The research paper published in April’s edition of the Advanced Materials journal detailed the use of a customized 3D printer to print electronics onto the skin of a human hand. This research, carried out at the University of Minnesota, represented the latest in an impressive string of breakthroughs in the field of 3D printing technology. As with many innovations – from the PC through to drones – ideas for the commercialization and application to industry of 3D technology were initially limited. Yet, far from remaining a quirky basement hobby for tech enthusiasts, recent developments have included the successful 3D printing of metals – which is now being used by Boeing to produce fasteners for their fleet of aircraft – and now the printing of such metals onto human beings.
The technique used by the researchers involved designing a non-standard 3D printer that could better deal with non-fixed surfaces. Until now, standard 3D printing involved the open-loop method, prior to which the machine would be properly calibrated and then allowed to execute its task. As such, it was clearly inappropriate for dealing with such varied surfaces such as human skin. The researchers eventually came up with a new design for their printer, which uses a closed-loop method and real-time feedback control. This technique allows for direct ink writing onto surfaces which lack a definite, calibratable structures (no two human hands are exactly alike), which can also potentially be moving.
This hybrid technique automatically chooses and places surface-mounted electronic components, combining them with the 3D printing of electrical connects. It represents, in effect, an extension of research already carried out by the same team, in which they demonstrated how to print hydrogels of biological cells onto the skin of laboratory mice.
The lead author of the study, Michael McAlpine, and Associate Professor of Mechanical Engineering at the University of Minnesota, Benjamin Mayhugh, speculated that the technology could have future military applications. Much like a 21 st Century Swiss Army Knife, the printer could be carried in the backpacks of modern soldiers, and be used to print the required tools for their current situation, right there and then. Only, rather than being limited to a blade, screwdriver and such tools, the lightweight 3D printer could be used to print a large variety of electronics and chemical sensors, each customizable in design. And for those concerned about spiraling military budgets, such a machine could set the army back less than $400 – significantly lower than the $578-dollar estimated cost of the modern soldier’s walkie-talkie.
The key to this latest breakthrough is the aforementioned usage of temporary markers, which are applied to the skin, which effectively guide the system as it does its job. The printer uses these markers to scan the surface when printing, all the while using computer vision to check for surface movement and make the appropriate adjustments, all in real time. Designing a system which was capable of doing this was necessary due to the near-impossibility of remaining perfectly motionless for those whose skin is being printed on, for the duration of the process. The new technique allows the printed circuits to keep their shape regardless of the shape or movement of the hand.
As most 3D printing inks need to cure at high temperatures, it was necessary to develop a specialized ink in order to avoid serious skin burns. The team came up with an ink composed of specialized flakes of silver that can both cure and conduct at room temperature. Once printing is complete, the metal can simply be peeled off of one’s skin, or even washed off with water.
In further applications of the technology, not only could soldiers print solar cells to charge electronics, and grafts to directly heal wounds, but also temporary sensors which could detect the presence of enemy chemical and biological agents in time to save lives.
As part of their research, the team worked closely with Dr. Jakub Tolar, one of the world’s leading experts in treating rare skin diseases, and also dean of the medical school at the University of Minnesota Department of Pediatrics. As the potential scope of printing electronics and biological cells directly onto the skin is currently not yet understood, it could merely be a matter of time before we start to hear about the development of advanced treatments for cutaneous conditions.