The effect of plasma functionalization on the print performance and time stability of graphite nanoplatelet electrically conducting inks

Andrew Claypole,James Claypole,Tim Claypole,David Gethin,Liam Kilduff

doi:10.1007/s11998-020-00414-4

Andrew Claypole, James Claypole + Show 3 more

Open Access

https://doi.org/10.1007/s11998-020-00414-4

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Abstract

Carbon-based pastes and inks are used extensively in a wide range of printed electronics because of their widespread availability, electrical conductivity and low cost. Overcoming the inherent tendency of the nano-carbon to agglomerate to form a stable dispersion is necessary if these inks are to be taken from the lab scale to industrial production. Plasma functionalization of graphite nanoplatelets (GNP) adds functional groups to their surface to improve their interaction with the polymer resin. This offers an attractive method to overcome these problems when creating next generation inks. Both dynamic and oscillatory rheology were used to evaluate the stability of inks made with different loadings of functionalized and unfunctionalized GNP in a thin resin, typical of a production ink. The rheology and the printability tests showed the same level of dispersion and electrical performance had been achieved with both functionalized and unfunctionalized GNPs. The unfunctionalized GNPs agglomerate to form larger, lower aspect particles, reducing interparticle interactions and particle–medium interactions. Over a 12-week period, the viscosity, shear thinning behavior and viscoelastic properties of the unfunctionalized GNP inks fell, with decreases in viscosity at 1.17 s−1 of 24, 30, 39% for the ϕ = 0.071, 0.098, 0.127 GNP suspensions, respectively. However, the rheological properties of the functionalized GNP suspensions remained stable as the GNPs interacted better with the polymer in the resin to create a steric barrier which prevented the GNPs from approaching close enough for van der Waals forces to be effective.

Highlights

Carbon-based pastes and inks are used extensively in a wide range of printed electronic devices, including resistive heater panels, electrochemical sensors, pressure sensors, printed batteries, and supercapacitors.[1]
This study aims to establish whether plasma functionalization provides an effective means of maintaining particle dispersion by comparing changes in time to the shear and complex rheology of suspensions of ammonia plasma functionalized graphite nanoplatelets (NH3 GNP) and unfunctionalized graphite nanoplatelet (R1 GNP), Materials and methods
The viscosity of the R1 GNP suspensions showed good fit to the model developed for NH3 GNP.[27]

Summary

Introduction

Carbon-based pastes and inks are used extensively in a wide range of printed electronic devices, including resistive heater panels, electrochemical sensors, pressure sensors, printed batteries, and supercapacitors.[1] Advantages of carbon inks include their relatively low cost, disposability, ease of use, chemical inertness, the ability to be modified or functionalized and their controllable electronic properties.[2,3,4,5] Dispersion of nano-fillers is a key issue in governing the properties of composites.[6,7] achieving good dispersion of nano-carbons within a fluid has proved difficult as a result of the inert, hydrophobic, ultra-high interfacial area per volume and highly agglomerated nature of carbon nanomaterials.[8,9,10,11] Atomic motions in neighboring particles drive carbon nanomaterials together and, if not counteracted, the van der Waals forces cause particles to adhere to each other upon contact.[12,13]. Acid treatments have been used with the aim of adding carboxyl and hydroxyl groups to

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