Graphene is a much-discussed material across industries, and the textile sector is no exception. It is not only the strongest material ever tested, but it also conducts heat and electricity efficiently, and is nearly transparent. Its highly conductive nature has naturally led to research into its use in e-textiles, and reduced graphene oxide (rGO), a slightly less conductive form of graphene, has already made its way into inks for textile printing.
Now, a new patent filed by the University of Manchester, UK, the birthplace of graphene, looks to add a new dimension to this conversation. According to the patent, the invention specified is an “electrically conductive material comprising: a porous substrate material; a hydrophobic surface coating covering at least a portion of a surface of the porous substrate material; and an electrically conductive track or film disposed on the hydrophobic surface coating.”
The electrically conductive track or film is said to comprise graphene and/or rGO. Crucially, the process for forming the electrically conductive material is said to include “digitally printing (eg inkjet printing) a hydrophobic surface coating formulation onto at least a portion of a surface of the porous substrate material to form a hydrophobic surface on the substrate.”
Inkjet printing of textile coatings has been an area of development for the industry that has not yet seen full commercial use. This is mainly due to the viscosity of the coatings and the fragility of print head technology. However, the patent states that “the particles of hydrophobic polymeric material present in the formulation have an average size of less than 450 nm,” making them suitable for use with inkjet technology.
Not only is the coating to be inkjet printed but the electrically conductive formulation that includes graphene will also be printed in this way. The patent explains that one to ten layers of graphene or rGO are required to be deposited onto the coated substrate to achieve conductivity, adding: “Typically, the length and width of the layers are within the range of 10 nm to 2 microns. The flakes are deposited by digitally printing (eg inkjet printing) an electrically conductive ink formulation that comprises flakes of graphene or graphene oxide.”
The technology used for digital printing of both the coating and the ink is described as a standard inkjet technology and the patent even notes that, “the specific method by which the inkjet ink is deposited onto the substrate surface varies from system to system, and includes, amongst others, continuous ink deposition and drop-on-demand ink deposition.”
It also references ‘other digital deposition’ techniques including Cambridge, UK-based Alchemie Technology’s Jetronica system. The patent continues: “The use of digitally printing has a number of advantages over conventional fabrication processes. In particular, digitally printed conductive patterns are typically: faster to produce than subtractive processes (such as etching) or complex weaving processes; less wasteful; less hazardous (ie use less hazardous chemicals); less expensive than conventional techniques; compatible with a wide range of substrates; simple to implement; and enable the possibility of further post-fabrication processing.”
