Webinar: Microfluidizer Technology For Graphite Processing & Formulation of Graphene-Based Conductive Printing Inks

You are invited to join us for the latest free webinar from Microfluidics.

About the Speaker

• Research Associate, Nanomaterials & Spectroscopy Group – Cambridge Graphene Centre.
• Teaching Fellow, EPSRC Centre for Doctoral Training in Graphene Technology, and Bye-Fellow of Murray Edwards College.
• Particular interest lies in the chemistry and physics of nanomaterials including fullerenes, carbon nanotubes, graphene and the many other two-dimensional analogues.
• Current focus is on the scalable production of these enabling materials for mechanical, optical and electronic applications.

Dr. Stephen A. Hodge
Cambridge Graphene Centre, University of Cambridge, UK

Abstract

Graphene has potential for the realization of novel devices, such as printable antennas, touch screens and electrodes in (opto)electronic or storage devices [1-
3]. However, the current graphene production routes (sonication and high shearmixer) give low concentrations of few layer graphene (<0.2 mg/ml) [4] and require time consuming centrifugation to remove the non-exfoliated particles [4]. This webinar will explore the microfluidic exfoliation of graphite [5] in aqueous surfactant solutions (sodium deoxycholate) using a Microfluidizer processor at a shear rate of 8.6×107 s-1. Using a flow rate of 120 mL/min we can achieve 1 mg/mL single/few layer graphene (20% of single layer) with a production rate of 65 mg/h. This rate, for the same energy input (100 MJ/m3), starting graphite concentration (50 mg/mL) and volume (~200 mL) is 50% higher than reported values for a high-shear mixer [4] and 1500% times higher than sonication [4]. Unlike sonication or shear mixing, in Microfluidizer processor treatment all the material is uniformly exposed to intensive shear, thus the centrifugation step can be avoided and graphene nanoplatelets (GNPs) (mean thickness of 12 nm) can be produced (concentration of 80 mg/mL at a rate of 7.2 g/h). We use these to formulate conductive inks by adjusting the rheology for blade coating or screen printing (viscosity of hundreds of mPa.s). We employ sodium carboxymethylcellulose (CMC) as a binder and as rheology modifier, reducing the viscosity from 600 mPas at 100 s-1 to 160 mPa.s at 1000s-1 (thixotropic behaviour) thus making the ink suitable to coating or printing techniques. The sheet resistance of the films prepared by blade coating is down to 2.2 Ohm/sq for 25 ?m thickness. One particular application enabled is flexible
passive radio-frequency identification (RFID) antennas which can have a read range of >10 m (865-868 MHz) which is comparable with printed copper or silver RFID tags [6]. Graphene, however, is more stable than copper, which is prone to oxidation [7], and cheaper than silver [7].

[1] A. C. Ferrari et al. Nanoscale 7, 4598 (2015)
[2] F. Bonaccorso et. al. Nature Phot. 4, 611 (2010)
[3] F. Bonaccorso et. al. Science 347, 1246501 (2015)
[4] K. R. Paton et al. Nature Materials 13, 624 (2014)
[5] Karagiannidis et al. ACS Nano 11, 2742 (2017)
[6] K. Koski et al. Int J Adv Manuf Technol 62, 167 (2012)
[7] S. Magdassi et al. Materials 3, 4626 (2010)