# Electrospun Nanofibers for Integrated Sensing, Storage, and Computing Applications
## 2 Different Types of Electrospun Nanofiber Process and Structures
### Parameters Affecting Electrospinning  
Electrospinning gives the corresponding nanofibers many advantages over conventional film-based planar materials, such as better mechanical characteristics, more flexibility, better uniformity, enhanced electrical properties, more porosity, larger surface area, and ease of synthesis and processing. Nevertheless, its large-scale commercial production still has a long way to go. This sophisticated method involves many technological procedures and appropriate control over the whole electrospinning process is necessary to promote efficiency and fiber performance. The features of electrospun nanofibers are dependent on several parameters falling into three main categories: inner properties of the solution, conditions of the electrospinning process, and surrounding environmental factors. Firstly, solution variables generally contain the molecular weight, viscosity, polarity, concentration, surface tension, electrical conductivity, and elasticity of the solvent. Among them, concentration is a typical factor affecting the morphology and characteristics of the electrospun nanofibers. To form the continuous fibers, a critical concentration should be reached for the occurrence of the electrospinning process. At low concentration, the diameter of nanofibers is smaller on average [53] and what is even worse is the formation of droplets and beaded nanofibers caused by insufficient chain entanglement to stabilize the surface tension of the jet. However, a much higher concentration could also harm the construction of fibers due to the relatively higher viscosity of the solution [54]. Consequently, proper concentration is the key to the formation of uniform and smooth nanofibrous materials, letting the electric field fully override the surface tension. The viscosity and surface tension of the solution impact the electrospinning process and fiber fabrication in the same manner as the concentration: In the solution with too high or low viscosity and surface tension, the formation of fibers will be limited. Thus, suitable parameters are crucial for the production of high-quality fibers. Particularly, the electrospinning process would be applied at lower applied voltages when lower surface tension is achieved [55]. Furthermore, the molecular weight of the targeted material in the electrospun solution plays a critical role in the formation of good nanofibers. With a lower molecular weight, a relatively increased diameter of the fibers appears [10]. Opposite to the anti-dependence of the molecular weight and fiber diameter, increased electrical conductivity of the solution would lead to increased fiber diameter, but a slight decrease would occur later [56]. Conditions of electrospinning process, such as applied voltage, feed rate of the solution, and the distance between the spinneret and the collector, are other influencing factors that belong to the following part to achieve tunable fiber morphology and quality after getting the electrospun solution ready. Particularly, electrospinning variables have a significant connection with the diameter of the fibers. For example, a smaller size of fibers will be collected on the plate with a small inner diameter of the spinneret as a result of the increased surface tension of the charged jet [57]. Then, the acceleration of the jet will be weakened for the need for more energy to overcome the interfacial tension, and more time for the jet to be stretched into a smaller diameter is needed. Besides, a growing flow rate and smaller distance between the needle and the collector will bring increased fiber diameter despite the extreme circumstances [58]. Environmental factors, including ambient humidity and temperature, influence the quality of the jet and its deposited fibers at any time. Studies have reported that high humidity will cause shorter solidification time and in such cases prolong the produced jet, whereas low humidity will lead to too thorough evaporation of the solvents, and the formation of the continuous fibers would be impeded [59].