3D printing or moulding with by-products of the leather industry

Second Skin is a material study that deals with the unused parts of skin in the tanning industry. Excess skin and its valuable ingredients usually stay unused and are disposed of. By chopping and homogenising the skin pieces, a viscous mass is produced. This can be shaped by 3D printing or injection moulding. The gluing properties of the skin create a sturdy, flexible material, which can be optimised for various applications with the aid of enzymes. These enzymes, such as transglutaminase, create cross-links within or between the proteins of the skin – similar to the tanning process of leather.

Injection moulding:
The injection moulding process is attractive due to its cheap production of high volumes. However, the high shrinkage factor of the skin mass, the escaping water and high adhesion to various materials require a technical adaptation of standard injection moulding machines. As new paper injection moulding proves, these requirements for mould and machine can already be achieved by in­dustry today.

3D printing:
To print the skin mass, a ceramic 3D printer is the best choice. They can print pasty masses thanks to a special extruder. Subsequently, the printed object must be dried in the oven. The challenge is to give the skin mass a printable pasty consistency. By adjusting various parameters, such as humidity and the amount of enzyme, this can be regulated.

Transglutaminase catalyses the linkage of protein-bound glutamine and lysine sidechains and forms an isopeptide bond. This means that the collagen in the skin is cross-linked by transglutaminase. In order to test its effectiveness, samples were placed in water. The material which is not crosslinked dissolved over time, while the one with the enzyme remained dimensionally stable.

Manifest by Jakob Müller

student:Jakob Müller