| Flexible electronics have attracted extensive attention due to their unique advantages of flexible,efficient,and low-cost manufacturing processes.The increasing demand of flexible electronics poses a growing environmental problem due to the wide use of plastics as the substrates,which would make a destruction to the environment we cherished.In order to fit the current era of sustainable development,researchers began to look for"green"substrates instead of existing plastics to make environmentally friendly flexible electronic devices.Compared with the plastic counterpart,paper is low-cost(1/20 price compared with that of polyethylene terephthalate),renewable,sustainable,biodegradable,and their enormous potential for large-scale production,allowing for a rapid development of paper-based flexible electronics.Furthermore,paper-based conductive materials have attracted a great deal of attention of scientific researchers.How to prepare paper-based conductive materials that meet the requirements of flexible products and make it become the indispensable part of it,and which were based on the structural characteristics of paper and another“green”materials.This idea will have a great significance for expanding the application of paper-based conductive materials in the field of flexible electronic devices.Therefore,the experimental part of my paper was divided into three parts,and the application of cellulose paper in flexible electronic devices was explored step by step.The first part:by dehydrating the suspension of natural cellulose fibers derived from eucalyptus into traditional paper,the concept of using a conductor with a high Young's modulus,such as gold,silver,copper and other metals,to prepare conductive paper will lead to material delamination and/or local fracturing when bending the composite paper.Thus,a new strategy to fabricate bendable conductive paper with simultaneous mechanical and electronic robustness is a prerequisite.Herein we demonstrated a low-cost(?1.3 dollars/m~2),reliable,and long-term(stable for more than two months)ionic gel paper(IGP).Ionic gels contributed two significant advantages:(1)A lower Young's modulus compared with that of cellulose fibers and facile manufacturing.(2)As a result,IGP show a high electrical durability with negligible bending-recovering signal changes over 5000 cycles.What's more,the as-prepared conductive paper was used for electroluminescent devices.Our methodology has the potential to open up a new powerful route to fabricate bendable conductive paper for a myriad of applications in future flexible.The second part:in spite of achieving long-term stable ionic gel conductive paper,two issues exist preventing its practical manufacture.One is the inconvenient heating process to release extra volatile organic compounds(VOCs)to the atmosphere,indicating a waste of fabrication time and a potential harm to the environment.The other is the poor patternability to generate paper circuits due to the fluidity of ionic gels.Therefore,it is urgent to find a substrate that is more environment-friendly and more printable to expand the application range of conductive paper.Herein we report a facile fabrication of conductive paper based on in situ polymerization of polymerizable deep eutectic solvents(PDESs)through a screen printing process.The PDES was used as the ink to print upon the base paper through the pre-designed screen,and they cured into conductive elastomers under UV irradiation within30 seconds,since the PDESs play‘‘all-in-one''roles,including reactant medium,precursor and conductive fillers,in their polymerization,the inconvenient heating process is not required.In a addition,the whole preparation process is rapid(<30 seconds),green and VOC-free.The as-prepared conductive paper shows stable electrical&mechanical robustness.Using these paper circuits as key components,we built a variety of proof-of principle demonstrations to show its capacity in constructing origami paper circuits.By pre-designed circuit paths and careful integration,on-demand input/output 3D circuits can be achieved,showing its flexibility to origami electronics.This strategy of PDES based conductive paper,as well as origami circuits,may be applied to other conductive components for flexible electronics.The third part:for the long-term stable ionic gel conductive paper and the type of PDES conductive paper,we found that the transparency of the paper-based conductive material prepared was not high enough,limiting the special application of conductive paper in flexible electronic devices.The conventional nanofiber paper was hard and brittle due to a high Young's modulus.Therefore,we propose a method to ameliorate this deficiency,the as-prepared conductive film was immersed into the choline chloride/urea aqueous solution with a plasticizing function.Owing to the hydrogen bonding between the molecules,the final conductive paper exhibits a soft and stretchable"elastic"behavior,which has increased about tenfold in tensile properties.The fabricated conductive paper has some advantages of high visual appearance(~90%)and stretchable(17%),and it could be used as a paper-based capacitor.To some extent,this mean plays a considerable role in extending the influence of paper-based conductive materials in the application of flexible electronic devices. |
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