An Open-configuration Electrowetting-based Biofluidics Actuation for Preventing Biomolecular Adsorption

Electrowetting-on-dielectric (EWOD) is a new method for moving liquids in micro-total-analysis system. One of the biggest challenges for all EWOD-based biofluidic chips is preventing and minimizing nonspecific adsorption of biomolecules on the hydrophobic surfaces. In this paper, we theoretically and experimentally analyze the adsorption in EWOD, which is mainly induced by hydrophobic interaction and electrostatic attraction. An open-configuration EWOD with only one hydrophobic surface, instead of the traditional sandwiched EWOD with two hydrophobic surfaces, is exploited to minimize the hydrophobic interaction. The manipulation modes are also optimized to decrease electrostatic attraction by limiting the duty-ratio of the applied pulse voltage. In experiments, the analyte is a 1:1 (v/v) mixture of 10 mug/ml bovine serum albumin (BSA) solution with pH 7.4 phosphate buffers and 10 mug/ml hen egg white lysozyme solution with pH 7.4 phosphate buffers. A rapid transportation speed of the 1.5 mul mixture droplet as high as 14 mm/s is successfully achieved in air by applying a 2.5 Hz 40 V_dc pulse voltage with the 12.5% duty-ratio. The fabrication process of the silicon-substrate actuator is IC compatible, thus a miniaturized biofluidic system integrated with peripheral circuits is technically feasible