Permanent Epoxy Photoresist for Pixel Grids in Electrowetting

In electrowetting, liquid surface tensions are modified by applying a field potential. With no voltage applied, colored oil lies flat between water and the electrode within a defined well. When a voltage is applied between the electrode and water, the tension changes and the water then forces the oil aside.

In electrowetting displays (EWD), the use of an active matrix TFT back-plane can control each pixel allowing for high speed and video content. Because electrowetting is low power, this is an attractive technology for many applications. Electrowetting displays can also be used in both reflective and transmissive modes and offer higher brightness compared with other reflective technologies.

Electrowetting is also used for a wide range of microfluidic lab-on-chip applications.

SU-8: Benefits/Attributes

  • Highly crosslinked system with high structural strength
  • High contrast with vertical sidewalls
  • High aspect ratio imaging
  • High fill factor pixel walls
  • Ability to adhere to fluoropolymers
  • Fast photospeeds for high volume manufacture
SU-8 Pixel Walls with oil shown in the on, mid and off state
Transmissive display using an SU-8 Grid

Courtesy of University of Cincinnati, Plastics Electronics 2010

SU-8 Material Properties

Dielectric Constant4.1 @ 1GHz
Volume Resistance2.8×1016Ω/cm
Surface Resistance1.8×1917Ω/cm

SU-8 2000 Pixel Walls
Source: MicroChem Applications Lab
SU-8 2000 Pixel Walls
Source: MicroChem Applications Lab