Electrospinning is a technique used to fabricate polymer fibers in micro- and nanoscales. Due to the large distance between the nozzle and collector, there is a limited positioning accuracy of electrospun fibers. To enhance the possibility of fabricating structures with micrometer placement, an electroprinting technique has been developed. By reducing the distance between the nozzle and the collector it is demonstrated that it is possible to get an improved control over fiber positioning which gives a possibility to fabricate designed 3D structures at the micron scale. In this study, cellulose acetate (CA) has been selected as a biomaterial to advance the 3D printing of membranes with possible use in separation applications. Various parameters, such as CA concentration and molecular weight, printing speed, printing pattern, applied voltage, etc. are evaluated with respect to printing control. Results indicate that by optimizing the printing parameters it is possible to print structures with inter- fiber distances down to 3 mu m and fiber diameters at a sub-mu m scale. This electroprinting development is promising for the fabrication of customized separation membranes. However, printing speed still remains a challenge.

3D printing is envisioned to play an important role in the production of membranes for e.g., water purification and bio-separation applications due to the prospect of creating new and cleverly designed structures. Among different 3D printing techniques, direct ink writing offers the opportunity to print a wide variety of materials with high-detail resolution. There is a range of parameters that need to be optimized in order to develop robust printing techniques at that scale. In this study, cellulose acetate (CA), which is a biocompatible material, has been used as an ink. In order to examine the printability and the possibility of printing features as small as a few mu m, nozzles with different diameters and inks with varying amounts and molecular weights of CA were investigated. Findings in this study indicate that, depending on the wetting on the underlaying structure, the nozzle's internal and external diameter affects the detail resolution of the printed structure. Different inks result in different widths of printed strands and generally a higher amount and higher molecular weights of CA results in higher detail resolution. However, too high amount of CA and molecular weight will increase the clogging risk in the nozzle. In this study, the internal size of the nozzle was 3 mu m, and by selecting a suitable ink, it was possible to print strands down to 1 mu m size and 6 mu m inter-strand distance in the air, bridging supports with limited sagging. Furthermore, wall structures consisting of 300 layers, corresponding to about 300 mu m in total height, were successfully printed.

This study focuses on the fabrication and analysis of 3D-printed high detail resolution cellulose acetate (CA) structures, particularly examining their specific surface area per volume. While electrospinning is a widely used technique for creating nanofiber membranes with high, which is advantageous for applications like chromatography, the performance could be further improved by precisely controlling fiber placement. To further develop membranes, this research explores the use of electroprinting with small distances between nozzle and collector, here named near-collector electroprinting, to create 3D structures. By optimizing printing parameters, in particular the reduction of the nozzle-to-collector distance, 3D structures with precise fiber placement within a few micrometers were fabricated. The specific surface area per volume was calculated for both 3D-printed and electrospun filters. Results showed that 3D-printed structures with a 5 µm pitch achieved anper volume similar to electrospun filters. Incorporating polyethyleneimine (PEI) in the CA ink enabled the 3D-printed structures to gain ion binding capacity which was further investigated. This ion-exchange ability which integrated into the printing step, eliminating the need for a separate post-modification process in bio-separation applications. By switching the substrate voltage from positive to negative, relative to the grounded nozzle, the printed fiber diameter decreased substantially for the CA ink with PEI. The    for fibers of this material could therefore potentially be higher than that of electrospun membranes, provided that the fiber placement control can be maintained at an order of magnitude higher printing speed than presently possible. These findings suggest that near-collector electroprinted CA structures offer potential improvements in membrane design and performance, making them a promising alternative to traditional electrospun membranes for bio-separation applications.

The fabrication of scaffolds that replicate the structural complexity of native tissues is essential for advancing tissue engineering. This study explores near-collector electroprinting, a 3D printing technique to create structured scaffolds with controlled spacing of µm fibers down to 5 µm pitch. Human mesenchymal stromal cells (hMSCs) cultured on electroprinted cellulose acetate (CA) scaffolds exhibited high viability, and fiber spacing playing a crucial role in regulating cell adhesion, alignment, and bridging behavior. Scaffolds with many-layer and small pitches (20 µm) facilitated enhanced cellular connectivity, while larger pitches led to more random distribution. Also, lignin, a naturally occurring biopolymer with antibacterial and antioxidant properties, was incorporated into the scaffold to demonstrate the possibility of printing composite materials and evaluating its antimicrobial potential. The preliminary results indicate that CA-lignosolfunate (derivative of lignin) scaffolds reduce bacterial colony formation. These findings establish near-collector electroprinting as a scalable and versatile method for potential applications in wound healing and infection-resistant biomaterials.