Electrical conductivity enhancement in inkjet-printed narrow lines through gradual heating

Abstract

Conductive silver lines of various widths (0.04-40 mm) were fabricated with dilute silver-nanoparticle ink on polyimide films using an inkjet printer. The electrical properties of the lines were found to vary in width. In particular, wider lines (>0.4 mm) exhibited low resistivity (3.6-5.4 μ cm), approaching that of bulk silver (1.6 μ cm). On the other hand, narrower lines (<0.3 mm) exhibited much higher resistivity (14.6-16.5 μ cm), presumably because of the so-called coffee-ring effect. This effect, known to strongly influence nanoparticle deposition, is caused by convection flow, during which nanoparticles segregate at the line edge. However, when the narrower lines were heated slowly from 20 • C to 200 • C at a heating rate of 3 • C min −1 to reduce convection flow, the nanoparticles redistributed uniformly, after which the lines exhibited low resistivity (3.9-4.2 μ cm). Therefore, gradual heating appears to be an excellent method for enabling inkjet printing technology to yield narrow highly conductive lines.

Spraying dynamics in continuous wave laser printing of conductive inks

“…The influence of NP concentration on the obtained electrical resistivity can be due to the poor electrical contact among NPs at decreased concentrations, as well as to an overestimation of the filled volume fraction in the presence of voids, which translates into a higher apparent resistivity. A similar behavior has been reported for printed Ag lines showing a ‘coffee-ring effect’ 46 .…”

Suppressing the coffee-ring effect of colloidal droplets by dispersed cellulose nanofibers

“…The point is not the circular ring but the non-uniform distribution of particles, where the inner part of the droplet endsup at a lower density. The non-uniform thickness of the colloidal film degrades the coating of paints and clarity of printed characters on paper, and the shapes of cross sections of particulate films substantially affect the electric conductivity in printed electronics [ 19 , 20 ]. The conducting wires are desired to have as low electric resistance as possible, and the elements of a heater should have a specified value of resistance [ 4 ].…”

Characterizing Metal Nanoparticle Films: A Methodology Using Surface Micromachining by Direct Printing

“…Gradual heating/cooling the samples prevents crack formation by reducing the film's thermal shock. It has also been observed that the gradual heating/cooling improves film thickness uniformity [5]. It is likely that the total drying time could be reduced through process optimization, but this was not the focus of the current work.…”