3D Printing for Soft Tissue Regeneration and Applications in Medicine

Abstract

The use of additive manufacturing (AM) technologies is a relatively young research area in modern medicine. This technology offers a fast and effective way of producing implants, tissues, or entire organs individually adapted to the needs of a patient. Today, a large number of different 3D printing technologies with individual application areas are available. This review is intended to provide a general overview of these various printing technologies and their function for medical use. For this purpose, the design and functionality of the different applications are presented and their individual strengths and weaknesses are explained. Where possible, previous studies using the respective technologies in the field of tissue engineering are briefly summarized.

Keywords: 3D bioprinting; additive manufacturing; regenerative medicine; soft tissue; tissue engineering.

Figure 1

Working stages in 3D printing.

Figure 2

Overview of the various 3D printing applications, based on the subdivision of ISO 17296-2.

Figure 3

Schematic representation of stereolithography (SLA) and digital light processing (DPL) as top-down approaches. Both processes are based on crosslinking a photosensitive resin using a laser. SLA cures the individual points of a resin layer one after the other. Digital light processing can cure entire layers at once, using so-called digital micromirror devices.

Figure 4

Schematic representation of the extrusion-based printing technologies. All applications have in common the use of a force directed at the nozzle to eject the material.

Figure 5

Schematic representation of the binder jetting printing technology. Powder layers that are added continuously are hardened at the required points using a liquid binding agent.

Figure 6

Overview of the different subtypes of material jetting.

Figure 7

Schematic representation of various material jetting-based printing technologies. All processes rely on the printing material being sprayed drop by drop from a nozzle.

Figure 8

Schematic representation of the acoustic wave jetting. The generation of sound waves is used to spray the print material out of the nozzle.

Figure 9

Schematic representation of the electrodynamic jetting. The printing material is sprayed out of the nozzle with the application of an electric field.

Figure 10

Schematic representation of the microvalve-based printing. The dispensing of the drop-shaped material is controlled by the combination of a magnetized coil and a small plug on the nozzle tip.

Figure 11

Schematic representation of the laser induced forward transfer. Printing material is located on a specially prepared “donor slide” and is sprayed onto a “receiver slide” in droplet form with under usage of a laser source.

Figure 12

Schematic representation of laser guided direct writing. Cells are directed from a liquid solution onto the substrate using a weak laser beam.

Figure 13

Schematic representation of the powder bed fusion. The continuously applied layers of the material powder are hardened at the required points using a laser source.

Figure 14

Schematic representation of the direct energy deposition. An electron beam melts the printing material, which is continuously applied layer by layer at the same time. The melted layers harden as they cool, creating the desired object.

Figure 15

Schematic representation of the sheet lamination. The layers of the intended object are cut out of a continuously running roll of material under usage of a laser source and connected via a laminating roller.