Hybrid 3D Printing Technique Yields Unique Wearable Devices

Researchers at Harvard University’s Wyss Institute and the Air Force Research Laboratory have come up with a new hybrid 3D printing technique for use in wearable electronics. To make these devices, conductive ink made out of thermoplastic polyurethane (TPU) mixed with silver flakes is printed on a flexible substrate. Since these conductors are precisely positioned, surface-mount components can then be placed in the exact position as needed.

Besides precise placement, what makes this technique even more useful is that the resistance of the conductive material changes as it is stretched, meaning it can detect when a joint is bent. The printing method can even be used to form alternating layers of insulating and conducting TPU in order to form a pressure sensor.

Soft sensors composed of conductive materials that exhibit changes in their electrical conductivity when stretched (which is how they detect movement) are coupled with a programmable microcontroller chip to process those data, as well as a readout device that communicates the data in a form humans can understand. To achieve this, the researchers combined the printed soft sensors with a digital “pick-and-place process” that applies a modest vacuum through an empty printing nozzle (through which ink is normally dispensed) to pick up electronic components and place them onto the substrate surface in a specific, programmable manner.

Ultimately, this work will help overcome a barrier to wearable electronics that track and measure the body’s movements, especially integrating rigid electrical components on or within skin-mimicking matrix materials. You can read more about the Harvard team’s research here, or check out the video below!