AbstractDevelopments of robust microfluidic tools that can manipulate fluids and their contents quickly, easily and without the need for an experienced operator are important requirements in portable diagnostic devices. Among many possible techniques for fluidic pumping and delivering, pressure driven actuation and electrokinetic (EK) flows are the two predominant methods of pumping fluids through small microchannels. Pressure driven devices, however, require large pneumatic support systems and on-chip moving parts that can cause mechanical failure and tedious fabrication process. Electrokinetic pumps do not require moving parts or large off-chip support systems. Traditional EK pumps, however, can suffer from Joule heating, electrode decomposition, and fluid contamination problems due to direct liquid contact with metal electrodes. The bulky volume also makes EK pump integrations become difficult. To overcome these drawbacks, we demonstrate a novel contactless chip-embedded EK pump with polydimethylsiloxane (PDMS) membranes that isolate gallium metal electrodes from the working fluid. Pumping capability was tested and quantified for two different microfluidic channel geometries: a closed circuit ;;Loop” design and a hydrodynamic resistance free ;;T-shape” design. Maximum pump pressure and flow rate are 51Pa and 0.3μl/min, respectively, when 2000V is applied. We then utilize these contactless EK pumps by inserting multiple units into a fluid delivery and control system and sample plug loading system in order to demonstrate their implementations and automation capabilities. This novel contactless gallium pump demonstrates less mechanical failure, lower cost, and higher portability than current EK pumps. This design will facilitate micro-electro-system and lab-on-chip product development and expand their applications in biological study and analytical chemistry.
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Contactless metal-based EK pump and potential implementations
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