With the advances in knowledge and techniques, the regenerative medicine field moves towards more complex scaffold structures. The desire to comply with mechanical demands and mimicking the tissue to be replaced, requires more complex and spatially ordered scaffold structures. With electrospinning, creating submicrometer sized fibers tends to go at the cost of an ordered build-up and a controlled, positioned deposition of the fiber. Said that, maintaining a stable electrospinning jet allows you to electrospin complex ordered structures at a much lower length scale than most additive manufacturing techniques. There are different techniques, from solution as well as out of melt, to maintain a stable jet during electrospinning, sometimes also referred as electrohydrodynamic printing.
The resulting meshes can possess the structure of the 3D printed scaffolds, but with fibers diameter in the lower micro- to submicrometer range. In comparison, 3D printed scaffolds feature a fiber diameter range in the tens to hundreds of micrometers. Hence electrospun scaffold mimic extracellular matrix much closer and tend to be mechanical less rigid then its 3D printer counterparts.
Such 3D electrospun structures can for example be used to study the development of tumors in vitro, replacing the less-reliable 2D studies which are nowadays performed10. Additionally the use of electrospun written scaffold is investigated in the tissue engineering field to regenerate or replace tissue exhibiting ordered structures.
Since it enables to a highly precise fiber deposition and a high control of fiber morphology, electrospun written scaffolds find applications also in the field of photonic and sensing3.
In the attempt of generating controlled nanofibers deposition for e.g. structured scaffolds, near field electrospinning emerged as a technique. This technique could be simplified explained as a downsized electrospinning. It uses thinner nozzles, a very short spinning distance (500 µm to 1 mm) and a low voltage (200 V – 1.5 kV)1,2. Tuned properly this technique maintains a stable jet, allowing to build up a scaffold similar to fuse deposition modeling.
Electrospinning form a very high viscous solution is another technique to maintain a stable jet over the 10 to 20 cm distances used in conventional electrospinning. Suppressing the jet instability will always lead to general thicker fibers. When using this technique, the collected fibers will exhibit a fiber diameter in the micrometer range, while NFE also allows diameter in the submicrometer range.
A variant of melt electrospinning which has gain a lot of interest in the last years is a combination of the near field electrospinning and melt electrospinning. Melt electrospin writing possesses the ability to reach the nanometer fiber diameter in combination with a precise control of their deposition and the resulting pore size.
Melt electrospinning can be defined as an hybrid between fused deposition modeling and electrospinning. The fibers are formed as a result of the applied voltage and the resulting scaffold possesses the ordered structure of a 3D printed mesh5–9.