Droplet microfluidics (DMF) refers to miniaturized liquid sample handling technology where biological/chemical samples are dispensed and further manipulated in the form of ultrafine droplets (microliter to picoliter), over micro/nano patterned surfaces. Liquid dielectrophoresis (L-DEP) based DMF technology utilizes the pondermotive DEP force, generated as a result of an applied non-uniform electric field, to manipulate aqueous biological and chemical samples. L-DEP offers a rapid and parallel droplet dispensing methodology that is not achieved by other microfluidic droplet dispensing methods. Integrated with Electrowetting/Electrostatic droplet manipulation methods, DEP based DMF devices appear as a plausible alternative to conventional bio-diagnostic equipment.

The research project implements specifically designed L-DEP DMF devices to demonstrate versatile handling of homogenous liquid samples, micro-particle suspensions, multi-layered and compartmentalized vesicular assemblies and complex bio-samples/reagents during various experimental observations. Two on-chip, bio-detection assay schemes are first illustrated using synthesized nucleic acid bio-probes. These schemes are:​ ‘bead-based’ nucleic acid hybridization detection assay and bilayer lipid membrane based nucleic acid isolation/hybridization detection assay. The on-chip, bead based bio-detection method is also implemented to demonstrate a ‘molecular beacon-on-bead’ post amplification detection assay for clinically extracted and amplified Influenza ‘C’ amplicon samples. Numerical analysis is conducted to optimize L-DEP based precision dispensing of functionalized/non-functionalized micro-beads with micro-bead diameter in the range of 1-16 micron, during the on-chip ‘bead-based assays.

In order to handle complex bio-samples such as:​ PCR mix, PCR products and reagents, without excessive sample adsorption, contamination and droplet collapsing, a comprehensive fabrication protocol was developed to generate nano-textured superhydrophobic (SH) surface topology for L-DEP device applications. The static and transient behavior of L-DEP liquid handling over the fabricated SH surface are investigated utilizing an improved lumped model and furthermore experimentally verified using specifically tailored liquid samples. Performance of the developed SH surface is analyzed during liquid actuation of TAQ DNA polymerase enzyme and PCR amplicon products from nucleic acid amplification assays of Influenza viruses. Several new electrode architectures have been designed and have undergone preliminary testing in order to facilitate further development of L-DEP based DMF microfluidic technology, leading towards a microfluidic device that can achieve sample-to-detection bio-diagnostic assays.