Electrical actuation of dielectric droplets by negative liquid dielectrophoresis.

This paper presents an electrical actuation scheme of dielectric droplet by negative liquid dielectrophoresis. A general model of lumped parameter electromechanics for evaluating the electromechanical force acting on the droplets is established. The model reveals the influence of actuation voltage, device geometry, and dielectric parameter on the actuation force for both conductive and dielectric medium. Using this model, we compare the actuation forces for four liquid combinations in the parallel-plate geometry and predict the low voltage actuation of dielectric droplets by negative dielectrophoresis. Parallel experimental results demonstrate such electric actuation of dielectric droplets, including droplet transport, splitting, merging, and dispending. All these dielectric droplet manipulations are achieved at voltages < 100 Vrms . The frequency dependence of droplet actuation velocity in aqueous solution is discussed and the existence of surfactant molecules is believed to play an important role by realigning with the AC electric field. Finally, we present coplanar manipulation of oil and water droplets and formation of oil-in-water emulsion droplet by applying the same low voltage.

Prehospital Whole Blood in SOF: Current Use and Future Directions.

The US Joint Trauma System (JTS) recommends stored whole blood (SWB) as the preferred product for prehospital resuscitation of battlefield casualties in both their Tactical Combat Casualty Care (TCCC) guidelines and their clinical practice guidelines (CPGs). Clinical data from nearly 2 decades of war during Operation Iraqi Freedom (OIF) and Operation Enduring Freedom (OEF) suggest that whole blood (WB) is safe, effective, and far superior to crystalloid and colloid resuscitation fluids. The JTS CPG for whole blood transfusion reflects the most recent clinical evidence but poses unique challenges for execution by Special Operations Forces (SOF) operating in austere environments. Given the limited shelf-life of 35 days, WB requires a constant steady pool of donors. Additionally, the cold-chain requirement for storage poses challenges for SOF on long missions without access to blood refrigerators. SOF operating in less-developed theaters face additional logistical challenges. To mitigate the challenges of WB delivery, US SOF have implemented various protocols to ensure optimal donor pool, awareness/education among medics and specialized equipment for tactical methods of blood-carry and delivery. In general, steps taken include the following: (1) Prior to deployment, soldiers are screened for blood type and titers in order to establish a large donor pool. Support soldiers have been found to be particularly beneficial donors as they typically are in closer proximity to the blood support detachment. (2) In units that operate in smaller teams, such as ODAs, medics are outfitted with "blood kits" to carry blood on missions for point of injury transfusion. In units with larger teams, LTOWB donors are identified on missions and deliver fresh WB in the event of casualties. (3) Medics receive a WB transfusion refresher tabletop exercise and review after action reviews from previous rotations. Additionally, prehospital WB delivery is a required component of scenario-based premission training. The expectation is that medics will administer WB on missions when tactically feasible. Using the prolonged field care framework (ruck, truck, house) as a template, medics now use different methods to store and transport the SWB depending on phase. Medic "truck" and "house" kits include the Dometic CFX™ powered coolers that run on AC, DC, or solar power and allow for constant temperature monitoring. When on foot, medics have been outfitted with tactical blood coolers including the Pelican Biomedical Medic 4™ or Combat Medical Blood Box™ along with a Belmont Buddy-Lite™ intravenous (IV) infusion warmer and IV administration kit with standard micron filter. Presently, SOF medics have the donor support, logistical framework, training, and equipment to deliver WB at the point of injury. However, widespread implementation will require expanded distribution and standardization of "blood kits." Additionally, SOF medical planners must put greater emphasis on education and the importance of WB over crystalloids or colloids-as many medics continue to carry only these products out of convenience. As SOF strive to establish tactics, techniques, and procedures (TTPs) and streamline prehospital WB delivery, we must constantly reassess and refine our procedures, incorporate the latest evidence and technology, and adapt to an evolving battlefield.

Moving droplets between closed and open microfluidic systems.

In electric-field-mediated droplet microfluidics, there are two distinct architectures - closed systems using parallel-plate electrodes and open systems using coplanar electrodes fabricated on an open substrate. An architecture combining both closed and open systems on a chip would facilitate many of the chemical and biological processes now envisioned for the laboratory on a chip. To accomplish such an integration requires a means to move droplets back and forth between the two. This paper presents an investigation of the requirements for such manipulation of both water and oil droplets. The required wetting conditions for a droplet to cross the open/closed boundary is revealed by a force balance analysis and predictions of this model are compared to experimental results. Water droplets can be moved between closed and open systems by electrowetting actuation; droplet detachment from the upper plate is facilitated by the use of beveled edge. The force model predicts that driving an oil droplet from a closed to an open structure requires an oleophobic surface. This prediction has been tested and confirmed using <100> silicon wafers made oleophobic by re-entrant microstructures etched into the surface.

Statistical algorithms for ontology-based annotation of scientific literature.

BACKGROUND: Ontologies encode relationships within a domain in robust data structures that can be used to annotate data objects, including scientific papers, in ways that ease tasks such as search and meta-analysis. However, the annotation process requires significant time and effort when performed by humans. Text mining algorithms can facilitate this process, but they render an analysis mainly based upon keyword, synonym and semantic matching. They do not leverage information embedded in an ontology's structure. METHODS: We present a probabilistic framework that facilitates the automatic annotation of literature by indirectly modeling the restrictions among the different classes in the ontology. Our research focuses on annotating human functional neuroimaging literature within the Cognitive Paradigm Ontology (CogPO). We use an approach that combines the stochastic simplicity of naïve Bayes with the formal transparency of decision trees. Our data structure is easily modifiable to reflect changing domain knowledge. RESULTS: We compare our results across naïve Bayes, Bayesian Decision Trees, and Constrained Decision Tree classifiers that keep a human expert in the loop, in terms of the quality measure of the F1-mirco score. CONCLUSIONS: Unlike traditional text mining algorithms, our framework can model the knowledge encoded by the dependencies in an ontology, albeit indirectly. We successfully exploit the fact that CogPO has explicitly stated restrictions, and implicit dependencies in the form of patterns in the expert curated annotations.

Automated annotation of functional imaging experiments via multi-label classification.

Identifying the experimental methods in human neuroimaging papers is important for grouping meaningfully similar experiments for meta-analyses. Currently, this can only be done by human readers. We present the performance of common machine learning (text mining) methods applied to the problem of automatically classifying or labeling this literature. Labeling terms are from the Cognitive Paradigm Ontology (CogPO), the text corpora are abstracts of published functional neuroimaging papers, and the methods use the performance of a human expert as training data. We aim to replicate the expert's annotation of multiple labels per abstract identifying the experimental stimuli, cognitive paradigms, response types, and other relevant dimensions of the experiments. We use several standard machine learning methods: naive Bayes (NB), k-nearest neighbor, and support vector machines (specifically SMO or sequential minimal optimization). Exact match performance ranged from only 15% in the worst cases to 78% in the best cases. NB methods combined with binary relevance transformations performed strongly and were robust to overfitting. This collection of results demonstrates what can be achieved with off-the-shelf software components and little to no pre-processing of raw text.

Polymerization of electric field-centered double emulsion droplets to create polyacrylate shells.

Porous and hollow particles are widely used in pharmaceuticals, as solid phases for chromatography, as catalyst supports, in bioanalytical assays and medical diagnostics, and in many other applications. By controlling size, shape, and chemistry, it is possible to tune the physical and chemical properties of the particles. In some applications of millimeter-scale hollow shells, such as in high energy density physics, controlling the shell thickness uniformity (concentricity) and roundness (sphericity) becomes particularly important. In this work, we demonstrate the feasibility of using electric field-driven droplet centering to form highly spherical and concentric polymerizable double emulsion (DE) droplets that can be subsequently photopolymerized into polymer shells. Specifically, when placed under the influence of an ∼6 × 10(4) V(rms)/m field at 20 MHz, DE droplets, consisting of silicone oil as the inner droplet and tripropylene glycol diacrylate with a photoinitiator in N,N-dimethylacetamide as the outer droplet, suspended in ambient silicone oil, were found to undergo electric field-driven centering into droplets with ≥98% sphericity and ∼98% concentricity. The centered DE droplets were photopolymerized in the presence of the electric field. The high degrees of sphericity and concentricity were maintained in the polymerized particles. The poly(propylene glycol diacrylate) capsules are just within the sphericity requirements needed for inertial confinement fusion experiments. They were slightly outside the concentricity requirement. These results suggest that electric field-driven centering and polymerization of double emulsions could be very useful for synthesizing hollow polymer particles for applications in high energy density physics experiments and other applications of concentric polymer shells.

Rapid enrichment of biomolecules using simultaneous liquid and particulate dielectrophoresis.

Here we show that dielectrophoretic (DEP) liquid actuation can be used to dispense arrays of nanoliter-sized droplets loaded with biomolecules. Size-based enrichment of these biomolecules occurs rapidly and simultaneously with the droplet dispensing. The physical mechanism responsible for the effect is the positive DEP force directed toward the electrodes that is imposed by the non-uniform electric field during the very rapid DEP actuated flow before droplet formation. Experiments conducted with a suspension of lambda DNA (molecular weight: 31.5 x 10(3) kDa) and lectin protein (120 kDa) containing identical molar concentration shows separation of DNA and protein within the nanolitre sized droplets formed along the electrode. The density ratio of protein to DNA varies smoothly from 1 : 1 in the parent droplet to approximately 3 : 1, favoring the smaller sized protein in the daughter droplet dispensed furthest from the parent droplet, approximately 2.4 mm from the parent droplet. Experiments conducted with binary protein solutions containing identical molar concentrations of bovine serum albumin (66 kDa) and fibrinogen (340 kDa) reveal that enrichment is enhanced as the length of the electrodes is increased. The density ratio of BSA to fibrinogen varied from 1 : 1 in the parent droplet to approximately 1.97 : 1 at the last (tenth) droplet, located approximately 4.2 mm from the parent droplet. The entire process, consisting of droplet dispensing and particle separation, occurs in less than one second.

DEP actuated nanoliter droplet dispensing using feedback control.

Dielectrophoretic (DEP) droplet dispensing using dielectric-coated coplanar electrode structures provides an ideal platform for testing smart control systems for high-speed microfluidic devices. Open-loop control of DEP droplet dispensing is not sufficiently robust for precision droplet dispensing because unavoidable surface property variations of the substrates and other parameters such as liquid viscosity introduce uncertainty in the motion. Closed-loop systems employing distributed optical sensors and feedback provide flexibility, sensitivity, and reliability. In this new scheme, an array of distributed optical sensors detects fluid motion and, through a programmable control module, triggers application of AC voltage bursts of appropriate magnitude, duration, and frequency to control liquid motion and droplet formation. Reconfiguring the module connections and reprogramming the control module permits testing of a variety of control strategies.