Kenneth R. Pohl

High-efficiency magnetic particle focusing using dielectrophoresis and magnetophoresis in a microfluidic device

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.

A comprehensive approach to decipher biological computation to achieve next generation high-performance exascale computing.

The human brain (volume=1200cm3) consumes 20W and is capable of performing>10%5E16 operations/s. Current supercomputer technology has reached 1015 operations/s, yet it requires 1500m%5E3 and 3MW, giving the brain a 10%5E12 advantage in operations/s/W/cm%5E3. Thus, to reach exascale computation, two achievements are required: 1) improved understanding of computation in biological tissue, and 2) a paradigm shift towards neuromorphic computing where hardware circuits mimic properties of neural tissue. To address 1), we will interrogate corticostriatal networks in mouse brain tissue slices, specifically with regard to their frequency filtering capabilities as a function of input stimulus. To address 2), we will instantiate biological computing characteristics such as multi-bit storage into hardware devices with future computational and memory applications. Resistive memory devices will be modeled, designed, and fabricated in the MESA facility in consultation with our internal and external collaborators.

Packaging Dissimilar Materials for Microfluidic Applications

In this paper we address the problem of assembling several different microfluidic devices, often made from different materials, into a hybrid packaged system. The focus will be on integration of silicon microfluidic die into larger hybrid systems. Details of three different approaches are presented: 1) a plastic flow manifold with tape die attach, 2) multiple capillary die insertion utilizing PDMS (Polydimethylsiloxane – silicone adhesive) for sealing and structural support, and 3) die attachment to a glass flow manifold utilizing anodic bonding. The unique tools required for each of these three techniques will be described. Sealed microfluidic connections (>10 ATM pressure) between silicon microfluidic chips (die) and flow manifolds are demonstrated.Copyright

Quantification of false positive reduction in nucleic acid purification on hemorrhagic fever DNA.

Columbia University has developed a sensitive highly multiplexed system for genetic identification of nucleic acid targets. The primary obstacle to implementing this technology is the high rate of false positives due to high levels of unbound reporters that remain within the system after hybridization. The ability to distinguish between free reporters and reporters bound to targets limits the use of this technology. We previously demonstrated a new electrokinetic method for binary separation of kb pair long DNA molecules and oligonucleotides. The purpose of this project 99864 is to take these previous demonstrations and further develop the technique and hardware for field use. Specifically, our objective was to implement separation in a heterogeneous sample (containing target DNA and background oligo), to perform the separation in a flow-based device, and to develop all of the components necessary for field testing a breadboard prototype system.

Packaging Hand-Held MEMS — MinIMEs (Miniature Integration of MEMS/Electronics)

In this paper we present two complete MEMS microsystems, one optical and one microfluidic, with associated packaging, light sources, signal modulation, optics, fluid connections and flow control. These are fully functional hand held devices and as such demonstrate a means of freeing the MEMS device from the laboratory environment and inserting it into the field. This highly integrated packaging concept can be applied to a wide range of surface micromachined MEMS, and probably other non-surface micromachined MEMS devices, which are generally easier to package.Copyright