Researchers have made a breakthrough in the fabrication of memory devices using inkjet additive manufacturing (AM) that paves the way for mass production of printable electronics.
A group of researchers at Munich University of Applied Sciences in Germany and INRS-EMT in Canada have demonstrated an additive-manufacturing process using inkjet printing to fabricate resistive memory (ReRAM).
The work is significant because it shows that a complete additive printing process is possible for electronic devices, facilitating the future mass production of flexible electronics through cost-effective printing processes, said Christina Schindler, one of the lead researchers on the project.
"The biggest technological appeal is the mechanical flexibility of our memory tiles, and the fact that all materials required for processing are commercially available," she said.
"Print-on-demand electronics are another large field of possible applications," added Schindler’s co-leader in the research, Andreas Ruediger of INRS-EMT. "At present, the main source of versatile electronics is field-programmable gate arrays that provide a reconfigurable circuitry that can be adopted for different purposes with predefined limitations."
|Christina Schindler of the Munich University of Applied Scientists and Bernhard Huber of INRS-EMT in Quebec in front of their inkjet printer. The two are lead researchers on work to develop an inkjet additive-manufacturing process to fabricate memory, paving the way for mass production of printed electronics. (Source: Munich University of Applied Sciences/INRS-EMT)|
While memory devices are becoming progressively more flexible, their ease of fabrication and integration in low-performance applications have not been the main focus of their research until the group’s work, a paper about which has been published in the journal Applied Physics Letters.
Additive manufacturing—mainly associated with 3D printing—eliminates lithography and material-removal steps at the detriment of feature size, allowing for a streamlined process flow. Inkjet printing is a common office technology that offers the benefit of a straightforward transfer from inkjet to roll-to-roll printing.
The group used a simple principle behind the ReRAM with which it worked, explained Bernhard Huber, a doctoral student at INRS-EMT and working in the Laboratory for Microsystems Technology at Munich University of Applied Sciences.
“In any kind of memory, the basic memory unit must be switchable between two states that represent one bit, or '0' or '1,’” he said. “For ReRAM devices, these two states are defined by the resistance of the memory cell.”
For the conductive-bridge random access memory (CB-RAM) used by the group, "0" is "a high-resistance state represented by the high resistance of an insulating spin-on glass, which separates a conducting polymer electrode from a silver electrode," Huber said. "The '1' is a low-resistance state, which is given by a metallic filament that grows into the spin-on glass and provides a reversible short-circuit between the two electrodes."
The group eschewed printing colors in favor of using functional inks to deposit a capacitor structure comprised of conductor-insulator-conductor with materials already deployed in clean-room processes, he said. "This process is identical to that of an office inkjet printer, with an additional option of fine-tuning the droplet size and heating the target material,” Huber said.
The group plans to continue its work to improve the process and envisions the enablement of print-on-demand electronics that show potential for small and inherently flexible lines of production and end-user products, Schindler said.
"From our proof of concept, we're paving a road toward optimization," she said. "Just imagine supermarkets printing their own smart tags or public transport providers customizing multifunctional tickets on demand. Wearables that explicitly require flexible electronics may also benefit.”
Once the work is optimized, the costs for such a printer to develop electronics could drop to within the range of current inkjet printers, Schindler added.
Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 15 years. She currently resides in a village on the southwest coast of Portugal.