Planarization of Rough UV Polymer Substrates for Microfluidic Pixel Applications
Sprache des Vortragstitels:
Microelectronic Systems Symposium 2018
Sprache des Tagungstitel:
In this work we present a roll to plate fabricated UV- Stereolithography (UV-SLA) polymer structure, which can be used as a substrate for microfluidic pixel applications, driven by Electrowetting-On-Dielectric (EWOD) forces. Electrowetting-On-Dielectric is a surface tension driven effect, which affects the surface tension equilibrium between the three governing phases of a fluid-gas-solid system. This equilibrium is given by the well-known Young Law. The contact angle ?0 denotes the angle between the fluid interface and the substrate with dielectric and hydrophobic layering, without any external forces except gravity. Applying a voltage beyond the droplet´s triple contact line leads to a change in the surface tension equilibrium and therefore a new equilibrium contact angle ?V, given by Lippmann Young´s law.
We show how to fabricate Electrowetting-On-Dielectric test structures on rough UV-SLA polymer surfaces by planarizing the substrate with a negative photoresist right before the electrode lift off process. The planarization and lift off procedure will enable us to insert hydrophobic layers of low surface roughness inside chambers of different height, in particular the reservoir chamber and the visible pixel channel. The fluid moves between the reservoir, hidden behind an intransparent small shutter platelet, and the visible fluid channel, switching the pixel on and off. In an upright orientation, the fluid flows back to the reservoir chamber, supported by gravitational forces, after switching off the electrowetting actuation voltage. FEM simulations will support the functional principle and help with certain design choices, to subsequently fabricate a working pixel prototype.