composed of carbon species (sp2 hybridized carbon atoms) and is the center of attention for researchers due to its extraordinary physicochemical (e.g., ...optical transparency, electrical, thermal conductivity, and mechanical) properties. Graphene can be synthesized using top-down or bottom-up approaches and is used in the electronics and medical (e.g., drug delivery, tissue engineering, biosensors) fields as well as in photovoltaic systems. However, the mass production of graphene and the means of transferring monolayer graphene for commercial purposes are still under investigation. When graphene layers are stacked as flakes, they have substantial impacts on the properties of graphene-based materials, and the layering of graphene obtained using different approaches varies. The determination of number of graphene layers is very important since the properties exhibited by monolayer graphene decrease as the number of graphene layer per flake increases to 5 as few-layer graphene, 10 as multilayer graphene, and more than 10 layers, when it behaves like bulk graphite. Thus, this review summarizes graphene developments and production. In addition, the efficacies of determining the number of graphene layers using various characterization methods (e.g., transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectra and mapping, and spin hall effect-based methods) are compared. Among these methods, TEM and Raman spectra were found to be most promising to determine number of graphene layers and their stacking order.
The flexible silicone elastomer‐conductive composite was developed with enhanced energy harvesting and strain sensing. A hybrid nanofiller system with multi‐walled carbon nanotubes (MWCNTs) and ...titanium (IV) carbide (TiC) was used as reinforcing agents for the elastomer. The 4 MWCNT +5 TiC composite has 1.34 MPa tensile strength, 136.85% higher than unfilled silicone rubber (SR) matrix. The unfilled sample has a 1.558 MPa compressive modulus, while 4 MWCNT +5 TiC has 3.87 MPa. The machine and finger presses were utilized to test the energy harvesting of the composite. With greater cyclic stability, the 4 MWCNT +5 TiC sample performed exceptionally well in the machine press in the output voltage range of around 120 mV. Among the thumb presses, 2 MWCNT +5 TiC yielded the best results, with a voltage of about 100 mV. The 3 MWCNT +5 TiC sample produced 9044% more energy than the single filler 3 phr MWCNT sample from our previous work. Higher MWCNT content enhanced composite stiffness, making finger pressing harder and decreasing energy output. The strain sensing test on the 4 MWCNT +5 TiC composite showed high gauge factors (GF = 7.532 and 23.944) and good linearity (R2 = 0.909 and 0.939) over a strain range of Δε = 0%–14% and 14%–22%. Silicone composites' mechanical, energy harvesting, and strain sensing performance improved greatly with the MWCNT and TiC hybrid fillers. These composites could be used in self‐powered wearable electronics, machine or structural deformation monitoring, and human motion sensing.
Highlights
A stretchable device was developed with improved energy harvesting and strain sensing.
Rubber composites were fabricated from MWCNTs, TiC hybrid fillers, and SR matrix.
The energy harvesting was 9044% higher for hybrid filler compared to MWCNT as the only filler.
Robust strain sensing properties with a gauge factor of 23.9, linearity of 0.91, and relaxation time of 0.1 s.
The final composites are useful for self‐powered wearable electronics, health monitoring, and human motion sensing.
Smart configurations of the composites used for energy generation and strain sensing.
The use of secondary reinforcing fillers such as graphene or multi‐wall carbon nanotube (CNT) for improving mechanical properties is an effective strategy to obtain high performance ...magneto‐rheological elastomers (MREs). Therefore, MREs were prepared via solution mixing of room‐temperature‐vulcanized silicone rubber (RTV‐SR) and iron oxide (Fe3O4), and hybridized with iron wire, Few‐layer graphene (FLG), and CNT as secondary nanofillers. The isotropic mechanical properties were studied through compressive tests, and their compressive moduli and reinforcing factors were determined. From these studies, it was found that CNT‐based hybrid MREs show the highest compressive mechanical properties. For example, at 80 per hundred parts of rubber (phr), the compressive modulus was 3.5 MPa (RTV‐SR/Fe3O4), 4.1 MPa (RTV‐SR/Fe3O4‐FLG), 5.5 MPa (RTV‐SR/Fe3O4‐CNT), and 3.7 MPa (RTV‐SR/Fe3O4‐iron wires). A nanofiller with higher aspect ratio (CNT), has a strong effect on the isotropic mechanical properties, whereas a lower aspect ratio nanofiller (FLG) has a greater effect on magnetic sensitivity. Although iron wires with lower specific surface areas can only improve the mechanical properties slightly, they can improve the magnetic sensitivity of MREs because of its stronger magnetic behavior.
In this work, MREs were prepared using RTV silicone rubber, iron oxide and their hybrids. Iron wire, few‐layer graphene (FLG), and carbon nanotube (CNT) were used as secondary reinforcing fillers. Isotropic and Anisotropic mechanical properties were studied in presence and absence of magnetic field. Secondary reinforcing fillers such as CNT with high aspect ratio shows highest reinforcing ability while FLG with lower aspect ratio shows higher magnetic sensitivity.
Nitrogen (N) is a key macronutrient essential for plant growth, and its availability has a strong influence on crop development. The application of synthetic N fertilizers on crops has increased ...substantially in recent decades; however, the applied N is not fully utilized due to the low N use efficiency of crops. To overcome this limitation, it is important to understand the genome-wide responses and functions of key genes and potential regulatory factors in N metabolism.
Here, we characterized changes in the rice (Oryza sativa) transcriptome, including genes, newly identified putative long non-coding RNAs (lncRNAs), and microRNAs (miRNAs) and their target mRNAs in response to N starvation using four different transcriptome approaches. Analysis of rice genes involved in N metabolism and/or transport using strand-specific RNA-Seq identified 2588 novel putative lncRNA encoding loci. Analysis of previously published RNA-Seq datasets revealed a group of N starvation-responsive lncRNAs showing differential expression under other abiotic stress conditions. Poly A-primed sequencing (2P-Seq) revealed alternatively polyadenylated isoforms of N starvation-responsive lncRNAs and provided precise 3' end information on the transcript models of these lncRNAs. Analysis of small RNA-Seq data identified N starvation-responsive miRNAs and down-regulation of miR169 family members, causing de-repression of NF-YA, as confirmed by strand-specific RNA-Seq and qRT-PCR. Moreover, we profiled the N starvation-responsive down-regulation of root-specific miRNA, osa-miR444a.4-3p, and Degradome sequencing confirmed MADS25 as a novel target gene.
In this study, we used a combination of multiple RNA-Seq analyses to extensively profile the expression of genes, newly identified lncRNAs, and microRNAs in N-starved rice roots and shoots. Data generated in this study provide an in-depth understanding of the regulatory pathways modulated by N starvation-responsive miRNAs. The results of comprehensive, large-scale data analysis provide valuable information on multiple aspects of the rice transcriptome, which may be useful in understanding the responses of rice plants to changes in the N supply status of soil.
Graphite nanoplatelet (GNP) flakes have attracted attention for the production of polymeric nanocomposites owing to their excellent mechanical, thermal, and electrical properties. In this work, the ...impact of three grades of GNP flakes with different surface area on the properties of room‐temperature vulcanized silicone rubber (RTV‐SR) nanocomposites was analyzed. The surface area was determined by the Brunauer–Emmett–Teller (BET) method using N2 adsorption isotherms. The BET analysis showed that the GNP grades had BET surface areas of 422, 295, and 123 m2/g. Nanocomposites based on the three grades of GNP flakes with different surface area and RTV‐SR were prepared using the solution‐casting process. Mechanical analysis of the samples showed that the compressive modulus increased from 3.8 MPa (0 phr) to 4.4, 4.34, and 5.26 MPa at the filler loading of 15 phr of GNPs with 422, 295, and 123 m2/g, respectively. In addition, the fracture strain of the nanocomposites increased from 116% (0 phr) to 228%, 198%, and 151% in the samples with 422, 295, and 123 m2/g, respectively, at the filler loading of 15 phr GNP.
Present work demonstrates composites based on RTV silicone rubber and graphite nanoplatelets with different BET surface areas of 422, 295, and 123 m2/g. Then, their co‐relation with mechanical properties was studied.
It is advantageous to construct a dielectric metasurface in silicon due to its compatibility with cost-effective, mature processes for complementary metal-oxide-semiconductor devices. However, ...high-quality crystalline-silicon films are difficult to grow on foreign substrates. In this work, we propose and realize highly efficient structural color filters based on a dielectric metasurface exploiting hydrogenated amorphous silicon (a-Si:H), known to be lossy in the visible regime. The metasurface is comprised of an array of a-Si:H nanodisks embedded in a polymer, providing a homogeneously planarized surface that is crucial for practical applications. The a-Si:H nanodisk element is deemed to individually support an electric dipole (ED) and magnetic dipole (MD) resonance via Mie scattering, thereby leading to wavelength-dependent filtering characteristics. The ED and MD can be precisely identified by observing the resonant field profiles with the assistance of finite-difference time-domain simulations. The completed color filters provide a high transmission of around 90% in the off-resonance band longer than their resonant wavelengths, exhibiting vivid subtractive colors. A wide range of colors can be facilitated by tuning the resonance by adjusting the structural parameters like the period and diameter of the a-Si:H nanodisk. The proposed devices will be actively utilized to implement color displays, imaging devices, and photorealistic color printing.
Without fillers, rubber types such as silicone rubber exhibit poor mechanical, thermal, and electrical properties. Carbon black (CB) is traditionally used as a filler in the rubber matrix to improve ...its properties, but a high content (nearly 60 per hundred parts of rubber (phr)) is required. However, this high content of CB often alters the viscoelastic properties of the rubber composite. Thus, nowadays, nanofillers such as graphene (GE) and carbon nanotubes (CNTs) are used, which provide significant improvements to the properties of composites at as low as 2–3 phr. Nanofillers are classified as those fillers consisting of at least one dimension below 100 nanometers (nm). In the present review paper, nanofillers based on carbon nanomaterials such as GE, CNT, and CB are explored in terms of how they improve the properties of rubber composites. These nanofillers can significantly improve the properties of silicone rubber (SR) nanocomposites and have been useful for a wide range of applications, such as strain sensing. Therefore, carbon-nanofiller-reinforced SRs are reviewed here, along with advancements in this research area. The microstructures, defect densities, and crystal structures of different carbon nanofillers for SR nanocomposites are characterized, and their processing and dispersion are described. The dispersion of the rubber composites was reported through atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The effect of these nanofillers on the mechanical (compressive modulus, tensile strength, fracture strain, Young’s modulus, glass transition), thermal (thermal conductivity), and electrical properties (electrical conductivity) of SR nanocomposites is also discussed. Finally, the application of the improved SR nanocomposites as strain sensors according to their filler structure and concentration is discussed. This detailed review clearly shows the dependency of SR nanocomposite properties on the characteristics of the carbon nanofillers.
Zinc oxide performs as the best cure activator in sulfur-based vulcanization of rubber, but it is regarded as a highly toxic material for aquatic organisms. Hence, the toxic cure activator should be ...replaced by a non-toxic one. Still, there is no suitable alternative industrially. However, binary activators combining ZnO and another metal oxide such as MgO can largely reduce the level of ZnO with some improved benefits in the vulcanization of rubber as investigated in this research. Curing, mechanical, and thermal characteristics were investigated to find out the suitability of MgO in the vulcanization of rubber. Curing studies reveal that significant reductions in the optimum curing times are found by using MgO as a co-cure activator. Especially, the rate of vulcanization with conventional 5 phr (per hundred grams) ZnO can be enhanced by more than double, going from 0.3 Nm/min to 0.85 Nm/min by the use of a 3:2 ratio of MgO to ZnO cure activator system that should have high industrial importance. Mechanical and thermal properties investigations suggest that MgO as a co-cure activator used at 60% can provide 7.5% higher M100 (modulus at 100% strain) (0.58 MPa from 0.54 MPa), 20% higher tensile strength (23.7 MPa from 19.5 MPa), 15% higher elongation at break (1455% from 1270%), 68% higher fracture toughness (126 MJ/m
from 75 MJ/m
), and comparable thermal stability than conventionally using 100 % ZnO. Especially, MgO as a co-cure activator could be very useful for improving the fracture toughness in rubber compounds compared to ZnO as a single-site curing activator. The significant improvements in the curing and mechanical properties suggest that MgO and ZnO undergo chemical interactions during vulcanization. Such rubber compounds can be useful in advanced tough and stretchable applications.
This study investigates the human motion sensing capabilities of silicone rubber (SR) composites reinforced with multi-walled carbon nanotubes (MWCNTs). It focuses on assessing the responsiveness of ...the composites to both compressive and tensile deformations, replicating motions from machines to human movements. The analysis underscores the enhanced sensitivity of the 3 parts per hundred (phr) compressive sample, with gauge factors of 7.5 and 14.44 at distinct linear ranges under 30% strain. During forefinger and thumb pressing, the relative change in resistance was 160 and 350, respectively. Additionally, the study examines the 5 phr sample, revealing a significant 346.67% increase in relative resistance changes during the initial cyclic loading phase under 30% tensile deformation compared to the compression sample. The mechanical properties are also evaluated, showing the 5 phr compressive sample possessing a compressive modulus 180.09% higher than the modulus of the unfilled specimen (1.246 MPa), along with a hysteresis loss of 37.24 kJ. Furthermore, the tensile modulus of the 5 phr specimen exceeds that of the unfilled rubber by 218.84%. The developed composites hold promise for creating sensors capable of tracking athletes' movements in real time, offering immediate performance feedback and post-processing analysis. Moreover, these materials could contribute to the design of rehabilitation devices aimed at assisting individuals with hand injuries in regaining their agility and mobility.
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