Electrical Characterization of Graphene Nanoparticles Conductive Ink using Thermoplastic Polyurethane (TPU)
Substrate
Hartini Saad1*, Ahmad Noor Syimir Fizal 2, Mohd Azli Salim3, Muhd Ridzuan Mansor3 Ahmad Naim Ahmad Yahaya2
1 Sekolah Kejuruteraan dan Sains Kreatif, Kolej Yayasan Pelajaran Johor, KM 16, Jalan Kulai- Kota Tinggi, Johor, Malaysia.
2 Universiti Kuala Lumpur, Malaysian Institute of Chemical and Bioengineering Technology (MICET), Taboh Naning, 78000 Alor Gajah, Melaka, Malaysia.
3 Fakulti Kejuruteraan Mekanikal, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, Malaysia.
*Corresponding Author: [email protected]
Accepted: 15 July 2021 | Published: 1 August 2021
___________________________________________________________________________
Abstract: Conductive ink is used as interconnecting tracks to create conductive paths. This research main objective is to utilised composite materials for conductive ink which to enhanced the production of making conductive ink which has good engineering properties in terms of electrical conductivity and cleaner productions. Thermoplastics viscous paste used as conductive materials to enlarge the capability of conductive ink to conducts electricity. The conductive ink applications offer many opportunities of carbon nanomaterial purposely for printed, stretchable and flexible electronics. Graphene nanoparticles conductive ink used as the connection material, fabricated on thermoplastic polyurethane (TPU) using manual stencil method for straight line, curve, square and zigzag pattern to investigate the effect of sheet resistivity for all the pattern state above. The samples used fix circuit width of 1mm, 2mm and 3mm. The ASTM F390 four-point probe used to measure the values of sheet resistivity. Results of this study displayed that 1 mm width samples provided the lowest value of sheet resistivity while, the higher values was displayed by 2 mm width samples nearly all the patterns.
Keywords: graphene nanoparticles, thermoplastic polyurethane (TPU), circuit pattern __________________________________________________________________________
1. Introduction
Main purpose of conductive ink used as interconnect to create conductive portion. The conductive nanomaterials are introduced to produce best electrical conductivity of conductive inks and the sizes of the nanomaterials to avoid clogging the printed head (Roberson et al., 2011). Inkjet printing technology on polydimethylsiloxane (PDMS) substrates allow for the patterning of silver conductive lines (Abu-Khalaf et al., 2018). There are no research has been reported on how to patterning a graphen nanoparticles conductive patters for lines, curve, square and zigzag pattern on thermoplastic polyurethane (TPU) substrate using manual stencil printing. Other reasons to replace the other carbon materials inks with graphene conductive inks because graphene have the potential to reform the printed conductor field. This paper investigate effect of sheet resistivity at different patterns and width size using graphene nanoparticles conductive ink and printed on thermoplastic polyurethane (TPU) substrate.
2. Literature Review
Electrical conductivity in Printed Electronic (PE) is very significant to conductive ink.
Conductive inks used as interconnect to create conductive path in traditional function (Agcayazi et al., 2018). Conductive inks become a new innovation because of the processes produce less corrosion effect and low cost (Li et al., 2018), lightweight and easiness is main advantage to be adapted in electronic packaging industries (Wan et al., 2020). Due to electrical properties and capability to conduct electricity, graphene and carbon nanotubes was choose as a conductive ink (Fernandes et al., 2020). Another advantage of graphene is the flow of free electrons can travel without being dispersed (Haque et al., 2018). Peculation / infiltration threshold theory is often used to explain the electrical conductions mechanism. The composite properties on electrical conductivity was affected by the infiltration threshold which increases the loading and magnitude to certain point (Kumar et al., 2019). The insulator in the composite was restructured to become conductors due to the electron movements after changes of the loading. Figure 1 show when the composite attain the infiltration threshold which causes the conductive filler to rise steadily (Mei et al., 2021). The electrical conductivity of the composite will be enhanced in various order of angle after the composite was restructured into conductive materials after attaining infiltration threshold (Alemour et al., 2018).
Figure 1: Dependency of electrical conductivity on filler loading (Alemour et al., 2018)
Table 1 displayed the carbon-based materials reinforced of infiltration threshold of various polymer resins. The infiltration threshold indicate the changes of borderline between insulator substance and conductive substance (Kargar et al., 2018). Ram et al. (2019), the conductive filler shape and size depending on percolation threshold. The minimal infiltration threshold on graphene composite cause by low density and lightweight material of graphene (Yoonessi et al., 2017). By adding enough graphene into the formulation, the conductivity level becomes higher and infiltration becomes very small resulting the electron to move to other location (Konsta-Gdoutos et al., 2010).
Table 1: Carbon -based infiltration threshold
Materials infiltration threshold
(vol%) Functionalized graphene filled epoxy composites 0.10
Epoxy nanocomposite/ neat graphene 0.53
Polyethylene composite / graphene 0.07
Polybutylene terephthalate 0.7
The polyethylene terephthalate (PET) nanocomposite/ graphene 0.47 Thermally reduced graphene oxide (TRGO) <0.5
Graphite >2.7
PS/ Graphene composites 0.10
Reduced graphene oxide (RGO) /PVC/ vinyl nanocomposite 0.15
Polybutylene terephthalate nanocomposite 0.47
(Alemour et al., 2018)
3. Methodology
Printed electronics industry mostly used conductive inks to print electrical circuit. The conductive ink is contained of complex formulation of different components such as carbon particles, metal or conductive polymers. Mechanical and adhesive properties produced from the dispersion of conductive particles by Bisphenol-A (BPA) resins and tetraethylenepentamine (TETA) are mix to dissolve the (BPA) to manage rheological behavior functional of the ink properties. The graphene nanoplatelets, GNPs developed by Sigma Aldrich weight of 250 g, molecular mass of 12.01 g/mol and surface area of 500 m2/g. The optimized mixing ratio of bisphnol A : TETA : GNP 100: 30 : 35 wt% filler loading throughout the study as reported in previous study by author (Salim et al., 2020). Direct mixing process was chosen to produce the conductive ink for cleaner production and environmental preservation. Commercial thermoplastic polyurethane (TPU) available on the market was chosen to be used as a substrate as they are very stretchable in nature. The printing method of manual screen printing was used and the printing material used is graphene based conductive ink. This material used to print in four different test patterns with thickness of the test pattern sample was set at 1mm, 2mm and 3mm. The Evaluation of sheet resistivity were according to ASTM E2546-1 methods. Electrical properties and characterization was done on the composite to determine the best test pattern and width to be printed on TPU substrate. The in-line four point probes was performed to see the sheet resistance of the conductive ink with the reference standards of ASTM F390.
Figure 1: Sample Patterns of Conductive Ink’s
Figure 2: Conductive ink’s actual test patterns
Pattern 4
Pattern 1 Pattern 2
1 mm
2 mm
3 mm
1 mm
2 mm
3 mm
3 mm 3 mm
2 mm 2 mm
1 mm
1 mm R7.88 R7.13
R7.50 R5.50
R4.88 R6.13
45°
60°
75°
Pattern 3
4. Discussion
Discussion
Table 2 displayed the graphene nanoparticles sheet resistivity values at different width and patterns. Both width and pattern contain three measurement points to obtain the reading consistency of printed graphene ink. The best error bar can be determined by referring to the lowest reading of the standard deviation. From the same table, large standard deviations consist at 2mm width for three types of patterns, straight line, curve and square pattern and zigzag pattern consist large standard deviation at 3 mm width. The results indicate that the data have the highest average resistivity. Graph at 1 mm width, of curve, zigzag and straight line pattern obtained a small readings of standards deviation. The same results obtained at 3mm width of square pattern. The small readings of error bar displayed that the data is accumulated nearly throughout the mean and the results reveal that for those patterns mentioned for 1mm and 3mm width state the smallest and reliable mean resistivity. The straight line sample pattern showed the lowest mean resistivity value compared to three other patterns. 1 mm sample width displayed the lowest sheet resistivity value while 2 mm sample width displayed the highest sheet resistivity value for most of the patterns samples. This study findings illustrate that the sheet resistivity has a linear relationship with the sample pattern and width where the sheet resistivity of the pattern decreased when the width of the pattern was decreases. The value of sheet resistivity was analysed based on the track width of the four types of patterns mentioned before. According to the trend for zigzag pattern, the smaller the width, the value of sheet resistivity decreases. If the width is bigger, the value of sheet resistivity values will increase (Saad et al., 2020).
Table 2: Resistivity for graphene nanoparticles
Pattern Width (mm) Point Average sheet resisitivity (Ω/sq)
Straight line 1 1 55597.440
2 79634.270
3 79469.587
2 1 454690.375
2 470436.950
3 383554.350
3 1 261700.750
2 428529.360
3 338419.200
Curve 1 1 268929.975
2 124686.350
3 175319.500
2 1 737077.000
2 294098.380
3 712855.750
3 1 403746.200
2 411043.350
3 231469.700
Square 1 1 135473.445
2 130539.613
3 157319.608
2 1 631907.200
2 917675.050
3 342459.600
3 1 180434.850
2 366091.020
3 464622.520
Zigzag 1 1 69441.675
2 150092.758
3 71370.200
2 1 196585.300
2 184604.647
3 319851.467
3 1 1007824.450
2 925244.117
3 1077955.867
Figure 2, shows straight line width of 1mm has smallest and balance average readings of sheets resistivity and also smallest readings of the standard deviation readings. This obtained that the data accumulated nearly at the midpoint values. According to Phillips et al.,(2017) the increasing of the ratio , the lower content of carbon ink caused less conductive.
Figure 2: Sheet resistivity for straight line pattern of different width
The sheet resistivity of 1mm and 3mm width displayed low readings and readings of 2mm width displayed highest sheet resistivity readings. As discussed earlier, the lower value of sheet resistivity depends on the nature of the material, the increase and decrease of the sheet resistivity depend on the features of the material and the physical pattern affects the resistance of the samples (Saad et al., 2020). The electrical conductivity of graphene inks performance depend on lowest value of standard deviations.
0.000 100000.000 200000.000 300000.000 400000.000 500000.000 600000.000 700000.000
1 2 3
Sheet resistivity (Ω/ sq)
Point
1mm 2mm 3mm
Figure 3: Sheet resistivity for curve pattern of different width
Generally, the conductivity of the material decreases by increasing the ink of the sheet resistivity. The graph of 1mm width in Figure 4 displayed the lowest readings of sheet resistivity. According to Khuzaimah et al., (2018) a significant difference between resistivity of 1 mm circuit width to the other circuit width was also noticed from the experimental results, indicating lower electrical conductivity performance by commercial conductive paste when thinner circuit width is applied. This illustrate data is accumulated nearly the midpoint. Results obtain at 2mm width readings displayed the highest rate of sheet resistivity readings. It can be conclude that data of 2mm width disperse generally from the midpoint and indicates the highest midpoint readings.
Figure 4: Sheet resistivity for square pattern of different width
Figure 5 show the minimum sheet resistivity displayed at 1mm width and 3mm width displayed the maximum readings of sheet resistivity. The relationship shows that sheet resistivity of the pattern decline when the width of the pattern is rise. According to Saad et al., (2020) sheet resistivity rise by expending the width of the samples from 1 mm to 2mm width and sheet resistivity decline slightly at 3mm width. Based on these observations, the best achievements of electrical conductivity at 1mm width for zigzag pattern.
0.000 200000.000 400000.000 600000.000 800000.000 1000000.000 1200000.000
1 2 3
Sheet Resistivity (Ω/sq)
Point
1mm 2mm 3mm
0.000 200000.000 400000.000 600000.000 800000.000 1000000.000 1200000.000 1400000.000
1 2 3
Sheet Resistivity (Ω/sq)
Point
1mm 2mm 3mm
Figure 5: Sheet resistivity for zigzag pattern of different width
The minimum readings of the graph were observed at the straight line pattern. This illustrate that the lowest sheet resistivity of 1 mm width at straight line shape and zigzag shape displayed the maximum sheet resistivity readings of the graph. The similar findings was recorded where it is observed that at 1mm width of straight line give the lowest values and obtained that the smaller the width, the value of sheet resistivity will decreases because the resistance is the opposite to the flow of electrons through the substance in response to the correlated voltage (Saad et al., 2020). The best performance of electrical conductivity from results obtained is straight line shape.
Figure 6: Sheet resistivity for 1 mm width of the different pattern
The graph of sheet resistivity at a different pattern for 2 mm of width illustrate in Figure 7. The zigzag pattern display the lowest graph of sheet resistivity. The observation of the results displayed that zigzag pattern of sheet resistivity decreased with the increasing of the width. The results reveal that the best performance of electrical conductivity for 2 mm width is zigzag pattern. Referring to the previous paper, the sheet resistivity of zigzag shape decreases by increase of the width and the performance of a printed line is direct by its pattern (Phillips et al., 2017).
0.000 500000.000 1000000.000 1500000.000 2000000.000
1 2 3
Sheet Resistivity (Ω/sq)
Point
1mm 2mm 3mm
0.000 50000.000 100000.000 150000.000 200000.000 250000.000 300000.000 350000.000 400000.000
0 0 . 5 1 1 . 5 2 2 . 5 3 3 . 5
Sheet Resistivity (Ω/sq)
Point
straight curve square zigzag
Figure 7: Sheet resistivity for 2 mm width of the different pattern
The results of the graph show the sheet resistivity for the square pattern show the smallest readings compared to others patterns. The 3 mm width for the square pattern gives the best performance of electrical conductivity because when sheet resistivity decreased the performance of electrical conductivity will increased. This obtained results reveal that the conductivity of the material is inverse to the resistivity.
Figure 8: Sheet resistivity for 3 mm width of the different pattern
Conclusion
The electrical characteristics of graphene nanoparticles conductive ink was observed on different patterns and width. The 1mm circuit width showed significant difference sheet resistivity compared to 2 mm and 3 mm circuit width. This revealed that the carbon-based conductive paste is more suited for wider-size circuit geometry application as compared to fine-size circuit geometry. The result analysis showed that the usage of graphene will increase the electrical performance of conductive ink making it suitable for extensive scale of function in electronic components, and electrodes for rechargeable batteries, electromagnetic shielding and capacitors in comparison to existing conductive ink in terms of the best achievement of electrical conductivity. Future study can be made to observe the difference in the mechanical and physical characteristics of graphene nanoparticles conductive ink which further optimized its usage on industrial sector.
0.000 200000.000 400000.000 600000.000 800000.000 1000000.000 1200000.000
0 0 . 5 1 1 . 5 2 2 . 5 3 3 . 5
Sheet Resistivity (Ω/sq)
Point
straight curve square zigzag
0.000 200000.000 400000.000 600000.000 800000.000 1000000.000 1200000.000 1400000.000 1600000.000 1800000.000
0 1 2 3 4
Sheet Resistivity (Ω/sq)
Point
straight curve square zigzag
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