Studies On The Formation Of Graphene Micro-scale Structures Using Electrohydrodynamic Atomization Deposition And Electrohydrodynamic Jet-printing

Graphene has attracted intense attention due to its unique structures and properties and potential applications in the fields of electronics and sensor such as biosensor, supercapacitor, field-effect transistor, composite material etc. In order to adapt graphene into these applications, the formation of graphene films and pattern graphene structures is of great important. In the work, electrohydrodynamic atomization (EHDA) deposition and electrohydrodynamic jet (EHDJ) printing technique were employed in the process to rapid form different graphene films and structures which could achieve controllable manufacturing.Both nafion and ethyl cellulose dispersants were used to prepare graphene suspension, which were suitable for EHDA deposition and EHDJ printing. Highly dispersive graphene nano-particles were deposited by EHDA. Graphene particles and films were deposited, and the influence of atomization-substrate distance on the characteristics of the graphene films and their sheet resistance were analysed. A distance of3mm was found to be the optimum deposition distance for this graphene suspension to produce even film and low sheet resistance. The lowest sheet resistance was40Ω sq-1(ohms per square) using graphene/ethyl cellulose suspension. Raman spectra of the graphene films using EHDA deposition technique at the working distance of3mm contained the main hallmarks of graphene which had reported in the literature. Contact angle of graphene films were analysed, and all the deposited films showed obvious hydrophobic properties, which could be implemented hydrophobic modification on the surface of silicon.EHDA deposition combined with metal and photoresist micro-moulds were used to form graphene structures and micrographics, respectively on PDMS substrate and the glass substrate using two kinds of graphene suspension. The influences of different micro-moulds on graphene micro-scale structures were analyzed. When the metal moulds widths were smaller than60μm, the density of structures decreased, and for the photoresist micro-moulds, when the widths were smaller than30μm, the density of structures decreased. Combined MEMS technology with EHDA deposition, modified electrode was made by depositing graphene particles on the platinum electrode surface. The modified electrode was assembled into a microfluidic chip and the electrochemical detection results showed that after modifying graphene, the platinum electrodes had better electrochemical sensitivity.The influences of different printing height and flow rate on electrohydrodynamic jets were studied. Analysis found that printing height and flow rate directly changed the geometrical and electrical parameters of microstructure. With a nozzle inner diameter of0.3mm,65μm graphene lines and micro-scale structures were printed by EHDJ. Array graphene electrodes were printed with150um width, and its conductivity were1.83×104S/m. The electrodes showed high sensitivity after detecting the lead ion in the solution by using stripping voltammetry.