Unveiling the Mechanism of the in Situ Formation of 3D Fiber Macroassemblies with Controlled Properties

Abstract

Electrospinning technique is well-known for the generation of different fibers. While it is a "simple" technique, it lies in the fact that the fibers are typically produced in the form of densely packed two-dimensional (2D) mats with limited thickness, shape, and porosity. The highly demanded threedimensional (3D) fiber assemblies have been explored by timeconsuming postprocessing and/or complex setup modifications. Here, we use a classic electrospinning setup to directly produce 3D fiber macrostructures only by modulating the spinning solution. Increasing solution conductivity modifies electrodynamic jet behavior and fiber assembling process; both are observed in situ using a high-speed camera. More viscous solutions render thicker fibers that own enhanced mechanical stiffness as examined by finite element analysis. We reveal the correlation between the universal solution parameters and the dimensionality of fiber assemblies, thereof, enlightening the design of more "3D spinnable" solutions that are compatible with any commercial electrospinning equipment. After a calcination step, ultralightweight ceramic fiber assemblies are generated. These inexpensive materials can clean up exceptionally large fractions of oil spillages and provide high-performance thermal insulation. This work would drive the development and scale-up production of next-generation 3D fiber materials for engineering, biomedical, and environmental applications.

3D Electrospinning of Al2O3/ZrO2 Fibrous Aerogels for Multipurpose Thermal Insulation

“…The ber assemblies were categorized into three types, (b1) cloud-like ber piles consisting of micro bers and solution droplets visible to the naked eye, (b2) thin mats of densely packed sub-micron bers, and (b3) centimeter-high self-supporting 3D assemblies which were used for further studies due to the ultrahigh porosity, uniform ber morphology, and interweaved continuous ber network. The signi cant differences between the ber macrostructures are attributed to (i) the different electrodynamic behavior of solution jet, which is affected by the solution electrical conductivity, and (ii) the mechanical properties of single bers [27]. Only when the bers are stiff enough to resist gravity can they support a free-standing 3D structure, which requires a solution with moderate viscosity.…”

“…The tortuosity of the ber network was evaluated using an open-source Matlab app, TauFactor [67]. The input microstructural data was taken from our previous work, which was the 3D-reconstructed tomography of an electrospun 3D ber macro-assembly with density of 3.6 mg cm -3 [27]. Although our previous ber assembly was made of different ceramic materials, the structure of the ber network shows a great resemblance to the AZFA in this work.…”

“…Fortunately, recent studies show that only by modifying the spinning solution, ultralight three-dimensional (3D) ber sponges can be generated without the need for any post-treatment or specialist equipment beyond the standard electrospinning setup [27,28]. Calcination of such electrospun bers directly creates CFAs that consist of ultralong bers entangled into a continuous 3D network.…”

Free‐Boundary Microfluidic Platform for Advanced Materials Manufacturing and Applications

“…[258] Nowadays, such three-dimensional electrospun products are considered to have broader application prospects because of their freer designability and more diverse porosity, structure, and function. [257,265] Near-Field Electrospinning/Electrowriting: Although various electrospun micro-nano fibers and fibrous products can be obtained by improving or modifying the nozzle, ink composition, collecting method, or collector as well as by applying supplementary forces (e.g., airflow) or installing auxiliary devices, they can hardly solve the problem that traditional far-field electrospinning cannot realize precise fabrication of patterned microstructures due to chaotic deposition of nanofibers. In contrast, near-field electrospinning is proposed to precisely manipulate the position of its jetting product deposited to enable patterned micro-nano additive manufacturing, [250,271,277] which shares a similar goal and system configuration to EHD inkjet printing.…”

Driving Fiber Diameters to the Limit: Nanoparticle-induced Diameter Reductions in Electrospun Photoactive Composite Nanofibers for Organic Photovoltaics

“…The spinning solutions of conjugated polymers are typically non-conductive, and the solvent, often chloroform, possesses a low dielectric constant of 4.81. Therefore, co-solvent addition delivered a diameter reduction attributed to an increase in solution conductivity up to 0.35 µS cm -1 , [19] which likely allowed the rst onset of bending instability during spinning to occur closer to the needle [29,30]. This approach was used to electrospin sub-100 nm P3HT nano bers (80 nm), and the rst instance of a photoactive nano ber, in this case, poly[N-9'-hepta-decanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT), with a diameter approximately twice that of the exciton diffusion length of the material, at 20 nm [16].…”