Lin Jr-Lung, Lee Gwo-Bin, Chang Yi-Hsien, Lien Kang-Yi
Department of Engineering Science, National Cheng Kung University, Tainan, Taiwan 701.
Langmuir. 2006 Jan 3;22(1):484-9. doi: 10.1021/la052011h.
The electrowetting on dielectric (EWOD) technique has considerable potential for microfluidic and biomedical applications. The Lippmann-Young model based on the force balance concept has long been used to predict the contact angles of droplets under electrowetting. However, recent experimental evidence has indicated that this model fails to provide accurate predictions of the lower contact angles associated with saturation conditions at higher electric potentials. Hence, the study simulates the internal flow in an actuated droplet and treats it as stagnation-point flow. This kinetic energy is then taken into consideration while calculating the contact angles using an energy balance model. The energy of an actuated droplet is contributed by the combination of the side surface tension energy, the base tension energy, the dielectric energy, and the kinetic energy when deriving the energy balance model. Consequently, the new energy balance model modifies the Lippmann-Young equation, thereby providing enhanced reasonable predictions of the droplet contact angle across the higher electric potential where the contact angles are close to the saturated condition.
介电电泳（EWOD）技术在微流控和生物医学应用方面具有巨大潜力。基于力平衡概念的 Lippmann-Young 模型长期以来一直用于预测电润湿条件下液滴的接触角。然而，最近的实验证据表明，该模型无法准确预测在较高电势下与饱和条件相关的较低接触角。因此，该研究模拟了驱动液滴内的内部流动，并将其视为驻点流。在使用能量平衡模型计算接触角时，会考虑这种动能。在推导能量平衡模型时，驱动液滴的能量由侧面表面张力能、底面张力能、介电能和动能共同构成。因此，新的能量平衡模型修正了 Lippmann-Young 方程，从而在接触角接近饱和条件的较高电势范围内，对液滴接触角提供了更合理的预测。
