Surfactant-assisted water-based graphene conductive inks for flexible electronic applications

https://doi.org/10.1016/j.jtice.2021.06.022Get rights and content

Highlights

  • DI/PVP graphene ink exhibit high wetting, good stability and electrical conductivity.

  • Electrical conductivity increased with increasing number of printing cycle.

  • Insignificant drop in conductivity (about 0.2%) when the bending force was released after 100 bending cycles.

Abstract

Background

Inkjet printing of graphene conductive inks plays a critical role in the technological advancement in flexible and stretchable electronics applications. In this study, water-based graphene conductive ink was fabricated and printed through inkjet printing on polyethylene terephthalate substrate.

Methods

Deionized (DI) water and three different types of surfactants (sodium dodecyl sulfate (SDS), polyvinylpyrrolidone (PVP), and Gum Arabic GA)) were utilized in the preparation of graphene conductive inks.

Significant Finding

Among other conductive ink formulations, graphene conductive inks fabricated using the DI/PVP surfactant exhibit relatively higher wetting and stability properties. In addition, this formulation led to an increment of about 80% in electrical conductivity compared to DI water-based conductive ink. The results revealed an improvement of about 50 times in the electrical conductivity of the printed film when the number of the printing cycle was increased from 1 to 10. Furthermore, it was observed that under 50% tensile strain, the graphene film prepared using the PVP surfactant exhibited only a 0.12% drop in electrical conductivity. Therefore, it is inferred that the conductive inks prepared from DI/PVP surfactants are highly suitable for use in flexible and wearable electronics.

Introduction

In recent years, there has been an increasing scientific interest in flexible and wearable printed electronics for the fabrication of wireless sensors for Internet of Things (IoT) technologies [1]. Printing techniques are employed to transfer an ink onto the substrate. The printing technology helps in the generation of tailored patterns of electrical properties on different substrates, such as polymers, silicon, textiles, and paper. Particularly, the use of polymer substrate facilitates the development of wearable electronic devices that are flexible and stretchable [2], [3], [4], [5]. In this regard, inkjet printing has attracted considerable attention owing to its applicability in the fabrication of flexible electronic devices [6,10].

Studies on different types of conductive inks and fillers for the fabrication of printed conductive patterns have been conducted. However, most of these studies heavily rely on carbon-based materials, such as graphene and carbon nanotubes [7,8]. Particularly, there are several reports on the successful development of graphene conductive inks and their application in printed electronics. In the fabrication process of graphene conductive inks, solvents are important to ensure suitable viscosity for ink printing. However, the choice of solvent for ink production is mainly dependent on the type of device used and the nature of the printing film. To date, various types of solvents, such as dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), ethanol, acetone, terpineol, and xylene, have been used to prepare graphene conductive inks [9]. However, some of these solvents, such as NMP and DMF, are harmful, have a high boiling point, and are not environmentally friendly. Conversely, an undesirable surface tension is often generated when graphene is dispersed in solvents with low boiling points, such as ethanol, acetone, and isopropanol.

Based on the importance of environmentally friendly conductive ink for humans and the environment, research trend is moving toward the minimization of the use of organic solvents. Therefore, the possibility of replacing these solvents with eco-friendly alternatives in the formulation of conductive inks is currently being widely investigated. In fact, the choice of suitable environmentally sustainable solvents has currently become an important point of focus. The most preferred solvent is water owing to its non-toxic nature and suitable boiling point. However, it has a high surface tension of 72.8 mJm−2 [17]. Moreover, the dispersion of graphene in water is difficult due to the hydrophobic character of graphite carbon. Therefore, surfactants are commonly utilized to improve graphene dispersion in graphene inks through van der Waals force, hydrogen bonding, electrostatic activity, and π–π interactions. Several surfactants have been incorporated in graphene suspensions, including ionic, non-ionic, and polymeric types [11]. Table 1 presents some of the previous studies on graphene conductive inks using various printing techniques. In the past, numerous researchers have studied graphene conductive inks using different kinds of solvent and water. In the table, some of the solvents (NMP and DMF) are toxic and not suitable for future printed flexible/wearable electronic applications. Moreover, the sheet resistance of a water-based ink is considered to be too high. Hence, a high (100°C–400°C) annealing temperature is often required to reduce the sheet resistance. Unfortunately, such a high annealing temperature is damaging for flexible polymer substrates. Because of this, environmentally friendly solvents that produce lower sheet resistance and require lower temperature for annealing conductive tracks are more desirable. An extensive review of several literatures revealed that only limited studies have been conducted to evaluate the performance of water-based graphene conductive inks.

Therefore, in this contribution, a comparison analysis of the properties of water-based and surfactant-assisted water-based graphene conductive inks is conducted. Different types of surfactants (sodium dodecyl sulfate (SDS), polyvinylpyrrolidone (PVP), and Gum Arabic (GA)) were utilized to facilitate the dispersion of graphene. Moreover, the conductive inks were printed through inkjet printing on polyethylene terephthalate (PET) substrate. The dispersion of graphene in the PVP surfactant conductive inks, the morphology, and the mechanical performance of the graphene conductive pattern were also investigated.

Section snippets

Materials

The important chemicals utilized in this study are SDS, PVP, and GA, which were supplied by Sigma-Aldrich. A DuPont Mylar A PET with a 125 μm thickness was used as the flexible substrate. The substrate has an opaque white appearance and used for inkjet printing.

Methods

An electrochemical exfoliation technique was employed to synthesize the graphene used in this study as previously reported [19]. The water-based graphene conductive inks were prepared by adding 0.5 wt% of graphene and 0.1 wt% of the

Results and discussion

The chemical structure and possible changes in the functional groups of the water-based graphene conductive inks with or without surfactants were investigated via FTIR analysis. The FTIR spectra of the water-based and surfactant-assisted water-based graphene conductive inks are presented in Fig. 2. The notable peak in the spectra of the water-based inks as presented in the figure is the broad and intense stretching vibration peak of the O–H bond at 3414 cm−1, which is due to the retained

Conclusion

In this research, graphene conductive inks were fabricated using deionized (DI) water with different types of surfactants (SDS, PVP, and GA). The stability, wettability, and electrical conductivity of DI/PVP-based graphene conductive inks were significantly higher than those of SDS- and GA-based graphene conductive inks. Specifically, the stability of DI/PVP-based graphene conductive inks resulted in high conductivity, which was sustained even up to about 1 month following the initial

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

The authors appreciate Universiti Sains Malaysia for providing the USM fellowship to the first author. We are also thankful to the Malaysia Ministry of Higher Education for the financial assistance through Research University Grant (grant no. 8014044). We would also like to thank the School of Materials and Mineral Resources Engineering, USM for the facilities.

References (35)

  • H. Wang et al.

    Mechanisms of PVP in the preparation of silver nanoparticles

    Mater Chem Phys

    (2005)
  • W. Zhang et al.

    Synthesis of Ag/RGO composite as effective conductive ink filler for flexible inkjet printing electronics

    Colloids Surf Physicochem Eng Asp

    (2016)
  • F. Torrisi et al.

    Graphene, related two-dimensional crystals, and hybrid systems for printed and wearable electronics

    Nano Today

    (2018)
  • R. Singh et al.

    Inkjet printed nanomaterial based flexible radio frequency identification (RFID) tag sensors for the internet of nano things

    RSC Adv.

    (2017)
  • J. Kim et al.

    Advanced materials for printed wearable electrochemical devices: a review

    Adv Electron Mater

    (2017)
  • A. Kamyshny et al.

    Conductive nanomaterials for 2D and 3D printed flexible electronics

    Chem Soc Rev

    (2019)
  • M. Gao et al.

    Inkjet printing wearable electronic devices

    J Mater Chem C

    (2017)
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