Significance Colloidal electrospinning is a new micro-nano preparation technology based on electrospinning. The colloidal particles are mixed with the template polymer solution and electrospun, and the colloidal particles are embedded in the nanofibers. On the one hand, the template polymer improves the spinnability of colloidal particles and provides a flexible carrier for colloidal particles and on the other hand the embedding of functional colloidal particles brings new functions to the fiber. In order to further understand the morphology control for wide applications of colloidal electrospinning fibers, this paper reviews the concept, working principle, morphology shape influencing factors, spinning treatment and application of colloidal electrospinning, and the future development of colloidal electrospinning prospect. Progress As a branch of electrospinning, colloidal electrospinning makes it possible that composite micro/ nano fiber membranes with special structure and properties can be obtained by electrospinning after mixing colloidal particles with template polymer. Colloidal particles can be divided into three categories, i.e. inorganic colloidal particles such as silicon dioxide (Si02) , polymer colloidal particles such as polystyrene (PS) and poly ( methyl methacrylate) ( PMMA ) and temperature-sensitive microgel particles such as poly ( N-isopropylacrylamide ) (PNIPAm), Poly ( N-vinylcaprolactam) (PVCL). Template polymers can improve the spinnability of colloidal particles and provide flexible carriers for colloidal particles among which poly (vinyl alcohol) (PVA) is the most commonly used template. The morphology of colloidal electrospun fiber mainly depends on the ratio of colloidal particles to template polymer, colloidal particle size, surfactant, viscosity of spinning solution and spinning voltage, and so on. It has been reported that there are beaded structure, bracelet structure, one-dimensional colloidal assembly, necklace structure, colloidal rod structure, spindle-like structure, colloidal fiber structure, and black berry-like structure. The range of application can be further broadened by different treatments before and after colloidal electrospinning. On the one hand, colloidal particles can be used as a nano-container to load drugs or metal oxide particles, and on the other hand, the composite fibers can be calcined, soaked and cross-linked, which can give the fibers new functions. The fiber membranes with different treatments can be used in the fields of super hydrophobicity, adsorption, catalysis, sensing, tissue engineering, photonic crystal fiber and so on. Conclusion and Prospect At present, composite micro/nano fiber membranes with various morphologies and functions can be prepared by colloidal electrospinning and further treatment, but the research on colloidal electrospinning is still in its infancy. The preparation of composite fiber membranes with flexibility, good mechanical properties and specific function by colloid electrospinning demands further research. In order to better develop of colloidal electrospun fiber, the future research can be carried out from the following four aspects. (T)At present, colloidal electrospinning is mainly univariate colloidal electrospinning. In the future, multicomponent colloid electrospinning technology should be developed to integrate multiple functions on the fiber membrane, or to realize the controlled release of many drugs on the fiber membrane. ©After the template polymer in the composite fiber membrane is removed by calcination or immersion, the fiber membrane has higher brittleness and poor mechanical properties, which limits the further application of the fiber membrane. In the future, the mechanical properties can be enhanced by improving the interaction between colloidal particles, such as physical or chemical interaction.
