Microbead dispensing and ultralow DNA hybridization detection using liquid dielectrophoresis

Chip based pathogen detection is one of the prime motivation for research in the field of microfluidics. Thus far, on-chip detection has primarily been demonstrated using closed-channel microfluidic devices, which are prone to certain limitations in terms of detection threshold and complexity of sample handling. Present day pathogen detection methods are often 'bead based assays' and their success is substantially influenced by the dispensing and manipulation capability of the utilized microfluidic technology. This work utilizes liquid dielectrophoresis (LDEP) based surface microfluidics (SMF) devices to automatically dispense ultra-low concentration of various microbead samples (different in size and functionalities) by judiciously adjusting conductivity and rheological properties of actuated carrier fluids. Control over size and concentration of dispensed beads along with further manipulation and mixing for bead based bio-assays has been successfully demonstrated. The application for the proposed rapid, ultra-low, bead-based DNA hybridization detection scheme, where 1-2 micro-beads can be manipulated in nanoliter sized aliquots for detection in range of ∼100 attomoles, is envisioned for post amplification screening assays. In conclusion, we propose that LDEP based devices can be usefully applied and serve as alternative to the conventional closed channel device for ultra-low bead based detection and screening assays.