Influence of surface coatings on surface free energies and wettability of printed-electronics substrates

Introduction

Printed electronics have recently received a growing interest due to their potential with regards to flexible and/or low-cost electronics. The inherent compatibility of printing technologies with soft, polymeric, or biologic materials renders them a promising new fabrication tool - particularly for bioelectronics or point-of-care applications1. Since most materials in printing are handled in liquid form (e.g. solutions, suspensions, or mono-/oligomers of the final material) their wetting behavior on the substrate exerts a strong influence on the quality of the fabrication outcome. For instance, differences in contact angle hysteresis can decide on whether a material shows stable or instable line behavior or even dewetting2. Recently, epoxy-based coating have been shown to yield significant improvements in adhesion and wetting behavior of conductive inks3. The present project is aimed at expanding this approach by mechanistically investigating the effect of different polymer mixtures on the wetting behavior of the resulting surface and – consequently – the print behavior and quality.

Aim & Research Methods

The project aims at designing versatile polymer coatings that allow precise control over the polar and dispersive components of surface energy. Further, the influence of surface energies on the print behavior of different inks (e.g. conductive silver nanoparticle or carbon inks as well as dielectric inks) will be investigated. To this end, you will…

  1. …establish protocols to determine the polar and dispersive components of surface energies,…
  2. …develop polymer mixtures that can be spin-coated onto printed electronics substrates and allow control over the surface energy components, and…
  3. …evaluate the influence of the polymer coatings on the print behavior of different inks.

In doing so, you will be introduced to an interdisciplinary working environment and will learn the following techniques:

  1. Optical measurements of contact angles and surface energies (pendant drop method)
  2. Spin-coating of thin films and related analysis tools (optical profilometry and roughness measurements)
  3. Inkjet printing of conductive and dielectric inks

Requirements

We are looking for a highly dedicated and motivated candidate to work on an interdisciplinary research topic. The candidate should offer:

  1. Excellent analytical and experimental skills
  2. A solid background in polymer chemistry and surface/interface physics
  3. Programming skills for data analysis (e.g. Matlab or Python) are beneficial

Possible starting date & further information

Potential starting date is as soon as possible. For further details and application contact Philipp Rinklin.

References

  1. T. Someya, Z. Bao, and G. G. Malliaras, Nature 540, 379 (2016).
  2. P. C. Duineveld, Journal of Fluid Mechanics 477, 175 (2003).
  3. K.-Y. Shin, M. Lee, H. Kang, K. Kang, J. Y. Hwang, J.-M. Kim, and S.-H. Lee, Journal of Electrical Engineering and Technology 8, 603 (2013).