Abstract
Introducing spacers into pixelated electrowetting displays (EWDs) normally gives mechanical strengthening, while bringing undesired disturbance of water/oil interfacial dynamics. Hence, spacer array is a key pixel structure needs careful consideration in the design and fabrication of electrowetting displays. Here, we propose a spacer array, which is designed standing on the junction of adjacent pixel walls, fabricated by photolithography. The spacer array provides mechanical strength enhancement and reliable oil motion controllability. By optimizing the spacer distribution density, the EWD device may achieve 28% increase in open ratio (white area fraction) and withstand 60 N/mm2 pressure. This design of spacer array reasonably solves the contradiction between mechanical strength enhancement and optoelectronic performance in EWDs, providing potential applications in oil–water two-phase microfluidic devices.
Highlights
Electronic paper-like (e-paper) displays have attracted more and more attentions because of their natural light reflection property, which gives unique advantages in portable reading, electronic shelf-labels, tablets, billboards, etc. [1,2,3] Electrowetting display (EWD) reported in 2003 is a very promising display technology, which enables full color and video contents playing on e-paper devices for the first time [4]
An extra pin structure (EPS) or hydrophilic/hydrophobic microparticles in pixels have induced the reorganization of oil film to different thickness distributions during the filling process, resulting in improved oil motion controllability after the oil film rupturing from the thinnest point [10,16]
When the insulator was thermo reflowed back to hydrophobic (Figure 1c1,d2), oil could be filled into pixels (Figure 1d1,e2), to finish the fabrication of electrowetting displays (EWDs) display with assembly
Summary
Electronic paper-like (e-paper) displays have attracted more and more attentions because of their natural light reflection property, which gives unique advantages in portable reading, electronic shelf-labels, tablets, billboards, etc. [1,2,3] Electrowetting display (EWD) reported in 2003 is a very promising display technology, which enables full color and video contents playing on e-paper devices for the first time [4]. After the switching-on process with a bias voltage, the colored oil in EWD display is repelled to be an oil droplet at the side or the corner of a pixel with the decreasing θ (Equation (1)). An extra pin structure (EPS) or hydrophilic/hydrophobic microparticles in pixels have induced the reorganization of oil film to different thickness distributions during the filling process, resulting in improved oil motion controllability after the oil film rupturing from the thinnest point [10,16]. A spacer structure owning enough mechanical strength and good oil motion controllability is needed for EWD display, which is a big challenge. The mechanical strength and oil motion controllability enabled by the spacer array introduced into the EWD device have been studied. The influences of the distribution density and length scale of the spacer array are investigated
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