A new process for printing stretchable electronic sensory devices in 3D has been developed by engineering researchers at the University of Minnesota. This development could enable robots to feel their environment. The discovery has also been hailed as a major step forward in printing electronics on real human skin.

Michael McAlpine, a University of Minnesota mechanical engineering associate professor and lead researcher on the study noted that the stretchable electronic fabric has many possible applications. Equipping surgical robots with this type of ‘bionic skin’ would allow surgeons to actually feel during minimally invasive surgeries. This would make surgery easier instead of using cameras as is done now. The sensors could also enable other robots to walk and interact with their environment easier.

McAlpine, gained international recognition in 2013 for integrating electronics and novel 3D-printed nanomaterials to create a “bionic ear”. He added that this new technology could also be used to print electronics on real human skin. This ultimate wearable technology could eventually be used by soldiers in the field to detect dangerous explosives or chemicals, or for health monitoring.

Although the team has not printed on human skin yet, they were able to print on the curved surface of a model hand using the technique. A printed device was also interfaced with the skin and the team was surprised that the device was sensitive enough that it could detect a pulse in real time.

The unique sensing fabric was manufactured with a one-of-a kind 3D printer the team built in the lab. The multifunctional printer has four nozzles to print the various specialized “inks” that make up the layers of the device:

A base layer of silicone Top and bottom electrodes made of a conducting ink A coil-shaped pressure sensor A sacrificial layer that holds the top layer in place while it sets.

The supporting sacrificial layer is washed away in the final manufacturing process.

All of the layers of “inks” used in the flexible sensors can set at room temperature. This is significant as conventional 3D printing uses liquid plastic that is too hot and too rigid to use on skin. The flexible 3D printed sensors can stretch up to three times their original size.

McAlpine explained that this is a unique new way to approach 3D printing of electronics. The multifunctional printer used can print several layers to make these flexible sensory devices. This development could be applied to many different fields, including energy harvesting, health monitoring and chemical sensing.

The team members say the best part of the discovery is that the manufacturing is built into the process. McAlpine noted that with most research, when something new is discovered it then needs to be scaled up. This process could take years before the technology is ready for use. With this development, the manufacturing is built into the process, so it is ready to go right now.

The next step in the research is to move toward semiconductor inks and printing on a real body. McAlpine concluded by describing the possibilities for the future as endless.

The full study was published in the journal Advanced Materials.