Structurally modified superhydrophobic surfaces have become particularly desirable as stable antibacterial surfaces. Because their self-cleaning and water resistant properties prohibit bacteria growth, structurally modified superhydrophobic surfaces obviate bacterial resistance common with chemical agents, and therefore a robust and stable means to prevent bacteria growth is possible. In this study, we present a rapid fabrication method for creating such superhydrophobic surfaces in consumer hard plastic materials with resulting antibacterial effects. To replace complex fabrication materials and techniques, the initial mold is made with commodity shrink-wrap film and is compatible with large plastic roll-to-roll manufacturing and scale-up techniques. This method involves a purely structural modification free of chemical additives leading to its inherent consistency over time and successive recasting from the same molds. Finally, antibacterial properties are demonstrated in polystyrene (PS), polycarbonate (PC), and polyethylene (PE) by demonstrating the prevention of gram-negative Escherichia coli (E. coli) bacteria growth on our structured plastic surfaces.

A biomimetic substrate for cell‐culture is fabricated by plasma treatment of a prestressed thermoplastic shrink film to create tunable multiscaled alignment “wrinkles”. Using this substrate, the functional alignment of human embryonic stem cell derived cardiomyocytes is demonstrated.

The potential of rapid, quantitative, and sensitive diagnosis has led to many innovative ‘lab on chip’ technologies for point of care diagnostic applications. Because these chips must be designed within strict cost constraints to be widely deployable, recent research in this area has produced extremely novel non-conventional micro- and nano-fabrication innovations. These advances can be leveraged for other biological assays as well, including for custom assay development and academic prototyping. The technologies reviewed here leverage extremely low-cost substrates and easily adoptable ways to pattern both structural and biological materials at high resolution in unprecedented ways. These new approaches offer the promise of more rapid prototyping with less investment in capital equipment as well as greater flexibility in design. Though still in their infancy, these technologies hold potential to improve upon the resolution, sensitivity, flexibility, and cost-savings over more traditional approaches.

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To study the role of cell-ECM interactions, microscale approaches provide the potential to perform high throughput assessment of ECM microenvironments on cellular function and phenotype. Using a microscale direct writing (MDW) technique, we characterized the generation of multicomponent ECM microarrays for cellular micropatterning, localization, and stem cell fate determination. ECMs and other biomolecules of various geometries and sizes were printed onto epoxide-modified glass substrates for evaluation of cell attachment by human endothelial cells. The endothelial cells displayed strong preferential attachment to the ECM-patterned regions and aligned their cytoskeleton along the direction of the micropatterns. We next generated ECM microarrays that contained one or more ECM compositions (namely gelatin, collagen IV, and fibronectin) and then cultured murine embryonic stem cell (ESCs) on the microarrays. The ESCs selectively attached to the micropatterned features and expressed markers associated with a pluripotent phenotype, such as E-cadherin and alkaline phosphatase, when maintained in growth media containing leukemia inhibitory factor. In the presence of soluble factors retinoic acid and bone morphogenetic protein-4, the ESCs differentiated towards ectodermal lineage on the ECM microarray with differential ECM effects. The ESCs cultured on gelatin showed significantly higher levels of pan cytokeratin expression, when compared cells cultured on collagen IV or fibronectin, suggesting that gelatin preferentially promotes ectodermal differentiation. In summary, our results demonstrate that MDW is a versatile approach to print ECMs of diverse geometries and compositions onto surfaces, and it is amenable to the generation of multicomponent ECM microarrays for stem cell fate determination.

Injection of brine with tuned composition has been shown to give improved oil recovery from carbonate rocks. Contact angle studies, spontaneous imbibition and core flood experiments have shown that wettability alteration is responsible for this process. Possible mechanisms include mineral dissolution and ion exchange, which have been investigated by zeta-potential measurements and geochemical modeling of both processes. In this study, the core scale manifestation of these mechanisms is evaluated, and a geochemical model is developed for further insight into reaction pathways. Brines of different compositions were injected into carbonate cores with no oil and the effluent was analyzed for ionic composition. Seawater, sulfate-rich seawater, and dilutions of seawater were tested. Two phase oil displacement core floods were performed for the same brine cases to correlate the oil recovery to the geochemistry. A mechanistic model was developed using our in-house reservoir simulator UTCHEM-IPHREEQC for the wettability alteration process. The single phase core floods with all test brines indicate retention of SO42− within the core, seen by a delay in its effluent concentration reaching the injection concentration. Na+, Ca2+, Mg2+ and Cl− ions mostly behave as tracers in the system. In oil displacement core floods, formation brine recovers 40% OOIP on average and seawater recovers an incremental 7% OOIP. Sulfate-rich seawater and dilutions of seawater increase the recovery to 65-80% OOIP in secondary and tertiary modes, requiring more than 5 PVI. SO42− ion delay is not observed in the two phase core floods. Ca2+ concentrations remain high after 5 PVI of diluted seawater, indicating a slow dissolution process in the low salinity floods. The mechanistic model results were in good agreement with the single phase coreflood experiments and oil recovery experiments. The model showed that the reduction in surface concentration of naphthenic acids was responsible for altering the wettability on the injection of modified brines.

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We present a plastic microfluidic device with integrated nanoscale magnetic traps (NSMTs) that separates magnetic from non-magnetic beads with high purity and throughput, and unprecedented enrichments. Numerical simulations indicate significantly higher localized magnetic field gradients than previously reported. We demonstrated >20 000-fold enrichment for 0.001% magnetic bead mixtures. Since we achieve high purity at all flow-rates tested, this is a robust, rapid, portable, and simple solution to sort target species from small volumes amenable for pointof-care applications. We used the NSMT in a 96 well format to extract DNA from small sample volumes for quantitative polymerase chain reaction (qPCR). V C 2013 American Institute of Physics.