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Abstract

This research focused on understanding the microbe killing mechanism of the antimicrobial properties of highly elastic conductive poly(ethylene terephthalate) (PET)/multi-walled carbon nanotube (MWCNT) powernet fabrics with the help of electric fields and highly elastic structure. In this study, PET/MWCNT fabrics containing three different percentages of MWCNT were knitted and characterized with antimicrobial activity, cytotoxicity, electromagnetic shielding properties, DSC analyses, stiffness tests, and pressure measurements using wireless pressure sensors. Results show that MWCNT has a statistically significant effect on antibacterial activity, cytotoxicity, electromagnetic shielding, stiffness, and exerted pressures. PET/MWCNT fabrics showed excellent antibacterial activity against tested germs; S. aureus and E. coli. A statistically significant increase in percentage reduction of bacteria was observed with the increase in carbon nanotube nanoparticle concentration, accompanied by a good laudering durability even after 20 washing cycle. In terms of cytotoxicity tests, all PET/MWCNT samples were found to have over 70% average relative cell viability, indicating that they are noncytotoxic without interrupting the cell line and primary cell growth in vitro. The materials have provided longer conductive networks and formed electromagnetic shielding at the range of 22.79 dB-25.77 dB at the frequency of 0–1.30 GHz. Moreover, MWCNT concentration did not lead to considerable changes in physical properties like stiffness and exerted pressure properties. Characterization analyses confirmed the changes in the chemical structure of the PET/MWCNT.

Keywords

antimicrobial cytoxicity PET/MWCNT electromagnetic shielding wireless pressure sensors

Introduction

Electrically conductive polymers are candidates for a variety of uses including semiconductor chips, integrated circuits, electrodes, lightweight battery components, sensors, electrochromic displays, and static-free packaging material.^1,2 Several studies have been reported on the incorporation of electrically conductive additives such as carbon nanotubes (CNTs) into fibers or their coating onto fabrics that can both improve mechanical and electrical properties and enable the multi-functionality required for electrical energy storage, sensing and actuation.^3–9 There has been increasing interest in incorporation of CNTs into polymers such as poly(ethylene terephthalate) (PET), polypropylene (PP), polyimide and polyamide for formation of fibers.^10,11 Thermal stability and time stability are important properties for polymer fibers/composites to observe their degradation and behavior versus temperature and time.^12,13 In a study conducted at the Center for Bio-Artificial Muscle and Department of Biomedical Engineering, South Korea, a more alignment and stable structure is achieved when these nanoparticles were added during spinning processes.¹⁴ It was reported that thermal stability of the fibers was not significantly affected by the presence of CNTs at low concentrations (up to 2%).^15,16 However, their biocompatibility also plays a vital role for in vivo use.^17–19

Multi-walled carbon nanotubes (MWCNTs) have attracted special interest for industry and are widely used for a variety of commercial products due to their super mechanical strength, thermal conductivity, high surface area, well-defined morphologies, and unique optical and electrical properties.²⁰ There are also several studies on the antibacterial properties of MWCNTs. In a study on the antibacterial activity of MWCNT, MWCNT samples were treated with an acid mixture of H₂SO₄ and HNO₃ produced oxygen-containing functional groups (e.g. OH, C=O, COOH) with nominal damage to the structure of the nanotubes.^21,22 Kang et al. provided the first evidence that the diameter of carbon nanotubes (CNTs) is a key factor governing their antibacterial effects, and that the possible main CNT cytotoxicity mechanism is cell membrane damage by direct contact with CNT.²³ Olivi et al. reported that individually dispersed nanotubes could be visualized as numerous moving nano darts attacking bacteria in a buffer solution, causing degradation of bacterial cell integrity that led to cell death. This mechanism occurs through adhesion to the surface of microbial cells, interruption of transmembrane electron transfer, disruption/penetration of the cell envelope, DNA damage, and oxidation of cell components.²⁴

In addition, CNTs have shown great potential for use in electromagnetic interference (EMI) shielding materials due to their outstanding electronic properties. Al-Ghamdi found that there is a positive correlation between shielding and electrical conductivity.²⁵ A radio-frequency (RF) electromagnetic field (EMF) comprising the frequency range from 100 kHz to 300 GHz is used in a variety of technologies including mobile telephones, broadcasting and TV, microwave oven, radar, portable and stationary radio transceivers, personal mobile radio, MRI.²⁶ RF EMF affects the human body even at low levels of exposure to electromagnetic fields at home, resulting in headaches, anxiety, suicide and depression, nausea, and fatigue. It can be explained by the electromagnetic theory that electromagnetic energy passing through the body will establish a potential gradient in the human body. From this point of view, the standing waves produced will naturally create heat in the body and raise the body temperature.²⁷

In the current literature on the modification of polyethylene terephthalate (PET) fibers/fabrics with CNTs, researchers have mostly focused on improving electrical properties.^28–34 Mazinani et al. (2010) produced PET/MWCNT conductive fibers at a MWCNT concentration of 2% w/w, and reported that more conductive fibers could be obtained at higher draw rate without increasing the MWCNT concentration.²⁹ The rheological and electrical conductivity of PET/MWCNT nanocomposites were investigated by Hu et al.³³ Sivasubramaian et al. (2012) prepared the composite material of polypyrrole/MWCNT/PET fabric by coating the surface of PET fabric with a combination of polypyrrole (PPy) and MWCNTs. The results show that the fabricated composite materials have improved conductivity and high specific capacitance, making them suitable for use as electrodes in supercapacitors.³⁵ Lin et al. (2016) applied the melt extrusion method to coat the PET yarns with polypropylene (PP) and MWCNTs for producing wires. PP/MWCNTs-coated PET conductive yarns exhibited satisfactory tensile properties and electrical conductivity for use in functional woven and knitted fabrics.³⁶ Arbab et al. (2015) coated polyester fabric with enzyme-dispersed MWCNT suspensions by a simple tape casting method for the development of textile-integrated solar cells.³⁷

In this study, for the first time, highly elastic conductive PET/MWCNT powernet fabrics were produced from MWCNT integrated melt-spun PET yarns to enhance antibacterial activity and electromagnetic shielding effect (EMS) for functional purposes in pressure garments. Another original point of this research is to focus on the understanding of the antimicrobial properties of highly elastic conductive PET/MWCNT powernet fabrics through the microbe killing mechanism with the help of electric fields and highly elastic structure. Therefore, the fabricated fabrics were characterized in terms of antibacterial activity against S. aureus and E. coli and electromagnetic shielding effect (EMS). Pressure garments designed for use in medical applications like low blood pressure, muscle starins and sprains, are worn for long periods of time (24 h/7 days). These highly stretch garments should maintain their elastic recovery during use by motions, activity for rehabilitation purposes. For this purpose, the stiffness and exerted pressures using wireless pressure sensors were also tested. However; toxic impacts of MWCNTs are still poorly understood. Therefore, in this study, in vitro biocompability of MWCNTs was assessed using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay with L929 mouse fibroblast cells. The effects of multi-walled carbon nanotube (MWCNT) nano-particles at three different concentrations on the polyethylene terephthalate (PET) structure were also evaluated. DSC analysis was performed to observe the effect of MWCNT addition on the thermal transition properties of the PET structure.

Experimental

Material

The extrusion grade polyethylene terephthalate (PET) and MWCNT were supplied from Sigma-Aldrich (St Louis, MO, USA). The supplied MWCNT has a purity higher than 95% MWCNT, a length of 5 μm with 6–8 walls with a diameter 5.5 nm prepared by chemical vapor deposition using cobalt and molybdenum as catalysts (CoMoCAT).

Methods

Production of PET/MWCNT powernet fabrics

Bicomponent fiber production (PET/MWCNT) was conducted by pulling of two polymers from the nozzle hole at the same time under the given process conditions in Table 1. MWCNT (masterbatch dosage) percentages were 20 wt%, 25 wt%, and 30 wt%, and labelled as A, B and C, respectively (Table 2). The masterbatch feedings were 13.8 kg/h for A samples (20 wt% of MWCNT), 15.6 kg/h for B samples (25 wt% of MWCNT), and 18.5 kg/h for C samples (30 wt% of MWCNT).

Table 1.

Process conditions of bicomponent fiber production.

Extruder temperature	280^oC
Dryer temperature	160^oC
Spin beam temperature	282^oC
Pack pressure	156 bar
Spin pump speed	12.44 m/min
Finish pump speed	25 m/min
Godet speed 1	3,260 m/min
Godet speed 2	3,255 m/min
Winder speed	3,250 m/min

Table 2.

Technical specifications of the produced MWCNT integrated melt-spun PET yarns and prepared PET/MWCNT powernet fabrics for samples A, B, C.

	MWCNT percentage (%)	Linear density of the yarns (dtex)	Fabric weight (g/m²)	Thickness of the fabric (mm)	Course yarn density (course/cm)	Wales yarn density (wales/cm)
Sample A	20	167.8	246.5	0.601	14	16
Sample B	25	168.7	246.8	0.602	14	16
Sample C	30	167.9	246.5	0.601	14	16

Melt spun MWCNT integrated polyester yarns were knitted using 30% elastane yarns, which have a great function for rehabilitation, in the powernet warp knitting structure due to their elastic structure and elastic recovery properties. Powernet warp knitting structure is a knitting structure produced on a raschel machine with inlaid yarns, in which each needle in the knitting width is fed by at least one yarn and in line with the direction of fabric production. The elastane yarn number was 47 tex. Table 2 shows the technical properties of the produced MWCNT integrated melt-spun PET yarns and prepared PET/MWCNT powernet fabrics, for samples A, B, C.

The cross-section of the PET/MWCNT fabric structure and the yarn cross-section were taken by an optical microscope. The powernet warp knit stitch diagram, the microstructure of the carbon atoms arrangement taken by an optical microscope and the homogenity of the crosslinking of MWCNT with PET can be clearly seen in Figure 1.

Figure 1.

(a) The cross-section image of 20 wt.% PET/MWCNT sample (b) Powernet warp knit stitch diagram.

Antibacterial activity

The experimental method used to determine the antibacterial effects was AATCC Test Method 100: 2004 “Assessment of Antibacterial Finishes on Textiles” Standards, using Staphylococcus Aureus (S. aureus) ATCC 6538 and Escherichia Coli (E. coli) ATCC 25922 (2.00 × 10⁵ CFU/mL) test inoculum. The AATCC Test Method 61 (2A): 2010 “Colorfastness to Laundering: Accelerated” was followed to evaluate the washing durability. The samples were evaluated after 10 and 20 washing cycles. The percentage reduction of bacteria was calculated according to the related equation (1) given in the Supporting Information.

Cytotoxicity testing: cell viability

The average relative cell viability was determined to evaluate the toxicity of PET/MWCNT material by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay with L929 mouse fibroblast cells. Firstly, cells were cultured in MEM-Alpha medium supplemented with 10% fetal bovine serum (FBS). They were then incubated at 37^°C in a wet atmosphere containing 5% CO₂. The tested PET/MWCNT fabrics were cut into 2.5 cm × 2.5 cm pieces and soaked in a 2 mL culture medium with no FBS for 3 days. The extracts were diluted to a concentration of 25% with a culture medium and then L929 cells were seeded in 96-well plates at a density of 2000 cells per well and incubated for 24 h. Subsequently, the medium was removed and replaced by prepared extracted dilutions. After incubation for 24, 48 and 72 h, the cells were treated with 20 μL per well MTT solution (5 mg mL⁻¹ in phosphate-buffered saline, PBS) and incubated for another 4 h at 37^oC. After that, 200 mL per well dimethyl sulfoxide (DMSO) was added to dissolve the formazan crystals.³⁸ The plates were shaken for 15 min, and the optical density was detected on a multiwell microplate reader (Tecan GENios, Tecan Austria GmbH, Salzburg, Austria) at 490 nm. Cell viability was calculated according to the related equation (2) given in the Supporting Information.

Electromagnetic shielding effect

The electromagnetic shielding properties were evaluated according to ASTM 4935; a standard test method for measuring the electromagnetic shielding effectiveness of planar materials. This test method provides a procedure for measuring the electromagnetic (EM) shielding effectiveness of a planar material due to a plane-wave, far-field EM wave. From the measured data, near-field SE values may be calculated for magnetic (H) sources for electrically thin specimens. The measurement method is valid over a frequency range of 30 MHz to 1.5 GHz. The near-field shielding effectiveness (SE) is the ratio of power received with and without a material present for the same incident power. Shielding effectiveness was calculated according to the related equation (3) given in the Supporting Information.

The measurements were taken from different parts of the samples between 30 MHz–1.5 GHz frequencies and repeated 10 times. The shielding effect data were all obtained in the unit of dB. Then, the obtained results were evaluated according to FTTS-FA-003 (2005) (Functional Technical Textile Standard) as given in the Supporting information. Functional Technical Textile Standard was used to determine the required shielding effect (SE) for the significant shielding effect values.

Differential scanning calorimetry

DSC analysis was used to measure enthalpy changes as a function of temperature/time with the addition of MWCNT. Thermal transitions of the samples were determined using the Perkin Elmer Diamond 7 DSC device. In the DSC procedure, a small sample (5–10 mg) in weight was pressed into an aluminum mold and the heating-cooling-heating cycles were applied at 30°C–300°C. After the first heating cycle, the sample was kept at 300^oC for 2 min before being cooled to 0°C. The first heating was carried out at 10°C/min with successful cooling and heating cycles of 10°C/min and the analysis was repeated three times.

Stiffness tests (bending rigidity)

The produced highly elastic structures need fitting on the body to provide needed exerted pressures to achieve their functions. Therefore, the elasticity of the fabrics should be protected. Stiffness (bending rigidity), one of the most widely used parameters to judge bending rigidity and fabric handling, was tested to evaluate the change in elasticity of the samples with the addition of MWCNT. Stiffness was measured for all samples according to ASTM D5732, 2001. The samples were conditioned for 24 h at 20^oC, with 65% relative humidity before testing.

Pressure measurements

The constant stretching and re-stretching of the fabric will eventually wear down the elasticity of the pressure garment and cause it to lose its ability to exert the correct pressure. So, the pressure measurements were performed to see the effects of all samples for newly designed pressure garments. Exerted pressure measurements were taken on each garment designed for calf and ankle (from ankle to knee), the most active parts of the body, using a static mannequin. They were tested using wireless pressure sensors with 10 repeats after samples were conditioned for 24 h at 20^oC, 65% relative humidity. Measurements were recorded using calibrated pressure sensors that were connected to a data acquisition and management software program by wireless transmitters.

Statistical analysis

The statistical analysis of the experimental data was performed using the JMP version 8.0.2 software package (SAS Institute, Inc. Cary, NC). The statistical analysis includes the analysis of variance (ANOVA) where ‘SS’ is the sum of squares of the deviations from the means, ‘df’ is the degrees of freedom, and ‘MS’ is the mean squares. ‘F-stat’ is the ratio of two variances used to find out if the means between two populations are significantly different. ‘p-value’ is the probability of obtaining test results (at least as extreme as the results actually observed during the test, assuming that the null hypothesis is correct). For the one-way ANOVA, p-values less than 0.05 were considered statistically significant. All of the data are also presented as average ±standard deviation.

Results and discussion

Antibacterial activity

The human body produces complex electrical activity in many different types of cells, including neurons, endocrine and muscle cells, called “excitable cells.” This electricity also creates a magnetic field. The space surrounding a charged object is affected by the presence of the charge thus, resulting in the establishment of an electric field in that space.

The newly designed fabrics have provided longer conductive barriers (electromagnetic shielding). When microbes such as bacteria, and viruses enter the fiber, electric fields are generated by human movements through the attraction and repulsion of electric charges.³⁹ The designed fabric will convert the expansion and contraction generated by the wearer’s motion (waving hands, walking, and running, etc.) into electricity and kill microbes without the need for chemical finishes, as presented in cross-section images of fibers and fabrics in Figure 2.

Figure 2.

Cross-section images and a schematic diagram for the antimicrobial activity test of PET/MWCNT electronically conductive polymers.

The antibacterial properties of the control (unsterilized 100% PET fabric) and PET/MWCNT samples are presented in Figures 3 and 4. The total population of Staphylococcus aureus (S. aureus) ATCC 6538 and Escherichia Coli (E. coli) ATCC 25922 on each sample was determined. After the antibacterial tests were performed, the live vibrio concentration of the standard blank sample at zero contact time was compared with that of a standard blank sample oscillated for 24 h and that of the antibacterial fabric sample oscillated for 24 h. The effects of contact time on percentage reduction of bacteria with PET/MWCNT fabrics against E. coli and S. aureus are shown in Figures 3 and 4. It is seen that the percentage reduction of S. aureus before washing is lower than that of E. coli. This may be attributed to the fact that the Gram-positive cell wall consists of linear ester linkages cross-linked with short peptides of bacteria to form a three-dimensional rigid structure.⁴⁰ However, a small but a statistically significant increase was observed with the increase in carbon nanotube nanoparticle concentration (from 94% to 99% for S. aureus and from 96% to 99% for E. coli). It is attributed to the antibacterial effects of MWCNT, causing a small significant increase with increasing concentration.

Figure 3.

Antibacterial activity using S. aureus ATCC 6538. The data are represented as mean ± standard deviation (SD).

Figure 4.

Antibacterial activity using E. coli ATCC 25922. The data are represented as mean ± standard deviation (SD).

Since AATCC 100 test method is a quantitative test method, reliable test results were obtained about the antibacterial activity on Gram-positive S. aureus and Gram-negative E. coli. Although the antibacterial mechanism of MWCNT is not yet understood, it is believed that they have a germicidal power on Gram-positive bacteria according to the reported values on such inorganic nanoparticles.⁴¹ Although covalently bonded metal ions to ester chains provided a stable and excellent antibacterial activity, the growth rate of S. aureus and E. coli decreased with increasing wash cycles, showing the weakening of the bonds. Therefore, the durability of the antibacterial fabrics was satisfied even after 20 wash cycles. The antibacterial effect of MWCNT against E. coli was less durable to washing than S.aureus, and the effectiveness of MWCNT against E. coli decreased to approximately 50% after 20 washes, which could be due the presence of the outer membrane.⁴²

Cytotoxicity testing

The cytotoxicity of sterilized raw PET fabric and PET/MWCNT fabrics was evaluated through the MTS test. The extraction medium was cultured with mouse fibroblast cells (L929) for 24, 48 and 72 h. As shown in Figure 5, the raw polyester fabric showed no significant difference from the control cells at 24 h as well as at 48 and 72 h. It could be seen that the viability of cells treated with PET/MWCNT fabrics was 98%, 96%, and 95% of the negative control at 24 h, 80%, 79% and 78% of the negative control at 48 h, 84%, 83% and 81% of the negative control at 72 h for sample A, B and C, respectively. The viability of cells treated with raw polyester fabric was slightly higher than that of PET/MWCNT. Generally, samples C with higher MWCNT content showed a higher percentage of cell viability in comparison with samples A with lower MWCNT contents. According to the MTS reading, most of the samples stimulate the cell growth rapidly. As reported before, the average relative cell viability was over 70%, indicating the low toxicity of PET/MWCNT material.^43–46 These results indicated that the PET/MWCNT fabric had low toxicity to L929 cells.

Figure 5.

In vitro cytotoxicity tests of L929 cells cultured in extracts of raw polyester fabric and PET/MWCNT fabrics for 24, 48 and 72 h. The data are represented as mean ± standard deviation (SD).

Electromagnetic shielding effect

The highest and the lowest shielding effect frequencies were used as reference values. The mean shielding effect values were calculated and the results were evaluated using Table 3. The definition of screening effectiveness (SE) is directly related to an infinitely spread screening layer. The results of SE measurements depend on the method, frequency range, size of the sample, and the properties of the material itself.

Table 3.

Electromagnetic shielding reference limits for the evaluation.

SE (dB)	% Decrease in electric field	Evaluation
0–10	0–68.377	No shielding effect
10–30	68.377–99.838	Simple shielding
30–60	99.838–99.900	Normal shielding
60–90	99.900–99.997	Adequate shielding
90–120	99.997–99.999	Almost perfect shielding
120 and above	99.999 and above	Maximum shielding

Mean SE value of raw PET fabrics was determined as 3.70 dB. The mean SE values of PET/MWCNT powernet fabrics were found in the range of 22.79 dB–25.77 dB at the frequency of 0–1.30 GHz. The highest SE was measured as 35.29 dB for type C (30% MWCNT concentration) at 86 MHz frequency and the results are presented in Table 4. A small but statistically significant increase was observed with the increase in MWCNT content. This could be due to the longer conductive path of PET/MWCNT fibers, which provides better conductive network to the fabrics. When the fabrics were evaluated according to the FTTS-FA-003 standard, it was observed that they would provide a simple shielding in general use class, provide moderate protection and the newly designed fabrics would help sensing and actuation.

Table 4.

Electromagnetic shielding results.

PET/MWCNT	A	B	C
Max. SE value	32.17 dB	33.04 dB	35.29 dB
Min SE value	13.42 dB	14.60 dB	16.25 dB
Mean SE value	22.79 dB	23.82 dB	25.77 dB
Standard deviation	0.17	0.19	0.21

Differential scanning calorimetry

According to the results presented in Figure 6 and the graphics obtained from DSC curves, the melting temperature was measured as 250.9^oC, 249.5^oC, and 249.1^oC for samples A, B and C, respectively. It is concluded that the carbon nanotube nanoparticles have lowered the melting temperature of PET from 260^oC to around 249.5^oC. A small but statistically significant decrease in melting temperature was observed with the increase in carbon nanotube nanoparticle concentration in the structure. It can be concluded that the new materials would provide advantages during processes such as dyeing and other treatments by energy savings in the future.

Figure 6.

DSC analysis for each specimen versus % content in MWCNT nanoparticles. (Sample A: 20 wt.% MWCNT, Sample B: 25 wt.% MWCNT, Sample C: 30 wt.% MWCNT)

Stiffness

All fabrics have shown good elasticity according to the reported results presented in Figure 7. The stiffness showed a small but statistically significant decrease for all fabrics with the increase in MWCNT concentration and after 10 and 20 washes. The increase in MWCNT content created more elastic structures. It was also observed that the increase in the filler content exhibited higher elastomeric performance on the polyester resin embedded with nanoparticles.⁴⁷ It is thought that the MWCNT nanoparticles decreased the crystallinity and increased the amorphous structure yielding an increase in the elastic structure of the fabric. Higher percentages of nanoparticles have created more amorphous structures bringing more elasticity into the structure. According to the results, the newly designed pressure garments would provide flexibility and comfort to help muscle training during long use in rehabilitation.

Figure 7.

Stiffness (MD, machine direction; CD, cross direction; W, wash) for each specimen versus % content in MWCNT nanoparticles. (Sample A: 20 wt.% MWCNT, Sample B: 25 wt.% MWCNT, Sample C: 30 wt.% MWCNT).

ANOVA one-way was used to analyze the effect of MWCNT on stiffness. Using one-way analysis of variance, the p-value was found as 0.02. The result of the analysis is shown in Table 5. As the p-value is smaller than 0.05, it can be suggested that MWCNT concentration has a statistically significant effect on stiffness.

Table 5.

ANOVA and estimation of parameters from stiffness.

ANOVA summary
Source of variance	SS	df	MS	F-stat	p-value
Between groups	42	2	21	4.4213	0.00232
Within groups	113.9948	24	4.7498
Total	155.9948	26

Pressure measurements

Exerted pressures were measured using wireless pressure sensors between 5.3 and 5.7 mmHg for the ankle and 4.9–5.2 mmHg for the calf, which are within the required medical range. The results are presented in Figure 8. Exerted pressures showed a small but statistically significant increase with the increase in MWCNT concentration and after 10 and 20 washes. It is thought that the increase in nanoparticle concentration decreased the crystallinity and thus the amorphous structure increased, creating a more elastic structure. Wash cycles also significantly increased the elasticity of the fabrics.

Figure 8.

Exerted pressures (mmHg) (A, Ankle; C, Calf; W, Wash) for each specimen versus % content in MWCNT nanoparticles. (Sample A: 20 wt.% MWCNT, Sample B: 25 wt.% MWCNT, Sample C: 30 wt.% MWCNT).

It is important to note that statistical analysis demonstrated that these mean values were not significantly different. From the analysis of variance and estimation of parameters effect summarized in Table 6, it was found that MWCNT concentration has a statistically significant effect on the final pressures (p < 0.05).

Table 6.

ANOVA and estimation of parameters from final pressures.

ANOVA summary
Source of variance	SS	df	MS	F-stat	p-value
Between groups	0.4657	2	0.2329	4.774	0.00151
Within groups	1.6097	33	0.0488
Total	2.0754	35

Conclusion

In this study, highly elastic conductive PET/MWCNT powernet fabrics were produced from MWCNT integrated melt-spun PET yarns and their antimicrobial properties was investigated in terms of microbe killing mechanism with the help of electric fields and the highly elastic structure.

Results showed that MWCNT has a statistically significant effect on antibacterial activity, cytotoxicity, electromagnetic shielding, stiffness, and exerted pressures. PET/MWCNT powernet fabrics showed excellent antibacterial activity against tested germs. A small but a statistically significant increase was observed with the increase in MWCNT concentration (from 94% to 99% for S.aureus and from 96% to 99% for E. coli) and 30 wt.% MWCNT samples showed better antibacterial activity. In addition, the antibacterial effect of MWCNT against E. coli was less durable to washing than S.aureus, and the effectiveness of MWCNT against E. coli decreased to approximately 50% after 20 washes, indicating good laundering durability of the antibacterial fabrics. In terms of cytotoxicity tests, the PET/MWCNT samples were found to be toxic-free without interrupting the cell line and primary cell growth in vitro and samples with higher MWCNT content showed a higher percentage of cell viability in comparison with samples with lower MWCNT contents. All samples with continuous MWCNT fillers have shown a good electromagnetic shielding effect in the range of 22.79–25.77 dB at the frequency of 0–1.30 GHz and classified in the general use class with providing very good protection according to the standard of FTTS-FA-003. The highest SE (35.29 dB) was achieved with 30% concentration of MWCNT at 86 MHz frequency. Thus, the materials have provided longer conductive networks and formed electromagnetic shielding. According to DSC analyses, it was observed that the MWCNT decreased the crystalline density (crystallinity) of PET fibers, resulting in a lower melting temperature of the samples. The stiffness showed a small but statistically significant decrease for all fabric samples with the increase in MWCNT concentration. MWCNT nanoparticles decreased the crystallinity and increased the amorphous structure, creating a more elastic structure with excellent conductivity. Exerted pressures showed a small but statistically significant increase with the increase in MWCNT concentration and the newly designed pressure garments would provide flexibility and comfort to help muscle training during long use in rehabilitation.

In the future, the new materials would provide advantages during processes such as dyeing and other treatments by energy savings and being environmentally friendly. Finally, the manufactured PET/MWCNT materials will convert the expansion and contraction generated by the wearer’s motion into electricity, killing microbes without the need for chemical finishes while providing a long elastic and strong structure with a close fit to help sensing and actuation. They would also provide a durable antimicrobial activity and an electromagnetic shielding effect during long continuous use for future designs. Future studies will focus on different fabric structures with different nanoparticle concentrations and different germs considering the circular economy principles by following ecological methods.

Supplemental Material

Supplemental Material - Antimicrobial Properties of Highly Elastic Conductive Poly(ethylene terephthalate)/Multiwalled Carbon Nanotube Fabrics

Supplemental Material forAntimicrobial Properties of Highly Elastic Conductive Poly(ethylene terephthalate)/Multiwalled Carbon Nanotube Fabrics by Nilüfer Y Varan, Pelin Altay and Yavuz Çaydamlı in Journal of Industrial Textiles

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iDs

Nilufer Y Varan

Pelin Altay

Supplemental Material

Supplemental material for this article is available online.

References

Allcock

Lampe

. Contemporary Polymer Chemistry. Englewood Cliffs, NJ: Prentice-Hall, 1990.

Chen

Jiang

. A review on conversion of crayfish-shell derivatives to functional materials and their environmental applications. J Bioresources Bioproducts 2020; 5(4): 238–247.

Dalton

Collins

Munoz

Super-tough carbon-nanotube fibres. Nature 2003; 423: 703.

Alimohammadi

Gashti

Mozaffari

. Polyvinylpyrrolidone/carbon nanotube/cotton functional nanocomposite: preparation and characterization of properties. Fiber Polym 2018; 19: 1940–1947.

Lachman

Bartholome

Miaudet

, et al. Raman response of carbon nanotube/PVA fibers under strain. J Phys Chem C 2009; 113: 4751–4754.

Wang

Deo

Poulin

, et al. Carbon nanotube fiber microelectrodes. J Am Chem Soc 2003; 125: 14706–14707.

Dalton

Collins

Razal

, et al. Continuous carbon nanotube composite fibers: properties, potential applications, and problems Electronic supplementary information (ESI) available: frontispiece figure. J Mater Chem 2004; 14: 1.

Jeon

Jeong

. Preparation and properties of polypropylene nanocomposites reinforced with exfoliated graphene. Fiber Polym 2012; 13: 507–514.

Wang

Tang

, et al. Ecofriendly electrospun membranes loaded with visible-light-responding nanoparticles for multifunctional usages: highly efficient air filtration, dye scavenging, and bactericidal activity. ACS Appl Mater Inter 2019; 11(13): 12880–12889.

10.

Sulong

Park

Azhari

, et al. Process optimization of melt spinning and mechanical strength enhancement of functionalized multi-walled carbon nanotubes reinforcing polyethylene fibers, Composites Part B: Eng 2011; 42(1): 11–17.

11.

Xia

Zhang

, et al. Processing and valorization of cellulose, lignin and lignocellulose using ionic liquids. J Bioresources Biproducts 2020; 12(2): 79–95.

12.

Liang

Cao

, et al. Blow-spun nanofibrous composite Self-cleaning membrane for enhanced purification of oily wastewater. J Colloid Interf Sci 2022; 608: 2860–2869.

13.

Zhang

Cui

, et al. Hydrothermal synthesized UV-resistance and transparent coating composited superoloephilic electrospun membrane for high efficiency oily wastewater treatment. J Hazard Mater 2020; 383: 121152.

14.

Shin

Lee

Kim

, et al. Synergistic toughening of composite fibres by self-alignment of reduced graphene oxide and carbon nanotubes. Nat Commun 2012; 3: 650.

15.

Anand

Jose

Agarwal

, et al. PET-SWNT nanocomposite fibers through melt spinning. Int J Polymeric Mater 2010; 59(6): 438–449.

16.

Anand

Agarwal

Joseph

. Preparation and characterization of solution cast films of PET, reorganized PET and their MWNT nanocomposites. J Appl Polym Sci 2007; 104: 3090–3095.

17.

Zhang

Zhao

, et al. Cobalt induced growth of hollow MOF spheres for high performance supercapacitors. Mater Chem Front 2021; 5: 4981–5491.

18.

Zhang

Zhao

Song

, et al. UV-fluorescence probe for detection Ni2+ with colorimetric/spectral dual-mode analysis method and its practical application. Bioorg Chem 2021; 114: 105103.

19.

Liu

Zeng

Hofmann

, et al. Antibacterial activity of graphite, graphite oxide, graphene oxide, and reduced graphene oxide: membrane and oxidative stress. ACS Nano 2011; 5: 6971–6980.

20.

Zhou

Forman

, et al. Multi-walled carbon nanotubes: A cytotoxicity study in relation to functionalization, dose and dispersion. Toxicology in vitro 2017; 42: 292–298.

21.

Seo

Hwang

Kim

, et al. Antibacterial activity and cytotoxicity of multi-walled carbon nanotubes decorated with silver nanoparticles. Int J Nanomedicine 2014; 9: 4621.

22.

Avilés

Cauich-Rodríguez

Moo-Tah

, et al. Evaluation of mild acid oxidation treatments for MWCNT functionalization. Carbon 2009; 47, 2970–2975.

23.

Kang

Herzberg

Rodrigues

, et al.

Antibacterial effects of carbon nanotubes: size does matter!

Langmuir 2008; 24: 6409–6413.

24.

Olivi

Zanni

De Bellis

, et al. Inhibition of microbial growth by carbon nanotube networks. Nanoscale 2013; 5: 9023.

25.

Al-Ghamdi

Al-Hartomy

Al-Solamy

, et al. Correlation between electrical conductivity and microwave shielding effectiveness of natural rubber based composites, containing different hybrid fillers obtained by impregnation technology. Mater Sci Appl 2016; 7: 496–509.

26.

Mattsson

Ahlbomi

Bridges

, et al. Possible effects of electromagnetic fields (EMF) on human health, scientific committee on emerging and newly identified health risks SCENIHR, 2007.

27.

Reynolds

. U.S. Patent, 3164840, 1965.

28.

, et al. Crystallization and thermal behavior of multiwalled carbon nanotube/poly(butylenes terephthalate) composites, Polym Eng Sci 2008; 48: 1057–1067.

29.

Mazinani

Ajji

Dubois

. Structure and properties of melt-spun PET/MWCNT nanocomposite fibers. Polym Eng Sci 2010; 50(10): 1956–1968.

30.

Luo

Wei

, et al. Microstructure of carbon nanotubes/PET conductive composites fibers and their properties. Composites Sci Technol2006; 66(7–8): 1022–1029.

31.

Sandler

JKW

Pegel

Cadek

, et al. A comparative study of melt spun polyamide-12 fibres reinforced with carbon nanotubes and nanofibres. Polymer 2004; 45(6): 2001–2015.

32.

Bhattacharyya

Sreekumar

Liu

, et al. Crystallization and orientation studies in polypropylene/single wall carbon nanotube composite. Polymer 2003; 44(8): 2373–2377.

33.

Zhao

Zhang

, et al. Low percolation thresholds of electrical conductivity and rheology in poly(ethylene terephthalate) through the networks of multi-walled carbon nanotubes. Polymer 2006; 47: 480–488.

34.

Alimohammadi

Gashti

Shamei

. Functional cellulose fibers via polycarboxylic acid/carbon nanotube composite coating. J Coat Technol Res 2013; 10: 123–132.

35.

Sivasubramaian

Vhanbatte

Kadole

. Conducting Polymer/CNT Coated Flexible Electrode for Supercapacitors. International Journal of Engineering Research and Technology (IJERT) 2012; 1(6): ISSN: 2278–0181.

36.

Lin

J-H

Lin

Z-I

Pan

Y-J

, et al. Manufacturing techniques and property evaluations of conductive composite yarns coated with polypropylene and multi-walled carbon nanotubes. Composites Part A: Appl Sci Manufacturing 2016; 84: 354–363.

37.

Arbab

Sun

Sahito

, et al. Multiwalled carbon nanotube coated polyester fabric as textile based flexible counter electrode for dye sensitized solar cell. Phys Chem Chem Phys 2015; 17: 12957–12969.

38.

Yang

Liu

, et al. Long-term antibacterial protected cotton fabric coating by controlled release of chlorhexidine gluconate from halloysite nanotubes. Rsc Adv 2017; 7: 18925.

39.

Dabrowska

Greszta

. Analysis of the possibility of using energy harvesters to power wearable electronics in clothing. Adv Mater Sci Eng 2019; 2019: 1687–8434.

40.

Auer

Weibel

. Bacterial cell mechanics. Biochemistry 2017; 56: 3710–3724.

41.

Mohseni

Aghayan

Ghorani-Azam

, et al. Evaluation of antibacterial properties of Barium Zirconate Titanate (BZT) nanoparticle, Braz J Microbiol 2014; 45: 1393–1399.

42.

Silhavy

Kahne

Walker

. The bacterial cell envelope. Cold Spring Harbor Perspectives Biol 2010; 2(5): a000414.

43.

Kangwansupamonkon

Lauruengtana

Surassmo

, et al. Antibacterial effect of apatite-coated titanium dioxide for textiles applications. J Nanomed Nanotechnol 2009; 5: 240–249.

44.

Acosta

Novak

Rojas

, et al. BaTiO₃-based piezoelectrics: Fundamentals, current status, and perspectives. Appl Phys Rev 2017; 4: 041305.

45.

Yuan

Cheng

, et al. Biocompatible nanogenerators through high piezoelectric coefficient 0.5Ba(Zr_0.2Ti_0.8)O₃-0.5(Ba_0.7Ca_0.3)TiO₃Nanowires for in-vivo applications. Adv Mater 2014; 26: 7432–7437.

46.

Cheng

Yuan

, et al. Wireless, power-free and implantable nanosystem for resistance-based biodetection. Nano Energy 2015; 15: 598–606.

47.

Asimakopoulos

Psarras

Zoumpoulakis

. Barium titanate/polyester resin nanocomposites: development, structure-properties relationship and energy storage capability. EXPRESS Polym Lett 2014; 8: 692–707.

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