Experimental study of droplet actuation,splitting and particles manipulation using a cross scale digital microfluidics prototype

• Main Author: Hassan, Md. Fuhad
• Language: English
• Published: University of British Columbia 2013
• Online Access: http://hdl.handle.net/2429/44244

Digital microfluidics (DMF) system or device can be used as a significant and useful tool for chemical, bio-chemical and bio-medical applications because of its capability to perform basic fluidic functions and sequential chemical reactions on miniscule (nanolitre) droplets with better precision and accuracy. Application of sufficient electric potential in a sequence of electrodes manipulates the droplet in an electro wetting on dielectric (EWOD)-based DMF system. The successful implementation and the reliability of an EWOD-based DMF system depends on perfect design and fabrication of the lab-on-a-chip or DMF chip and also on the successful demonstration of basic fluidic functions including droplet actuation, splitting, mixing and separation within the DMF system. This thesis focuses on the study of the efficacy and feasibility of cost-effective fabrication of a cross-scale electrode design for EWOD-based digital microfluidics lab-on-a-chip (LOC) systems. The intended microfluidic operations on this LOC include droplet actuation, splitting and particles manipulation (separation). The main features of the proposed cross-scale digital microfluidics prototype include one or more reservoirs, a linear array of square and rectangular electrodes forming the channel for liquid droplets, and a separation site consisting of multiple strip electrodes known as the high density electrodes or the strip electrodes. The fabrication process introduces newer dielectric materials (Cyanoethyl Pullulan (CEP) and S1813 positive photoresist) which result in a simpler fabrication of the proposed DMF prototype. The newer dielectric materials also enhance the functional quality by reducing the required voltage for droplet actuation and increasing the breakdown voltage. Successful droplet splitting has been demonstrated on the proposed cross-scale DMF prototype, and droplet actuation is investigated as the precursor for any operations including splitting. Dielectrophoresis (DEP) is applied to the strip electrodes of the proposed prototype to enhance the movement of particles. The non-uniform electric field generated by the DEP controls the motion of the particles. The strip electrodes are used to enhance the particle trapping and one-side (within the droplet) movement of the particles. A flawless cross-scale digital microfluidics prototype is built by optimizing the fabrication recipe.