Tensile Testing of Metal Nanoparticles Printed on
Polymer Substrates
Steven Wu
Interdisciplinary Engineering and Management, Honors Program
Clarkson University, Potsdam, NY
Mentor: Dr. John Moosbrugger
Professor, Mechanical and Aeronautical Engineering
Clarkson University, Potsdam, NY
Printing of metal nanoparticles on various substrates utilizing inkjet technology has great
potential for some applications requiring conductive films. A dispersion of metallic nanoparticles can be
placed inside inkjet cartridges and printed with precision. Silver nanoparticles can be sintered at
temperatures much lower than the melting point of bulk silver, saving significant amounts of energy and
allowing the use of lower temperature substrates, such as polymers. The process also avoids the waste
associated with wet, electrochemical methods and it has low fixed capital costs. This method is
particularly suited for flexible electronics with applications in medical technology as well as in
commercial products such as data recorders within the body and foldable screens. One example is organic
light emitting devices (OLED), which are being developed as alternatives to liquid crystal displays
(LCD). The OLED uses polymer-based substrates, which allow for ductility [1]. OLED technology has
potential in lighting, alphanumeric displays, and full color flat panel displays [2]. Lower production costs
for electronics and greater flexibility will lead to faster, cheaper, and more versatile electronic systems in
the future.
The mechanical properties of a sintered nanoparticle film (film thickness ~ 1µm) may be
significantly different than those of bulk metals as typical fracture bands in bulk materials exceed the size
of thin micrometric films [3]. These properties have proven difficult to measure with great accuracy.
Current testing methods include thermal bending, X-ray diffraction, interferometer, vibration reed
technique, nanoindentation, and tensile testing [4]. Based on the work of Várguez, Avilés, and Oliva
(2008), we are conducting tensile tests to examine specimen responses to applied tensile strain. It is
critical to understand the mechanical properties of the films as this will impact the extent to which OLED
and other displays can be bent [1]. Because it is more difficult to test the film on its own, it would first be
Steven Wu, 2008, Engineering and Management, Honors Program
Mentor: Dr. John Moosbrugger, Department of Mechanical and Aeronautical Engineering
printed onto a substrate and tested. The results, when compared to the same tests done on the substrate
alone, would allow for extrapolation of the properties of the film.
A LabVIEW Virtual Instrument program was written to record the data collected by the tensile
tester which employed a motor driven system connected to a five pound load cell. In developing the
process, specimens were printed onto 0.13 mm thick transparency film with a pattern of reference points
within both the crossheads and gauge section. These points can be used to examine the heterogeneity of
deformation within the specimen. The detailed specimen design is shown in Figure 1. Specimens were
deformed in tension at a constant rate of extension of 0.5mm/min.
Figure 1: Details of the specimen design (all dimensions in mm). The out-of-plane thickness is
0.13mm
The gauge section of the specimen was imaged using an optical microscope, on top of which was
mounted a camera to acquire images of the gauge section. Tensile force response and crosshead
displacement were recorded using LabVIEW.
Most of the specimens sustained tensile strains of over 20% based on the crosshead displacement
before the tests had to be terminated to prevent damage to the 5 lb. load cell. For those that deformed to
final rupture, failure resulted primarily from geometric defects created during the cutout of the specimen.
Lacking a precise method to cut the specimens from the film substrate after printing, the process was done
by hand and resulted in flaws in the specimen geometry.
Steven Wu, 2008, Engineering and Management, Honors Program
Mentor: Dr. John Moosbrugger, Department of Mechanical and Aeronautical Engineering
References:
[1] Leterrier, Y., Fischer, C., Médico, L., Demarco, F., Månson, J.-A.E., Bouten, P., DeGoede, J., Nairn, J.A.
(2003). Mechanical properties of transparent functional thin films for flexible displays.
[2] Bale, M., Carter, J.C., Creigton, C., Gregory, H., Lyon, P.H., Ng, P., Webb, L., Wehrum, A. Ink jet printing: The
route to production of full color P-OLED displays. Cambourne Business Park
[3] Kraft, O., Schwaiger, R., Wellner, P. (2001). Fatigue in thin films: lifetime and damage formation. Materials
Science and Engineering, A319-321
[4] Avilés, F., Oliva, A.I., & Várguez, P. (2008). Mechanical properties of gold nanometric films onto a polymetric
substrate. Surface and Coatings Technology. 202
Steven Wu, 2008, Engineering and Management, Honors Program
Mentor: Dr. John Moosbrugger, Department of Mechanical and Aeronautical Engineering