Because these surface-mounted electrical components (e.g., LEDs, resistors, micro-chips) are by nature hard and rigid, the team took advantage of TPU’s adhesive properties by applying a dot of TPU ink beneath each component prior to attaching it to the underlying soft TPU substrate. Once dried, the TPU dots serve to anchor these rigid components and distribute stress throughout the entire matrix, allowing the fully assembled devices to be stretched up to 30% while still maintaining function. A device composed of 12 LEDs attached to a flat TPU sheet created using this method was able to be repeatedly bent into a cylindrical shape without reduction in the intensity of the LEDs’ light or mechanical failure of the device.
As a simple proof-of-concept, the team created two soft electronic devices to demonstrate the full capabilities of this additive manufacturing technique. A strain sensor was fabricated by printing TPU and silver-TPU-ink electrodes onto a textile base and applying a microcontroller chip and readout LEDs via the pick-and-place method, resulting in a wearable sleeve-like device that indicates how much the wearer’s arm is bending through successive lighting-up of the LEDs. The second device, a pressure sensor in the shape of a person’s left footprint, was created by printing alternating layers of conductive silver-TPU electrodes and insulating TPU to form electrical capacitors on a soft TPU substrate, whose deformation patterns are processed by a manual electrical readout system to make a visual “heat map” image of the foot when a person steps on the sensor.
While the team is continuing to optimize both their materials and their methods, hybrid 3D printing is broadly applicable to manufacturing myriad electronic devices. “We have both broadened the palette of printable electronic materials and expanded our programmable, multi-material printing platform to enable digital ‘pick-and-place’ of electronic components. We believe that this is an important first step toward making customizable, wearable electronics that are lower-cost and mechanically robust,” says Lewis, who is the corresponding author of the paper, a Core Faculty member at the Wyss Institute, and the Hansjörg Wyss Professor of Biologically Inspired Engineering at SEAS.
“This new method is a great example of the type of cross-disciplinary collaborative work that distinguishes the Wyss Institute from many other research labs,” says Wyss Founding Director Don Ingber, M.D., Ph.D., who is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School and the Vascular Biology Program at Boston Children’s Hospital, as well as a Professor of Bioengineering at Harvard SEAS. “By combining the physical precision of 3D printing with the digital programmability of electronic components, we are literally building the future.”
Additional authors of the study include Travis Busbee, a graduate student in the Lewis lab and co-founder of Voxel8; Jordan Raney, Ph.D., former postdoc in the Lewis lab and current Assistant Professor in the School of Engineering and Applied Sciences at the University of Pennsylvania; Alex Chortos, Ph.D., and a postdoc in the Lewis lab; Arda Kotikian, a Graduate Research Fellow in the Lewis lab.
This research was supported by the Air Force Research Laboratory Materials and Manufacturing Directorate and UES, the Vannevar Bush Faculty Fellowship Program under the Office of Naval Research, a generous donation from the GETTYLAB, and the Wyss Institute at Harvard University.
Source: Wyss Institute- Harvard University
Leave a comment