Field of tissue engineering, biofabrication, and regenerative medicine are continually growing due to the increasing life expectancy of humans. The most promising technique in these fields is 3D bioprinting allowing direct deposition of various types of materials and cells. Even though 3D printing has shown to be promising, there are still several limitations like low resolution, the challenging printing of hollow tubular structures with low wall thickness due to high shear rates, and low cell alignment. 4D biofabrication is a technique where the fourth dimension is introduced by using smart materials, that are capable to undergo shape transformation after the addition of certain stimuli. The fourth dimension offers advantages as hollow structure fabrication, various shape formations, and preservation of 2D patterns in the 3D structure. Based on the design using 4D biofabrication it is possible to fabricate highly complex structures with specific/ uniaxial cell alignment that resembles blood vessels, muscle tissues, lungs, etc.

In comparison to regular 3D printing, using 4D biofabrication it is possible to obtain hollow tubular structures with extremely small diameters of 20 µm, which can mimic the wide range of diameters of natural blood vessels [1]. Nevertheless, we have as well used various other techniques like electrospinning and meltelectrowriting in combination with 3D printing to design tubular structures that would provide cell alignment cues, to use these structures for highly aligned tubular structure tissues like skeletal muscle and nerve [2-5]. Based on materials used and their actuation we were able to achieve superfast shape transformation 10 s. Thus 4D biofabrication is a highly promising approach in the field of tissue engineering for the fabrication of hollow tubular structures with high resolution.