We describe a novel technique that utilizes simultaneous implementation of dielectrophoresis (DEP) and magnetophoresis (MAP) to focus magnetic particles into streams for optical analysis of biological samples. This technique does not require sheath flow and utilizes a novel interdigitated electrode array chip that yields multiple streams of flowing magnetic particles in single-file columns. The MAP force placed particles in close proximity to the microelectrodes where they were subjected to a strong DEP force that generated the particle focusing effect. Particle focusing efficiency was improved using this combination DEP–MAP technique compared to DEP alone: particle stream widths were reduced ∼47% and stream width variability was reduced 80% for focused streams of 8.5 µm diameter magnetic particles. 3 µm diameter magnetic particles were strongly focused with DEP–MAP (∼4 µm wide streams with sub-µm variability in stream width) while DEP alone provided minimal focusing. Additional components of a prototype detection system were also demonstrated including an integrated magnetic pelleting component, a hand-held MHz frequency signal generator and a bench-top near-confocal microscope for optical analysis of flowing particles. Preliminary testing of a sandwich assay performed on the surface of magnetic particles showed 50 ppb detection levels of a surrogate biotoxin (ovalbumin) in a raw milk sample.

Terrorism has been called 'war in the 21st century' (Barnett). Metrics are needed to quantify changes in threat state as well as system design trade-offs that weight the time required for accurate identification against the threat detection sensitivity. We present an adaptable agent-detection-platform capable of sensing multiple threat agents (chemical, biological and nuclear) simultaneously in diverse media and a performance model of this detection platform. A performance metric 'Time-To-Identify' (TTI); the time required to identify the presence of a given target analyte is presented. Experimental results that illustrate the new technologies required by this platform are presented. The model and metric predict the detection platform's sensitivity and speed for several CONcepts of OPeration (CONOP): (1) agent detection (chemical, viral or bacterial) in a 1 ml clinical sample, (2) botulinum toxin detection in milk and (3) pathogen detection in airplane cabin air.