A flexible array of LEDs mounted on paper. Hand-drawn silver ink lines form the interconnects between the LEDs. Photo: Bok Yeop Ahn |
The pen may have bested the sword long ago, but now it’s
challenging wires and soldering irons.
Univ.
of Illinois engineers
have developed a silver-inked rollerball pen capable of writing electrical
circuits and interconnects on paper, wood, and other surfaces. The pen is
writing whole new chapters in low-cost, flexible, and disposable electronics.
Led by Jennifer Lewis, the Hans Thurnauer professor of materials
science and engineering at the U.
of I., and Jennifer
Bernhard, a professor of electrical and computer engineering, the team published
its work in Advanced Materials.
“Pen-based printing allows one to construct electronic
devices ‘on-the-fly,'” said Lewis, the director of the Frederick Seitz
Materials Research Laboratory at the U. of I. “This is an important step toward
enabling desktop manufacturing (or personal fabrication) using very low cost,
ubiquitous printing tools.”
While it looks like a typical silver-colored rollerball pen,
this pen’s ink is a solution of real silver. After writing, the liquid in the
ink dries to leave conductive silver pathways—in essence, paper-mounted wires.
The ink maintains its conductivity through multiple bends and folds of the
paper, enabling devices with great flexibility and conformability.
Univ. of Illinois engineers developed a pen with conductive silver ink that can write electric circuits and interconnects directly on paper and other surfaces. Photo: Bok Yeop Ahn |
Metallic inks have been used in approaches using inkjet
printers to fabricate electronic devices, but the pen offers freedom and
flexibility to apply ink directly to paper or other rough surfaces instantly,
at low cost and without programming.
“The key advantage of the pen is that the costly printers
and printheads typically required for inkjet or other printing approaches are
replaced with an inexpensive, hand-held writing tool,” said Lewis, who is also
affiliated with the Beckman Institute for Advanced Science and Technology.
The ability to create freestyle conductive pathways enables
new possibilities in art, disposable electronics and folded three-dimensional
devices. For example, the researchers used the silver pen to sketch a copy of
the painting “Sae-Han-Do” by Jung Hee Kim, which portrays a house, trees, and
Chinese text. The ink serves as wiring for an LED mounted on the roof of the
house, powered by a five-volt battery connected to the edge of the painting.
The researchers also have demonstrated a flexible LED display on paper,
conductive text and three-dimensional radio-frequency antennas.
Next, the researchers plan to expand the palette of inks to
enable pen-on-paper writing of other electronic and ionically conductive
materials.
