The 3D printed graphene formula was developed by Ramille Shah and Mark Hersam’s teams at Northwestern. The inks themselves are made up of graphene powder, a biocompatible and biodegradable elastomer (polylactide-co-glycolide) and a mixture of solvents. “When combined in the proper ratios, we can make a 3D printable ink that contains mainly graphene, explains Shah. “And although initially a liquid suspension, when we extrude it from a nozzle, it rapidly solidifies into a self-supporting structure.”

The inks are also tailored in such a way that they remain wet enough after extrusion to seamlessly merge with previously deposited 3D-printed layers and other materials, she adds. “In this way, we can construct small objects (less than 1 mm in size) and large objects (several centimetres across) made up of single or many hundreds (or even thousands) of graphene layers. We can handle these objects straight away after printing.”

Most conductive, non-metallic 3D printed material

The 3D printed composite has numerous unique physical, mechanical, electrical and biological properties. Since it contains graphene in the most part, it should be incredibly fragile and brittle. However, this is not the case and it is very plastic and malleable. Indeed, sheets of the material can be rolled, stretched, folded, cut and even sutured to soft biological tissue.

“Although not as conducting as pristine single sheet graphene, we believe this to be the most conductive, non-metallic material to have been 3D printed, which also happens to be biocompatible,” Shah tells nanotechweb.org. Along with these unique physical and electrical properties, 3D graphene also appears to help regenerate damaged nerve and cardiac tissue – all without added neurogenic factors or other external stimuli. The material is biocompatible too when implanted in mice and it rapidly vascularises and fixes to host biological tissue.

Complex tissue engineering and regenerative medicine

And that is not all: combined with the fact that it can be 3D printed into almost any shape (including architectures based on a patient’s CT- or MRI-scan), 3D printed graphene could perhaps be the ideal material for nerve, muscle, cardiac and complex tissue engineering and regenerative medicine applications, adds Shah. Such applications could also be extended to implantable electronics and biosensors.

The Northwestern researchers, reporting their work in ACS Nano DOI: 10.1021/acsnano.5b01179, are now busy looking into in vivo applications for their 3D material based on its ability to regenerate damaged nerve and cardiac tissue. “We are also investigating the possibility of combining it with other 3D printable ink systems developed in our lab for engineering more complex nerve, muscle and bone tissue composite structures,” adds Shah. “We will also be exploring its potential for non-biomedical devices, such as biodegradable electronics and sensors.”