# Electrospinning of High-Performance Nanofibres: State of the Art and Insights into the Path Forward
## 1 Introduction  
High-performance fibres show enhanced properties compared to conventional fibres including excellent mechanical properties, flame resistance, thermal resistance, and chemical resistance [1]. As demands for stronger, safer, lighter, and faster textiles increase, so too do the demands for high-performance fibres. Today, these fibres are employed for a variety of applications including aerospace, biomedical, construction, protective clothing, geotechnical, and electronics. High-performance polymers can also be used to produce nanofibres, allowing the polymers' properties to be combined with the benefits of nanoscale materials including light weight, high surface area to volume ratio, and morphology variation to achieve unique material properties [2]. Nanofibres are one-dimensional nanomaterials with diameters in the nanoscale [3]. Nanofibrous membranes have been used in a wide variety of applications including biomedical and tissue engineering, energy storage, electronics, filtration, and protective clothing [2, 4]. The use of high-performance polymers to produce nanofibres provides a means to improve the mechanical, thermal, and chemical properties of the nanofibrous membranes [3].  
A variety of methods can be used to produce nanofibres [4]. Bottom-up methods rely on a high degree of precision but can create unique and hyper-specific morphologies by combining polymeric building blocks. Top-down methods require less precision, thus limiting their customizability, but allow for the continuous production of a nanofibrous web. This is advantageous for industrial scale-up, as nanofibres can be more readilymass-produced using top-down methods. The most popular method of production for nanofibres is electrospinninginning. In electrospinningning, high voltage in the kV range is used to form a liquid jet from a polymer melt or solution. This jet becomes solidified as the melt is frozen or the polymer solution is evaporated and is then deposited on a collector, creating a nanofibrous membrane structure. The process is highly adaptable, and a wide variety of materials including polymers, metals, and ceramics can be used to produce nanofibres via electrospinningning. Fibre morphologies may be adapted to create porous fibres [5], helical fibres [6], and composite fibres [7]. The collectors can be varied to alter the resultant fibre output, producing randomly oriented membranes, highly aligned membranes, uniquely designed structures, and nanofibrous yarns [4]. Electrospinning is a scalable, repeatable, convenient process with great versatility to produce a number of fibre morphologies, which makes it the most popular nanofibre production method today [2].  
For high-performance polymers, electrospinningning has been used to produce nanofibres from polymers including m-aramid [7; 8; 9; 10; 11; 12], p-aramid [3; 13; 14; 15], PAI [5; 16; 17; 18; 19; 20; 21], PBO [16; 22; 23; 24; 25], and PBI [26; 27; 28; 29; 30; 31; 32; 33]. Although some reviews have considered high-performance nanofibre fabrication for specific applications [34; 35], or a specific type of high-performance fibre [14; 36], no reviews so far have summarized the general progress in the electrospinningning of high-performance nanofibres. An enhanced understanding of the challenges and progress in fabrication techniques among high-performance fibres is a necessary step in working toward the wider adoption and mass production of high-performance fibres. Since electrospinningning currently provides the most scalable method for producing nanofibrous membranes, this method of nanofabrication will be the focus of the review. The progress and challenges in the electrospinningning of high-performance fibres will be discussed here to provide a summary of the field and determine the critical next steps in the advancement of electrospun high-performance fibres.