Micro-fabrication of Carbon Structures by Pattern Miniaturization in Resorcinol-Formaldehyde Gel

A simple and novel method to fabricate and miniaturize surface and sub-surface micro-structures and micro-patterns in glassy carbon is proposed and demonstrated. An aqueous resorcinol-formaldehyde (RF) sol is employed for micro-molding of the master-pattern to be replicated, followed by controlled drying and pyrolysis of the gel to reproduce an isotropically shrunk replica in carbon. The miniaturized version of the master-pattern thus replicated in carbon is about one order of magnitude smaller than original master by repeating three times the above cycle of molding and drying. The micro-fabrication method proposed will greatly enhance the toolbox for a facile fabrication of a variety of Carbon-MEMS and C-microfluidic devices.Comment: 16 pages, 5 figure

Control of self-organized contact instability and patterning of soft elastic films

The surface of a soft elastic film becomes unstable and forms a labyrinth pattern when a rigid flat plate is brought into adhesive contact, without application of any external pressure. These isotropic undulations have a characteristic wavelength, lamda ~ 3H, where H is the film thickness. We present here technique of ordering, aligning, and modulating these micro-labyrinth structures by using a patterned stamp, by varying the stamp-film inter-surface distance, by a lateral confinement of the instability and even by a simple shear motion of a flat stamp. Many complex structures, such as an array of femto-liter beakers and doubly periodic channels, are generated from a simple stamp consisting of parallel channels. The elastic nature of the patterns allows an in-situ tuning, manipulation, and reconfiguration of the microstructures. Regardless of their precise morphology, the structures continue to have the elastic length scale, lamda ~ 3H. The structures can also be made permanent as required by UV-ozone-induced oxidation of the structures. The underlying principles of the elastic contact instability presented here have the potential to develop into a new soft lithography techniqueselastic contact lithography (ECL), allowing a simple, rapid and large area patterning of soft solids

Membrane Active Small Molecules Show Selective Broad Spectrum Antibacterial Activity with No Detectable Resistance and Eradicate Biofilms

Treating bacterial biofilms with conventional antibiotics is limited due to ineffectiveness of the drugs and higher propensity to develop bacterial resistance. Development of new classes of antibacterial therapeutics with alternative mechanisms of action has become imperative. Herein, we report the design, synthesis, and biological evaluations of novel membrane-active small molecules featuring two positive charges, four nonpeptidic amide groups, and variable hydrophobic/hydrophilic (amphiphilic) character. The biocides synthesized via a facile methodology not only displayed good antibacterial activity against wild-type bacteria but also showed high activity against various drug-resistant bacteria such as methicillin-resistant <i>Staphylococcus aureus</i> (MRSA), vancomycin-resistant <i>Enterococcus faecium</i> (VRE), and β-lactam-resistant <i>Klebsiella pneumoniae</i>. Further, these biocides not only inhibited the formation of biofilms but also disrupted the established <i>S. aureus</i> and <i>E. coli</i> biofilms. The membrane-active biocides hindered the propensity to develop bacterial resistance. Moreover, the biocides showed negligible toxicity against mammalian cells and thus bear potential to be used as therapeutic agents