University of Illinois researchers have produced a nanoparticle-based silver ink that finds application in a rollerball pen, which is a ball-point pen with a larger roller, made mostly by plastic, to trace electrical connections for flexible LED displays and other devices.
The silver-particle-based conductive inks are used on rigid surfaces. While this new ink can draw on paper or folded paper for nearly a radius of 0.5 mm, nearly 1000 times before the ink drains, favoring flexible and rollable displays.
A 12 µm thickness rolled ink has a very low electrical resistivity of 1.99 x 10-4 ohm-cm, which in turn can be lowered to 4.34 x 10-6 Ω cm by annealing it. Silver offers 45% to 55% of ink's weight with viscosity ranging from 1 to 10 Pa-s. A material mostly found in cosmetics and household products, Hydroxyethyl cellulose is used as a binder.
CircuitWriter pen, a conventional conductive pen, developed by Caig laboratories, Poway, CA, forms a film with same thickness between 10 and 25 µm. It also contains silver and uses acrylic as a binder. It has a solid weight proportion of 51.5%. The producers advise not to use the ink on surfaces that are meant to be flexed.
Metallic inks is being used in inkjet printers to fabricate electronic devices, but the rollerball pen with a nanoparticle-based ink offers flexibility to draw directly on paper or other rough surfaces , at low expenses and without any programming.
The major advantage of this pen is it is a hand-held writing tool that replaces costly printers and printheads required for inkjet or other printing approaches, said Lewis, affiliated member of Beckman Institute for Advanced Science and Technology.
Besides, researchers of University of Illinois have demonstrated a 3D radio-frequency antennas, conductive text and flexible LED display on paper.
Source: www.illinois.edu