Multi-walled Carbon Nanotube Composites Research Articles

(Digital Presentation) Evaluating the Performance of Multi-Walled Carbon Nanotube Composite Microporous Layers Deposited on Carbon Felt Gas Diffusion Layers

Electrochemical energy storage devices (EESDs) such as metal-air batteries (MABs) and alkaline electrolyte membrane fuel cells (AEMFCs) have begun to gain vast amounts of attention due to their high theoretical energy densities and open-circuit voltage values. Although these devices present promising aspects for the environment and sustainability, they suffer from the slow reaction kinetics and degradation effects that occur at the catalyst layer interface of the air electrode. Typically, these effects are due to the accumulation of molecular species such as water or oxygen at catalyst active sites because of poor electrode hydrophobicity and fluid management. Herein, we perform experimentation to mitigate these effects by implementing mixed carbon composite microporous layers onto porous carbon felt based air electrodes. This adaptation of the air cathode was predominantly based on the aforementioned downfalls and the lack of availability of commercial carbon felts that have adequate wet proofing and conductivity like some of the related carbon paper gas diffusion layers. Microporous layers (MPLs) enhance electrical conductivity, surface area, and adhesion at the catalyst layer and gas diffusion layer interface. These layers typically consist of a hydrophobic polymer such as polytetrafluoroethylene (PTFE) and a conductive carbon black substrate such as Ketjen Black 600JD (KJB). The incorporation of multi-walled carbon nanotube (MWCNT) and carbon black composites into the structure of the MPLs drastically decreases ohmic polarization with minimal increases in specific resistance. The electrical resistance of the synthesized carbon substrate decreases at high rates of MWCNT dispersion, which corresponds directly to a low MWCNT weight percentage within the composite. The MPL increases the mass transport through the electrode by mitigating flooding effects that typically occur within the pores near the surface of the catalyst layer, ultimately aiding in charge transfer between the gas diffusion layer and catalyst active sites. Preliminary data from AEMFC symmetric cell tests suggests that a microporous layer consisting of a 10 wt.% MWCNT/KJB (m/m) substrate is the optimal loading of carbon nanotubes and leads to better cell performance. There is an increase in current density of 60 mA/cm2 compared to an air electrode with no MPL within the ohmic region of the polarization curve corresponding to approximately 0.7 V, while only an increase of 18 mA/cm2 is seen for an MPL consisting of a 30 wt.% MWCNT/KJB (m/m) carbon substrate. The increase of charge transfer by the 10 wt.% synthesized carbon substrate MPL was attributed to the ability of the nanotubes at high rates of dispersion to act as molecular wires within the electrode. Additionally, zinc-air battery tests using the optimally configured air electrode, determined from previous experiments, show that the current density at an operating voltage of 1.1 V was increased by 2.3 times that of an electrode without an MPL using the same catalyst material and loading. Significantly, this research will lead to a better understanding of optimization of the air electrode used within electrochemical devices and how to eliminate some of the adverse effects associated with it. Figure 1

Highly conducting PANI- fMWNT composites with exceptional crystallinity and enhanced thermal stability for potential applications

Here we report, the synthesis and characterization of the thin film of polyaniline-functionalized multiwalled carbon nanotube composite with exceptional electrical conductivity, excellent crystallinity and improved thermal stability. In this study, the multiwalled carbon nanotubes were functionalized using formaldehyde through an electrophilic substitution reaction and methylol groups (-CH2OH) attached to the sidewalls of the nanotubes. A significant dispersivity of polyaniline-multiwalled carbon nanotube composites was achieved as a result of the functionalization. The thin film of polyaniline-functionalized multiwalled carbon nanotube composite was prepared via the doping-dedoping-redoping process. The structural, morphological, thermal and conductivity studies of the synthesized polyaniline-functionalized multiwalled carbon nanotube composite samples were carried out using various characterization tools. The thin film sample shows an enhanced electrical conductivity of 1991 S/cm, which is pretty high among the reported values for polyaniline-carbon nanotube composites. It also exhibits an excellent crystallinity of 84.44%, the highest value ever reported. The thermal stability of the thin film sample is very high compared to the polyaniline sample. The charge transfer mechanism in the synthesized samples was investigated using the three-dimensional variable range hopping model. The ANOVA and regression analysis was performed to assess the validity of the model.

Efficient enrichment of pesticides from environmental water samples by cobalt-nickel double metal hydroxide nanocage/multiwalled carbon nanotube composites

建立高效、灵敏的农药分离、富集和检测方法具有重要意义。该实验采用一步法合成了钴基沸石咪唑骨架/多壁碳纳米管(ZIF-67/MWCNTs)复合物,并以该复合物为模板通过溶剂热法合成了钴镍笼状双金属氢氧化物/多壁碳纳米管(CoNi-LDH/MWCNTs)复合材料,将CoNi-LDH/MWCNTs用作固相微萃取(SPME)的纤维涂层富集环境水样中的6种农药,结合高效液相色谱(HPLC)测定了环境水样中的6种农药。通过扫描电镜、能谱分析、红外光谱、粉末X射线衍射和N2吸附/脱附对所制备的各种材料进行了表征。利用正交设计试验优化SPME的萃取条件,包括萃取温度、萃取时间、搅拌速率、解吸时间和盐浓度。在最优化的条件下,该方法具有较宽的线性范围(百菌清为0.015~200 μg/L,戊唑醇为0.140~200 μg/L,毒死蜱为0.250~200 μg/L,仲丁灵为0.077~200 μg/L,溴氰菊酯为1.445~200 μg/L,哒螨灵为0.964~200 μg/L)、较低的检出限(0.004~0.434 μg/L)和良好的重复性。单个纤维和不同批次纤维间的相对标准偏差(RSD)分别为0.5%~5.7%和0.5%~4.8%。在10.0 μg/L和50.0 μg/L 2个水平下的加标回收率为83.9%~108.2%, RSD< 5.3%。此外,与其他涂层纤维相比,CoNi-LDH/MWCNTs涂层对农药具有更高效的富集能力,这归因于它的高比表面积以及CoNi-LDH/MWCNTs涂层与目标分析物之间存在的π-π堆积作用、疏水作用、阳离子-π相互作用和氢键作用。该方法可以实现环境水样中农药残留的高选择性、高灵敏度及高准确性的分析测定。

Enhanced anti-biofilm and biocompatibility of Zn and Mg substituted β-tricalcium phosphate/functionalized multiwalled carbon nanotube composites towards A. baumannii and Methicillin-Resistant Staphylococcus aureus, and MG-63 cells

In this work, Zn and Mg substituted β-tricalcium phosphate/functionalized multiwalled carbon nanotube (f-MWCNT) nanocomposites were prepared by the co-precipitation method. The structural, vibrational, morphological and biological properties of the prepared nanocomposites were studied. The structural study revealed that the increase of Zn concentration shifts the β-tricalcium phosphate planes towards higher angle. Morphological analysis confirmed the formation of hexagonal-shaped particles after substitution of Zn. The particle size of the nanoparticles decreased with the increase of Zn concentration. XPS analysis clearly showed the presence of Zn, Mg, P, Ca, O and C. The Zn (5%) rich nanocomposites have better antibiofilm activity compared to 2% of zinc substituted composite. Also, it has been proven that the prepared nanocomposites have the ability to enhance the bioactivity of commercial antibiotics by means of a decrease in drug resistance. Finally, this study acted as a pioneer to improve drug efficiency and reduced the biofilm formation of certain medically important bacteria. The in-vitro cell viability and anti-biofilm results of zinc (5%) rich nanocomposite confirmed that prepared nanocomposite has biocompatible and enhanced anti-biofilm property, which will be beneficial candidate for biomedical applications.

Development of multi-walled carbon nanotube/polythiophene (MWCNT/PTh) nanocomposites for platinum-free dye-sensitized solar cells (DSSCs)

Platinum is utilized to a significant degree as a catalyst material in the fabrication of dye-sensitized solar cells. However, its utilization is constrained by its high cost, scarcity, requirement for high purity, poor corrosion resistance against liquid electrolytes, and energy-intensive deposition techniques. It is possible to substitute platinum with carbon allotropes or composites built of conductive polymer materials. In this study, in-situ polymerization was used to synthesize nanocomposites of multi-walled carbon nanotubes and polythiophene. X-ray Diffraction, Fourier-Transform Infrared Spectroscopy, and Scanning Electron Microscopy were used to examine the interactions between ingredients and the morphological features of composites, respectively. The results showed that the amount of multi-walled carbon nanotubes in composites affects the effectiveness of solar devices. Compared to cells based on 10% and 60 %MWCNTs/PTh, the efficiency of the cell that was made with 30 %MWCNTs/PTh exhibited a greater level of performance. The results also showed that the MWCNTs/PTh device outperformed Pt-based solar cells in terms of performance.

The effect of multi-walled carbon nanotubes on the thermo-physical properties of shape stabilised phase change materials for buildings based on high density polyethylene and paraffin wax

The inherent low thermal conductivity and inferior mechanical properties of polymer based shape stabilised phase change materials (SSPCMs) restrict their wide applications in building sections. Multi-walled carbon nanotubes (MWCNTs) with excellent thermal and mechanical properties were incorporated into SSPCMs based on blends of a low molecular weight HDPE (lv-HDPE) and paraffin waxes by extrusion. Their suitability for latent heat thermal energy storage was evaluated. The MWCNTs were uniformly distributed within the SSPCM matrix and were wetted by the SSPCM. The SSPCMs with MWCNTs had latent heats up to 53 J g−1 with 0.5 wt% MWCNTs. Both the Young's moduli and yield stress of lv-HDPE50H-PW50 with MWCNTs composites were lower than that of unfilled lv-HDPE50H-PW50 at low MWCNT loading (≤1 wt%). They then went up with an increase in MWCNT loading (from 1 wt% to 3 wt%). This is due to the formation of an inter-connected network of MWCNTs. Similar results were obtained for both flexural moduli and stress. However, there is no significant difference of the compression moduli between unfilled lv-HDPE50H-PW50 blend and those MWCNT blends. The thermal conductivity increased with increasing MWCNTs content and the greatest enhancement was 29 % for SSPCM with 3 wt% MWCNTs. It will therefore contribute to the decarbonisation of buildings.

Electrical and Mechanical Properties of Polymer Composite through the Use of Single-Walled Carbon Nanotube and Multi-Walled Carbon Nanotube

To manufacture composites with required properties, it is extremely important to select an appropriate filler. Carbon-based nano materials such as carbon black, graphene and carbon nanotube (CNT) have been extensively investigated as reinforcing and conducting fillers. Because of their high aspect ratio coupled with superior physical properties, 1-dimensional CNTs are ideal as filler materials to impart electrical conductivity to insulating polymers, while enhancing mechanical strength. In this study, we investigated the piezo-resistive and mechanical properties of composites consisting of two types of CNT classified as multi-walled CNT (MWNT) or single-walled CNT (SWNT) depending on the number of walls. Since MWNT and SWNT have different physical properties such as specific surface area and aspect ratio, this can affect the composite’s performance. To more effectively evaluate the effect of MWNTs and SWNTs in composites, we used thermoplastic polyurethane (TPU) as a matrix, which is an insulating stretchable elastomer. Morphological and mechanical/electrical characterizations were conducted to determine differences in the MWNT and SWNT composites. In addition, we conducted dynamic strain sensing tests on each type of CNT composites to compare the sensitivity as a strain sensor. Differences in piezo-resistive behaviors were attributed to the loss of electrical contact points during stretching. These results can serve as a useful design guideline for the wider use of CNT composites.

Solvent-induced crack growth in poly(methyl methacrylate)/multiwalled carbon nanotube composites

Understanding the structural integrity of polymer composites in service conditions is of practical importance for the applications of polymer composites. In this work, we investigate the solvent-induced crack growth in poly(methyl methacrylate)/multiwalled carbon nanotube (PMMA/MWCNT) composites in respective organic solvents of 2-ethylhexyl alcohol (2 EA), cyclohexanol, and 1-butanol at different temperatures after being immersed in methanol at 50 °C for 25 min. The areal density of crack lengths and growth rate of a single crack in the PMMA/MWCNT composites increase with the immersion time and temperature for the solvents of 2 EA and cyclohexanol. The areal density of crack lengths in the PMMA/MWCNT composites immersed in 1-butanol is largest at 30 and 40 °C and smallest at 50 °C. The 1-butanol solvent causes the fastest, steady-state crack growth at 30 and 40 °C and the slowest crack growth at 50 °C. Increasing the fraction of MWCNTs reduces the areal density of crack lengths and the growth rate of a single crack in the healed and non-cracked areas. The crack growth is controlled by a thermally activated process. The crack growth rate is faster in the healed area than in the non-cracked area for the same composite and solvent. The activation energy for the motion of polymer chains associated with the single-crack growth in the non-cracked area is smaller than that for solvent-induced cracking because the interaction between cracks hinders crack growth.

Screen printing of graphene-based nanocomposite inks for flexible organic integrated circuits

Graphene and multiwalled carbon nanotube (CNT) composites have been reported to be suitable conductive inks for screen-printing technology, which is a viable option for electrode patterning in organic integrated circuits. Considering the physical properties of the graphene–CNT composite ink, the optimized screen-printing conditions produce graphene–CNT patterns with good pattern fidelity. In addition, the use of a centrifugal mixer enables the composite to disperse graphene and CNT molecules well, stabilizing electrical conductance. In this study, these screen-printed graphene–CNT electrodes were applied to fabricate organic field-effect transistors (OFETs) on a glass substrate. The p- and n-type devices performed satisfactorily. Furthermore, screen printing of graphene–CNT enabled the integration of OFETs for fabricating complementary inverters, NAND, and NOR gates. We believe that the characterization of graphene–CNT inks can promote the advancement of organic integrated circuits beyond unit OFET devices based on an easy-to-use screen-printing technique. • Graphene/CNT composite ink was developed for screen-printing technique. • Using a centrifugal mixer produced well-distributed graphene/CNT patterns with high fidelity. • Integrated circuits with screen-printed graphene/CNT showed robust operation.

Copper Phthalocyanine MWCNTs Composites: Characterization and Evaluation for Sensor and Solar Cells interlayer

Copper Phthalocyanine (CuPc) thin film with and without multi-walled carbon nanotubes (MWCNTs) is prepared using the solution based method and used in gas sensor and solar cell applications. The structural characteristics of the CuPc thin films showed a single peak around 7o with the preferred orientation for charge transportation. Using atomic force microscopy (AFM), morphological properties show a rough surface with some aggregates and ribbons. The optical absorption properties were determined using UV-Visible absorption spectroscopy; the optical band gap has varied after adding MWCNTs to CuPc. Electrical conductivity of CuPc:MWCNTs composite is higher than that of the pure CuPc. The CuPc thin film sensr have shown good response properties to ammonia gas. The solar cell performance of the P3HT:PCBM based solar cell was enhanced.

Multi-walled carbon nanotubes wrapped with polyvinylpyrrolidone can control the leaf yellowing of Alstroemeria cut flowers

The rapid yellowing of the leaves on cut flowers with leafy stems severely limits their vase life and commercial value. In this study, the effect of a composite of multi-walled carbon nanotubes (MWCNTs) and polyvinyl pyrrolidone (PVP) on the longevity of cut Alstroemeria flowers (Alstroemeria hybrida) was investigated to obtain a solution to this problem. A range of MWCNTs/PVP composite concentrations (0, 3, 6, and 9 mg L−1) was applied in a vase solution (for 24 h) as pulse treatments. Our findings indicate that the composite of MWCNTs and PVP exhibits excellent dispersibility in a vase solution. The results demonstrate that a 3 mg L−1 MWCNTs/PVP concentration was the most effective, extending the vase life of cut Alstroemeria flowers by up to 27 days. Pulsing with MWCNTs/PVP delayed the onset of floret abscission and leaf yellowing by 5 and 18 days, respectively. Additionally, when MWCNTs/PVP solution was applied to cut stems, water uptake remained consistently greater than that of the control. Additionally, MWCNTs/PVP increased the total chlorophyll content, soluble protein content, and POX enzyme activity of leaves while decreasing the malondialdehyde (MDA) content. The results indicate that this composite exhibited antimicrobial activity against gram-positive and -negative bacteria, particularly at a concentration of 3 mg L−1. This study demonstrated that adding MWCNTs/PVP to a vase solution of Alstroemeria cut flowers increased their longevity with minimal leaf yellowing symptoms compared to untreated cut stems. As a result, this nanocomposite can be used safely and effectively in vase solutions and in combination with other preservatives.

Preparation of fluororubber/carbon nanotube composites and the effect of carbon nanotubes on aging resistance and solvent resistance of fluororubber

Improvement of the aging resistance of the rubber composites for oil and gas exploitation has been attracting the interest of scientists. In this work, the Fluororubber (FKM)/multi-walled carbon nanotube (MWCNTs) composites were prepared to prolong the service life of sealing materials for packers, and the effect of MWCNTs on the vulcanization parameters, mechanical properties, aging resistance and medium resistance of FKM were studied, respectively. The results showed that with an increase of MWCNTs in content, both the maximum torque (MH) and the positive curing time (t90) gradually increased. The tensile strength and hardness of the FKM composites exhibited the trend of increase, and decrease tendence in elongation at break; The FKM composites showed good aging resistance at 177 °C, 204 °C and 232 °C for 192 h in a dilute oxygen environment. After immersed in mediums for 20% H2SO4, 28% NH3·H2O and acid mixture solution with 1 of pH value for 192 h, the mechanical properties decreased slightly over the experiment period. The high temperature aging resistance and corrosion resistance of FKM composites in mediums did not show a positive relationship with the MWCNTs content. The appropriate addition of MWCNTs exhibited better enhancement effect.

Fabrication of highly electrically conductive polypropylene/polyolefin elastomer/multiwalled carbon nanotubes composites via constructing ordered conductive network assisted by die‐drawing process

AbstractIn this work, a facile strategy is proposed to prepare highly electrically conductive polypropylene (PP)/polyolefin elastomer (POE)/multiwalled carbon nanotubes (MWCNTs) composites with ordered conductive networks using a house‐made die‐drawing apparatus. Results showed that increasing either die‐drawing speed or drawing ratio led to an increase of crystallinity by 10% and orientation factor by 0.15 for PP, respectively, which played an important role in tuning the electrical conductivity and mechanical properties. Prior to die‐drawing process, MWCNTs were selectively distributed in POE domains, resulting in a remarkable increase of electrical conductivity. The prevailing high‐stress field during die‐drawing process was able to deform MWCNTs‐enriched POE domains to ordered microfibrillar structure, as confirmed by morphology observations. This resulted in a further increase of electrical conductivity for die‐drawn PP/POE/MWCNTs composites when compared with that of MWCNTs‐containing counterparts without die‐drawing. Moreover, both the tensile strength and elongation at break for die‐drawn PPCNTE30 composites were increased by 20% and 127% as compared with their counterparts without die‐drawing treatment.

Polybenzoxazine/carbon nanotube nanocomposites as a polymeric sensing material for volatile organic compounds

The emissions of volatile organic compounds (VOCs) have hazardous effects on humans and the environment, and hence they should be detected and reduced. In this study, polybenzoxazine (PBZ) and amine-functionalized multiwall carbon nanotube (MWCNT) composites were synthesized as a sensor for VOCs. MWCNT were functionalized with two types of diamines, namely, 1,6-hexanediamine (HDA) and phenylenediamine (PDA). HDA or PDA treated MWCNTs were loaded into the benzoxazine matrix with different weight percentages (0.1, 0.3, 0.5, and 1%). FTIR analysis confirmed the chemical attachment of the two types of diamines on MWCNT. XRD diffraction and scanning electron microscopy (SEM) were used to investigate the nanofillers morphology and clarify the differences between pristine and amine-functionalized MWCNT. Thermal gravimetric analysis (TGA) was used to study the composites’ thermal stability and degradation behavior. It was found that, in contrast to neat PBZ, the major degradation temperature of PBZ/0.5%MWCNT-PDA nanocomposites were enhanced by 10%. The electrical conductivity of PBZ was 6.32 × 10–9, which was enhanced to 6.11 × 10–7 in the composites with 1% MWCNT-PDA. This material was tested as a VOCs sensor for methanol, acetone, and toluene and showed that PBZ/1% MWCNT-PDA composite responded to all the vapors.

Magnetic field driven dielectric relaxation in non-magnetic composite medium: A low temperature study

The frequency dependence of dielectric constant for composites of polyaniline (PANI) and multi-walled carbon nanotube (MWCNT) with different degree of functionalization is studied at low temperature (down to 4.2 K) and magnetic field (up to 3 T) applied both in parallel and perpendicular direction of ac electric field. A relaxation phenomenon is observed in all the MWCNT/PANI composites by applying magnetic field in both the directions, below 103 Hz. However, PANI does not show any relaxation peak with applied magnetic field in either direction. The relaxation peak frequency does not depend on the strength of magnetic field but it varies with temperature and degree of functionalization of MWCNT in composites. This relaxation phenomenon occurs due to the inhomogeneity of the medium of two highly mismatched conductive materials at low temperatures. The results are explained in the light of Parish and Littlewood theory about magnetocapacitance in nonmagnetic composite.

Amorphous and Crystalline Vanadium Orthophosphate and Oxidized Multiwalled Carbon Nanotube Composites as Anode Materials in Sodium‐Ion Batteries

AbstractInvited for this issue's Front Cover is the group of Prof. Krzysztof Winkler from the Department of Chemistry, University of Bialystok (Poland). The cover picture schematically illustrates the electrode process that runs during reduction of a composite consisting of the vanadium phosphate and multiwalled carbon nanotubes for a sodium‐ion battery. Such material exhibits promising capacitance properties, good rate performance and long lifetime. It can be used as anode material in sodium‐ion batteries. Read the full text of the Research Article at 10.1002/celc.202200174.

Front Cover: Amorphous and Crystalline Vanadium Orthophosphate and Oxidized Multiwalled Carbon Nanotube Composites as Anode Materials in Sodium‐Ion Batteries (ChemElectroChem 16/2022)

Front Cover: Amorphous and Crystalline Vanadium Orthophosphate and Oxidized Multiwalled Carbon Nanotube Composites as Anode Materials in Sodium‐Ion Batteries (ChemElectroChem 16/2022)

Facile synthesis of hierarchical Co3O4/MWCNT composites with enhanced acetone sensing property

A facile hydrothermal approach is reported for the preparation of a series of hierarchical cobalt tetraoxide (Co3O4)/multi-walled carbon nanotube (MWCNT) composites with different MWCNT amount. The material characterization reveals that the broccoli-like nano-agglomerates of Co3O4 nanoparticles are anchored to the surface of the intertwined MWCNT network structure in all the Co3O4/MWCNT composites. The optimized Co3O4/MWCNT based chemiresistive sensor has ultralow limit of detection of 0.41 ppm, and up to 5 times greater sensing response than the pristine Co3O4 based sensor while exposed to 100 ppm of acetone gas at 140 °C. The Co3O4/MWCNT based sensor has a short response time of 15 s and a short recovery time of 18 s, respectively. In addition, the Co3O4/MWCNT based sensor presents long-term stability, good reproducibility and high selectivity. The possible mechanisms of the enhanced chemiresistive response of the composite include the formation of the p-p hetero-junctions at the interface between Co3O4 and MWCNT, the increased amount of adsorbed oxygen species on the composite surface, and the mesoporous structure of the composite.

Effect of Carbon Nanotube Content and Mechanical Milling Conditions on the Manufacture of AA7075/MWCNT Composites

Aluminium matrix composites (AlMCs) of AA7075 aluminium alloy reinforced with 0.5 and 1 wt.% multiwall carbon nanotubes (MWCNTs) were fabricated with powder metallurgy techniques using three different mechanical milling strategies, varying the milling energy and the stage in which the reinforcements were added to the pre-alloyed matrix powders. In this paper, we focus on the influence of these parameters on the dispersion of MWCNTs. Characterization of the obtained composite powders by X-ray diffraction and scanning electron microscopy showed that the evolution of the particle size and morphology of the composite powders is influenced by milling conditions and MWCNT content; however, under the conditions tested in this study, there were no significant differences in crystallite size and lattice strain. The best distribution of the reinforcements was obtained after milling 7075 powders and MWCNTs in a high-energy cycle (HEBM), varying the rotation speed between 1200 and 1300 rpm. Raman spectroscopy was used to assess the damage induced by the milling process in the nanotubes, and no reaction products were detected under any of the tested conditions. Nanoindentation tests were performed to measure the elastic modulus and hardness of the composite powders, revealing that the best mechanical behaviour was achieved by the 7075-0.5 wt.% MWCNT composites obtained by the HEBM route.

Application of a Tactile Sensor for the Gait Phase Classification for an Exoskeleton

This paper presents the design and implementation of fuzzy logic control for human walking using lab-developed sensors and the second lower limb robotic exoskeleton (LLRE-II) to detect gait phases. A piezoresistive tactile sensor (PRTS) was developed and used to measure the foot pressure to predict human walking behavior. The proposed sensor with grid structures was then fabricated using polymer composites of multi-walled carbon nanotubes (MWCNTs) combined with polydimethylsiloxane (PDMS). The doping ratio and design of the grid structure of the sensors were optimized to achieve a good sensing range. The foot reactive forces measured by the four sensors were calculated and converted to force ratio factors to improve the performance of gait phase detection by the fuzzy logic control. Based on the sensor tests, the most stable doping ratio was fixed as 7 wt%, and the ratio of the grid structure (line width:line spacing:thickness) was 1:1:1. Sensors were set in the soles of the shoes on the foot pads of the exoskeleton, and the foot reactive forces were captured for analysis. The performance of the proposed algorithm for gait phase detection was verified experimentally. The results indicated that both regular and irregular walking could be detected by the proposed method.