Production Considerations for Bistable Droplet Driven Electrowetting Displays Andriy Bitman*, Frank Bartels*, Jürgen Rawert*, Karlheinz Blankenbach** *advanced display technology GmbH, Dortmund, Germany **Display Lab University Pforzheim, Pforzheim, Germany Abstract The electrowetting displays are widely discussed within the last years. A colored liquid is deformed or moved from a visible to a non-visible position. The production aspects of such microfluidic structures has to cover microfluidic channel structures, filling procedures, sealing, temperature stability and - electrodes for matrix driving. The requirement of reasonable production costs need to balance these requirements. We will show some examples how the design and production is realized and will present some cost consideration. Author Keywords electrowetting; bistable; reflective; sunlight readability; production; passive matrix 1. Introduction Electrowetting displays were first reported in 1981 [1]. It lasted about two decades until first electrowetting displays were presented by LIQUAVISTA [2]. In 2006, the adt- team (see authors) introduced bi-stable electrowetting prototypes [3]. Over the past years, the interest in electrowetting grew and other teams like GAMMA DYNAMICS [4] and ITRI [5] introduced further approaches. The reflective displays based on electrowetting effect are widely discussed within the last years. A colored liquid is deformed or moved from a visible to a non-visible position. In LCD production a liquid is an ingredient of high impact, but in such electrowetting devices the fluidic aspects are much more important. The approach of adt’s bistable electrowetting principle (see e.g. [6], [7]) is the true bistability by positioning the droplet in two individual positions, one visible the other not (reservoir position) and a fluidic barrier in between. This two chamber concept has its biggest impact for larger droplet sizes of 0,5 to 5 mm. The intention of our work presented in this paper is to show actual production steps to realize such a fluidic display at reasonable cost. We use industrial available technologies including filling and assembly processes, electrode positioning and electrical connections. We will give some considerations regarding this topic and will show some examples how the design and production is realized. In addition we will discuss the overall potential of the technology to be transferred to large area productions processes like roll to roll, embossing or molding. 2. Fluidic layer design Fig. 1 shows the principal setup of devices realized by adt’s droplet driven display. In the 2D approach a colored droplet is transported from a visible to a non visible position using electrowetting. In both positions the droplet is stable in a fluidic chamber, if the voltage is removed. Fig. 1: 2D and 3D electrowetting displays setup Fig. 2 Electrode layer for 2D setup In order to get the droplet through the barrier, we need four electrodes, one in each chamber and one on each entrance area before the barrier. In Fig. 2 two of such electrodes, realized by laser structured ITO, are given. The electric field is than valid between one of such individual electrode and a common top electrode. The 3D-approach offers a much better aperture, but the fluidic structure has to be produced in two layers separated 62.3 / A. Bitman 846 • SID 2012 DIGEST ISSN 0097-966X/12/4302-0846-$1.00 © 2012 SID