Improving the dielectric properties of an electrowetting-on-dielectric microfluidic device with a low-pressure chemical vapor deposited Si₃N₄ dielectric layer

Dielectric breakdown is a common problem in a digital microfluidic system, which limits its application in chemical or biomedical applications. We propose a new fabrication of an electrowetting-on-dielectric (EWOD) device using Si₃N₄ deposited by low-pressure chemical vapor deposition (LPCVD) as a dielectric layer. This material exhibits a greater relative permittivity, purity, uniformity, and biocompatibility than polymeric films. These properties also increase the breakdown voltage of a dielectric layer and increase the stability of an EWOD system when applied in biomedical research. Medium droplets with mouse embryos were manipulated in this manner. The electrical properties of the Si₃N₄ dielectric layer—breakdown voltage, refractive index, relative permittivity, and variation of contact angle with input voltage—were investigated and compared with a traditional Si₃N₄ dielectric layer deposited as a plasma-enhanced chemical vapor deposition to confirm the potential of LPCVD Si₃N₄ applied as the dielectric layer of an EWOD digital microfluidic system.