The flexible field emission cathode materials, with the unique advancements of deformability and bendability, have wide potential applications in the fields of electronic textiles, distributed sensors, paper displays and the large bending displays on building surface. Thus, the investigation on the flexible device systems, based on the semiconductor nanostructures with both high flexibility and excellent performance, becomes one of the hot research topics currently. In the present review, we firstly provide a brief introduction to the major features of the flexible field emission cathode materials. Then we make a comprehensive review on the research progresses focused on the fabrications of the flexible field emission cathode materials grown on the typical substrates of polymers, graphenes and carbon fabrics. Subsequently, we shed some lights on the potential applications of the flexible cathodes in the field emission displays and X-ray tubes. Finally, the future development directions of the flexible field emission cathode materials are prospected.

Contents
1 Introduction
2 The characteristics of flexible field emission cathode
2.1 Bendability
2.2 Ductility
3 Preparation and properties of flexible field emission cathode materials
3.1 Flexible polymer
3.2 Graphene
3.3 Carbon cloth
4 The applications of flexible cathode
4.1 Field emission display
4.2 X-ray tube
5 Conclusion and outlook