From Short Electrospun Nanofibers to Ultralight Aerogels with Tunable Pore Structure

Abstract

Nanofiber production by electrospinning has made great progress over the past two decades. Recently the research area was revolutionized by a novel post-processing approach. By cutting the endless and intertwined nanofibers into short pieces, it is now possible to reassemble them into interconnected 3D structures. Such highly porous structures are built from dispersed short nanofibers by freeze-casting. This solid templating process controls the structures' ultimate properties and architecture in terms of primary and secondary pores below 5 µm and between 10 and 300 µm, respectively. The objective of this review is to provide insight into this young field of research, in particular highlighting the processing steps, materials and current applications, from scaffolds for tissue engineering, acoustics, sensors and catalyst supports to filtration.

Cellulose Silica Hybrid Nanofiber Aerogels: From Sol–Gel Electrospun Nanofibers to Multifunctional Aerogels

“…In order to strengthen the network, we thermally treated CDA‐only and as‐prepared hybrid NFA. Although most of the previously conducted research involves chemical crosslinkers to strengthen the structure of conventional aerogels or NFA, our rationale to use thermal treatment was to maintain the sustainable nature of the process and also enhance possibilities of interactions between sol–gel processed silica and CDA network in a simple way. Upon thermal treatment, hybrid‐NFA display remarkable retention in their 3D (Figure E) structure with about 4.1% rise in density and 0.3% loss in porosity (Table S1, Supporting Information), while CDA‐NFA completely collapse in structure generating a solid mass with complete loss in 3D orientation (Figure F).…”

“…In this regard, a recent approach to fabricate 3D nanofiber aerogels (NFA) from electrospun nanofiber by marrying the art of electrospinning with aerogel production has gained strong momentum, and researchers have fabricated nanofiber based aerogels (NFA) using precursors such as polyvinyl alcohol (PVA), polyacrylonitrile (PAN), and various forms of cellulose . The solid templating process in this methodology involves freeze casting followed by freeze drying a suspension of short electrospun nanofibers in a nonsolvent to generate ultralight, self‐supportive aerogels .…”

Dye Adsorption and Electrical Property of Oxide-Loaded Carbon Fiber Made by Electrospinning and Hydrothermal Treatment

“…The three-dimensional (3D) nanofiber aerogels were made from dispersing short nanofibers in a 1,4-dioxane solvent followed by unidirectional freezing and sublimation of the solvent [29]. The ultralight aerogels with tunable pore structures [30] and 3D nanofiber/nets [31] were faster than the flat nanofiber membranes in dye removal because of they possess the required hierarchical porous structures, allowing them to be suitable for making deep-bed filters.…”

Nanofiber-based Aerogels

“…Possible applications include filtration, thermal insulation, support for catalysts, or scaffolds for tissue engineering. [3] Mostly, synthetic polymers such as PAN and PVA have been used as fiber materials or their blends with biopolymers such as pullulan and gelatin. [3] The synthesis of the aerogels starting from electrospun nanofibers is straight forward and includes a freeze drying step followed by a process to stabilize the porous structure, such as chemical or thermal cross linking.…”

“…[3] Mostly, synthetic polymers such as PAN and PVA have been used as fiber materials or their blends with biopolymers such as pullulan and gelatin. [3] The synthesis of the aerogels starting from electrospun nanofibers is straight forward and includes a freeze drying step followed by a process to stabilize the porous structure, such as chemical or thermal cross linking. The freeze drying step is also crucial for the pore structure of the aerogel and can be exploited to tailor size and structure of minor and major pores.…”