Elsevier

Materials Letters

Volume 264, 1 April 2020, 127332
Materials Letters

Characterization of AuNPs based ink for inkjet printing of low cost paper based sensors

https://doi.org/10.1016/j.matlet.2020.127332Get rights and content

Highlights

  • AuNPs based ink were synthesized and formulated with three varying [Au] of 300, 600 and 1200 ppm from USP.

  • Rheological, flow and wetting behavior of these inks were analyzed to find out the favorable one for inkjet printing.

  • Furthermore, it was characterized for size, shape, purity and optimum sintering conditions.

Abstract

The functionality of an effective metal NPs based ink in inkjet printing depends on its ability to achieve high mass concentration as well as suitable rheological properties for stable printability. In this work, AuNPs synthesized by USP were successfully formulated in inks of varying [Au] using PVP40 as stabilizer and DI water as solvent. The influence of the increasing [Au] on the rheological, flow and wetting behavior were investigated for requisite printable characteristics. Thermo-physical characterization was carried out on the optimized concentrated AuNPs ink using TGA, DLS, SEM and EDX techniques.

Introduction

Among the different metal nanoparticles (NPs) enriched inks, Gold nanoparticle (AuNPs) ink [1] remains the best choice for fabricating the patterns on different substrates (such as paper [2], polymer films [3] etc.) for flexible electronics [4] and sensing applications [5]. AuNPs ink has a high work function that helps it in demonstrating the superior stability and inertness when comes in contact with any aqueous media, biological fluids or living tissues, easy surface functionalization makes them the best choice for developing the low cost sensors.

But, the formulation of the AuNPs ink remains a challenge as the ink must meet certain physical, chemical and rheological properties [3], [6]. It should exhibit a well-controlled visco-elastic response for the smooth and optimized flow through the nozzles and then set immediately to facilitate the shape retention of the deposited feature [7]. Viscosity, surface tension (ST) and concentration are the basic essential parameters as well as the establishing criteria of the NPs enriched ink for effective printability through inkjet printing (IJP) [8]. IJP provides efficiency in terms of accurate deposition, minimal waste generation, cost-saving and quality of the fabricated devices as compared to other printing techniques [2]. The required viscosity and ST range for these inks were 0.002–0.03 Pa.s and 25–70 mN/m respectively for commercial available IJP printers with required fluency, high pattern quality of required resolution and without getting any clogs in nozzles [9]. While designing the NPs ink, these important points need to be kept in mind. Generally, the clustered NPs in the concentrated ink should be 1/100th of the size of the nozzle. The diameter of the nozzle opening in the cartridges in most of the commercial ink-jet printers were greater than 40 µm. In order to avoid the corrosion of the print head, it should be ensured that the AuNPs ink shall have pH value in the range of 4–9 [10]. Ultrasonic Spray Pyrolysis (USP) synthesis enables AuNPs to be synthesized in narrow size range and diverse shapes. This process can be easily and economically scalable to mass production [11]. Therefore, the printable AuNPs based inks can be commercially available for the fabrication of low cost paper based sensors. However, these metallic NPs inks for IJP would provide satisfactory printing results only with high stability in terms of jettability [12]. Thus, this work provides a detailed characterization with respect to mass concentration, viscosity and rheological properties of the formulated AuNPs based ink.

Section snippets

Materials

Gold (III) Acetate (Au(CH3COO)3, 99.9%, Alfa Aesar) Hydrochloric acid (HCl, 30% concentrated, Honeywell Fluka GmbH), Sodium Hydroxide (NaOH, 40 g/mol, Panreac AppliChem GmbH), Polyvinylpyrrolidone (PVP40, Avg. wt. 40,000, Sigma Aldrich), Nitrogen & Hydrogen gas (99.9%, Westfalen AG), DI water (purified with the Millipore system).

Synthesis and formulation of the AuNPs enriched ink

The preparation of the precursor solution of Au(CH3COO)3 and synthesis of AuNPs through USP were done as previously stated in M. Shariq et al. [13]. 500 ml of the synthesized AuNPs having [Au] = 80 ppm were rotavaporized (RC600, KNF Neuberger GmbH) to 50 ml. These AuNPs were further centrifuged (Mikro 200R, Hettich Centrifuge) with the help of AMICON Ultra −15 membrane filters (100,000 NMWL). The centrifuged concentrated AuNPs ink were further filtered through a 450 nm syringe filter to further

Measurement of rheological Properties: ST and viscosity

Wilhelmy plate method was used to determine ST with KRŰSS K12 tensiometer (Table 1). The flow and viscosity of AuNPs inks were measured by an Advanced Air Bearing Rheometer Bohlin Gemini 2 (Malvern Instruments) in the viscometery mode. (Measuring geometry: Cup and bob method).

This measured range of both viscosity and ST comes under the jettability window for most of the commercial ink-jet printers [14].

Viscosity vs shear stress

The yield shear stress (Ʈ0) is the minimum value required to break the internal structure of

Conclusions

The highly concentrated ink of 1200 ppm had shown the favorable rheological, flow and wetting behavior for commercial IJP. In future, this characterization framework shall provide a reliable reference for designing AuNPs inks in order to achieve high quality printing for low cost paper based sensors.

CRediT authorship contribution statement

Mohammed Shariq: Conceptualization, Methodology, Validation, Formal analysis, Writing - original draft. Somnath Chattopadhyaya: Writing - review & editing, Supervision. Rebeka Rudolf: Conceptualization, Writing - review & editing, Supervision. Amit Rai Dixit: Conceptualization, Methodology, Writing - review & editing, Supervision.

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.

Acknowledgements

The authors would like to acknowledge to EU-Erasmus Mundus Action2 Lot13 Euphrates Program between IIT(ISM), Dhanbad, India and University of Maribor, Faculty of Mechanical Engineering, Slovenia.

References (14)

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