| 1. |
- Qu, Muchao, et al.
(författare)
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Biocompatible, Flexible Strain Sensor Fabricated with Polydopamine-Coated Nanocomposites of Nitrile Rubber and Carbon Black
- 2020
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 12:37, s. 42140-42152
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Tidskriftsartikel (refereegranskat)abstract
- A flexible, biocompatible, nitrile butadiene rubber (NBR)-based strain sensor with high stretchability, good sensitivity, and excellent repeatability is presented for the first time. Carbon black (CB) particles were embedded into an NBR matrix via a dissolving-coating technique, and the obtained NBR/CB composite was coated with polydopamine (PDA) to preserve the CB layer. The mechanical properties of the NBR films were found to be significantly improved with the addition of CB and PDA, and the produced composite films were noncytotoxic and highly biocompatible. Strain-sensing tests showed that the uncoated CB/NBR films possess a high sensing range (strain of similar to 550%) and good sensitivity (gauge factor of 52.2), whereas the PDA/NBR/CB films show a somewhat reduced sensing range (strain of similar to 180%) but significantly improved sensitivity (gauge factor of 346). The hysteresis curves obtained from cyclic strain-sensing tests demonstrate the prominent robustness of the sensor material. Three novel equations were developed to accurately describe the uniaxial and cyclic strain-sensing behavior observed for the investigated strain sensors. Gloves and knee/elbow covers were produced from the films, revealing that the signals generated by different finger, elbow, and knee movements are easily distinguishable, thus confirming that the PDA/NBR/CB composite films can be used in a wide range of wearable strain sensor applications.
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| 2. |
- Qu, Muchao, et al.
(författare)
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Electric Resistance of Elastic Strain Sensors-Fundamental Mechanisms and Experimental Validation
- 2023
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Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 13:12
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Tidskriftsartikel (refereegranskat)abstract
- Elastic strain sensor nanocomposites are emerging materials of high scientific and commercial interest. This study analyzes the major factors influencing the electrical behavior of elastic strain sensor nanocomposites. The sensor mechanisms were described for nanocomposites with conductive nanofillers, either dispersed inside the polymer matrix or coated onto the polymer surface. The purely geometrical contributions to the change in resistance were also assessed. The theoretical predictions indicated that maximum Gauge values are achieved for mixture composites with filler fractions slightly above the electrical percolation threshold, especially for nanocomposites with a very rapid conductivity increase around the threshold. PDMS/CB and PDMS/CNT mixture nanocomposites with 0-5.5 vol.% fillers were therefore manufactured and analyzed with resistivity measurements. In agreement with the predictions, the PDMS/CB with 2.0 vol.% CB gave very high Gauge values of around 20,000. The findings in this study will thus facilitate the development of highly optimized conductive polymer composites for strain sensor applications.
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| 3. |
- Qu, Muchao, et al.
(författare)
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Electrical conductivity of anisotropic PMMA composite filaments with aligned carbon fibers - predicting the influence of measurement direction
- 2020
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Ingår i: RSC Advances. - : ROYAL SOC CHEMISTRY. - 2046-2069. ; 10:7, s. 4156-4165
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Tidskriftsartikel (refereegranskat)abstract
- In order to study the electrical conductivity of anisotropic PMMA/carbon fiber (CF) composites, cylindrical PMMA/CF filaments were extruded through a capillary rheometer, resulting in an induced CF orientation along the extrusion direction. The aspect ratios of the CFs in the filaments were accurately regulated using a two-step melt mixing process. By measuring the vertical and horizontal resistances of filaments where the outermost layer was successively peeled off, the anisotropic conductivities could be calculated. This was done using a novel analytical model where each cylindrical composite filament was defined as a structure consisting of three concentric cylinders with potentially different conductivities and CF orientations. The electrical conductivity increased with the degree of fiber orientation along the voltage direction and the effects of anisotropy and measurement direction were incorporated into the (isotropic) McLachlan equation. The required distance for electrical contact between the CFs was calculated to be 16 nm. Finite element (FEM) simulations were successfully utilized to confirm the data.
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| 4. |
- Qu, Muchao, et al.
(författare)
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Mechanical and electrical properties of carbon nanotube/epoxy/glass-fiber composites intended for nondestructive testing
- 2023
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Ingår i: Polymers for Advanced Technologies. - : Wiley. - 1042-7147 .- 1099-1581. ; 34:8, s. 2554-2563
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Tidskriftsartikel (refereegranskat)abstract
- In this study, ternary polymer composites sheets comprising glass fiber (GF) reinforced epoxy with various fractions of carbon nanotubes (CNT) were manufactured using hot-pressing technology. A multiscale morphology analysis was presented using scanning electron microscopy. The thermal behavior of the glass fiber reinforced polymer (GFRP) was investigated using thermogravimetric analysis, DSC, and DMA, which indicated an application temperature up to 71°C for the composites. Mechanical uniaxial stretching and three-points bending tests showed that the addition of 0.1–0.2 wt% CNT decreased the dissipated energy of the specimen by 50% and increased the Young's modulus by more than 100%. During all stretching and bending measurements, the relative change in electrical resistance (RCR) was recorded as function of strain, revealing a relationship between the electrical signal and the applied deformation of the GFRP. Finally, the standard equation for fitting RCR versus strain was optimized, reducing the number of fitting parameters from five to three. The electrical and mechanical properties of the CNT/GF/epoxy composites show that they are suitable sensoring materials for wind-turbine blades and other glass-fiber reinforced epoxy constructions, especially for nondestructive testing.
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| 5. |
- Qu, Muchao, et al.
(författare)
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Novel definition of the synergistic effect between carbon nanotubes and carbon black for electrical conductivity
- 2019
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Ingår i: Nanotechnology. - : Institute of Physics (IOP). - 0957-4484 .- 1361-6528. ; 30:24
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Tidskriftsartikel (refereegranskat)abstract
- Anisotropic ternary composites comprising poly(methy-methacrylate) (PMMA), carbon black (CB), and carbon nanotubes (CNTs) were extruded using a capillary rheometer and the electrical conductivities of the composites were measured and presented in a detailed contour plot covering a large range of filler fractions (up to 30 vol% CNTs, 20 vol% CB). A recent generic conductivity model for ternary composites was successfully validated using the conductivity measurements. When analyzing the conductivity measurements using four traditional definitions of 'synergy' between two conductive fillers, no clear synergetic effect was observed between CB and CNT. Also, when all the conductivity data for ternary CNT/CB composites from the existing literature was carefully gathered and analyzed, the number of confirmed occurrences of strong and convincing CNT/CB synergies was surprisingly low. Finally, a novel definition of synergy based on the physical aspect, in particular, its maximum, the 'synergasm', was defined in order to obtain a more precise instrument for revealing regions of potential synergy.
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| 6. |
- Qu, Muchao, et al.
(författare)
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Strain sensing, electromagnetic interference shielding, and antimicrobial performance of triple hierarchic fabric coated with AgNWs and polydopamine
- 2024
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 243
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Tidskriftsartikel (refereegranskat)abstract
- For wearable smart textile sensors, stability, accuracy and multi-functionality are key objectives. Achieving the optimal application requires delicately balancing the crucial physical properties of strain sensors, presenting a key technological challenge. This study addresses these challenges by presenting several properties and potential applications of a triple hierarchic polymeric knitted fabric. The fabric incorporates an internal conductive network constructed with silver nanowires (AgNWs) and polydopamine (PDA) coating on its outer surface. This innovative textile successfully strikes a balance between strain sensing and electromagnetic interference shielding while concurrently exhibiting biocompatibility and antimicrobial properties. Significantly, acknowledging the susceptibility of measurements from polymer-based strain sensor materials to time drift, we introduce both a modeling approach and a novel calibration technique. This advancement facilitates the generation of stable cyclic sensing signals, even under substantial deformations of up to 80 % at a high stretching speed. Importantly, it provides a practical solution for addressing signal drift observed in flexible sensors when utilized in environments characterized by long-term and large deformations.
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| 7. |
- Yang, Guanda, et al.
(författare)
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Novel Theoretical Self-Consistent Mean-Field Approach to Describe the Conductivity of Carbon Fiber-Filled Thermoplastics : PART II. Validation by Computer Simulation
- 2018
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Ingår i: Macromolecular Theory and Simulations. - : Wiley-VCH Verlagsgesellschaft. - 1022-1344 .- 1521-3919. ; 27:4
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Tidskriftsartikel (refereegranskat)abstract
- The electrical conductivity of polymeric fiber composites is generally strongly dependent on the constituent conductivities, the fiber filler fraction, the fiber aspect ratio, and on the orientation of the fibers. Even though electrically conductive polymer composites are emerging materials of high scientific and commercial interest, accurate mathematical models for describing such materials are rare. A very promising mathematical model for predicting the electrical conductivity below the electrical percolation threshold, for both isotropic and anisotropic composites, is however recently published by Schubert. The shortcomings of that study are that the model includes so far only one predicted parameter and that it is not sufficiently validated. In the current study, finite element modeling is used to successfully validate the model of Schubert for isotropic fiber composites and to accurately determine the predicted parameter. These theoretical predictions are finally compared with experimental conductivity data for isotropic carbon fiber/poly(methyl methacrylate) (PMMA) composites with fiber filler fractions in the range 0-12 vol% and fiber aspect ratios from 5 to 30. The model forecasts, without any adjustable parameters, are satisfactory close to the experimental data.
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