Environmentally Friendly Graphene Inks for Touch Screen Sensors |
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Authors: | Sergey Tkachev Miguel Monteiro João Santos Ernesto Placidi Mohamed Ben Hassine Pedro Marques Paulo Ferreira Pedro Alpuim Andrea Capasso |
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Affiliation: | 1. International Iberian Nanotechnology Laboratory (INL), Braga, 4715-330 Portugal;2. Dipartimento di Fisica, Università di Roma La Sapienza, Roma, 00185 Italy;3. Displax S.A., Rua Soldado Manuel Pinheiro Magalhães, 68, Braga, 4715-167 Portugal;4. International Iberian Nanotechnology Laboratory (INL), Braga, 4715-330 Portugal
Mechanical Engineering Department and IDMEC, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, Lisbo, 1049-001 Portugal
Materials Science and Engineering Program, The University of Texas at Austin, Austin, TX, 78712 USA |
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Abstract: | Graphene-based materials have attracted significant attention in many technological fields, but scaling up graphene-based technologies still faces substantial challenges. High-throughput top-down methods generally require hazardous, toxic, and high-boiling-point solvents. Here, an efficient and inexpensive strategy is proposed to produce graphene dispersions by liquid-phase exfoliation (LPE) through a combination of shear-mixing (SM) and tip sonication (TS) techniques, yielding highly concentrated graphene inks compatible with spray coating. The quality of graphene flakes (e.g., lateral size and thickness) and their concentration in the dispersions are compared using different spectroscopic and microscopy techniques. Several approaches (individual SM and TS, and their combination) are tested in three solvents (N-methyl-2-pyrrolidone, dimethylformamide, and cyrene). Interestingly, the combination of SM and TS in cyrene yields high-quality graphene dispersions, overcoming the environmental issues linked to the other two solvents. Starting from the cyrene dispersion, a graphene-based ink is prepared to spray-coat flexible electrodes and assemble a touch screen prototype. The electrodes feature a low sheet resistance (290 Ω □−1) and high optical transmittance (78%), which provide the prototype with a high signal-to-noise ratio (14 dB) and multi-touch functionality (up to four simultaneous touches). These results illustrate a potential pathway toward the integration of LPE-graphene in commercial flexible electronics. |
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Keywords: | 2D materials flexible electronics liquid-phase exfoliation transparent conductive electrodes transparent conductive oxides |
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