Ceramic Fibres with Controlled Micro- and Macrostructures by Sol-Gel Electrospinning

Electrospinning is a well-developed technique for fabricating one-dimensional (1D) fibres in the form of two-dimensional (2D) nonwoven mats. In junction with sol-gel synthesis, single and multiphase ceramic fibres made of oxides and nitrides have been produced. Such ceramic fibre mats, with a unique combination of large surface area, high porosity, flexibility, show great premises for advanced applications such as flexible electronics and sensors. However, the ability to tune the morphology, porosity and the macroscopic shape of fibre product is still limited. For example, it is challenging to produce highly porous three-dimensional (3D) fibre architectures which are desired in tissue engineering, air filtration, absorbent, etc. Thus, developing strategies to control the micro- and macrostructures of ceramic fibres is the key to facilitate their practical implementation and broaden potential usages. <br/> <br/>Here, we report several solution modification strategies to effectively tune the structure of electrospun fibres, allowing customised fibre porosity and surface area. At the microscopic level, inducing liquid-liquid phase separation in spinning solution leads to core-shell fibre structures without the need of employing a complex spinneret. The pores size and shape can be controlled by varying the ratio of alkoxides, solvent, and polymer component. Also, electrospin the solutions with homogeneously dispersed submicron-sized polymer powders gives hybrid fibres. Such powders act as pore-forming templates to render mesopores and macropores inside fibre after calcination. At the macroscopic level, modifying the electrical conductivity of the spinning solution triggers different electrodynamic behaviour of electrified solution jet. The as-spun fibres spontaneously assemble into sponge-like macrostructure with centimetre-scale height, which is in sharp contrast to the conventional electrospun thin nonwovens. After calcination, the resultant ceramic fibre sponges show extremely high porosity (about 99.9%), high specific surface area (up to128 m2/g), excellent flexibility and elasticity. Overall, we introduce novel solution modification strategies towards a new class of electrospun ceramic fibres with unprecedentedly controlled micro- and macrostructures.