The increased interest in pharmaceutical, chemical, and biomedical/genetic analysis and diagnostics has led to the development of numerous micro-electromechanical systems (MEMS) based fluid handling and mixing systems. The majority of these systems is based upon either the employment of continuous-flow systems, or provide for discrete sample manipulation through the use of external, macro-scale, appliances (e.g., syringe pumps, centrifugal acceleration field, etc.). In contrast to these approaches, we propose to develop a platform to manipulate individual droplets using an electrically addressed control system. Utilizing the Electrowetting Effect, the solid-liquid surface energy will be manipulated using a microfluidic platform formed from an array of controllable electrodes. Decreases in the solid-liquid surface energy causes a corresponding decrease in the contact angle at the liquid-solid-vapor line, resulting in a pressure imbalance between the two ends of the droplet, causing the droplet to move. This approach utilizes the most dominant physical force that is present in microfluidic sample handling: interfacial surface tension. Tanner Research, Inc. and the Keck Graduate Institute (KGI) are proposing to develop enabling technology, utilizing electrowetting arrays, for motion control of nanoliter sized droplets. By the end of Phase I, Tanner Research and KGI will have demonstrated a set of simple droplet manipulations, including combination and translation, on a series of candidate electrowetting arrays developed and fabricated at Tanner Research's Micro Fabrication facility. By completion of the Phase II effort, we will have developed a complete electrowetting array and control system and will have demonstrated both a cDNA microarray hybridization assay and a sample preparation protocol using this electrowetting platform.
