@article{kuncicky_velev_2008, title={Surface-guided templating of particle assemblies inside drying sessile droplets}, volume={24}, ISSN={["0743-7463"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-40449101377&partnerID=MN8TOARS}, DOI={10.1021/la702129b}, abstractNote={The particles suspended inside evaporating sessile droplets can be assembled into microscopic objects with long-ranged ordered structure. The air-water droplet interface guides the assembly and determines the shape of the resulting micropatches. We report the results of a systematic study of the mechanism of interface-templated assembly on substrates of controlled contact angle. The kinetics of drying were examined by measurements of droplet profiles, and it was found that the rate matched diffusion-limited evaporation well. The shape of the droplets and of the resulting assemblies was correlated to the dynamics of the receding contact line. The effects of major parameters controlling the process, including contact angle, particle concentration, and electrolyte, were investigated in detail. A variety of micropatch shapes were observed and categorized within the parameter space. The in-depth characterization of the process allowed the optimization of the assembly and the formulation of protocols for the deposition of nanostructured patches of different diameter, thickness, and shape.}, number={4}, journal={LANGMUIR}, author={Kuncicky, Daniel M. and Velev, Orlin D.}, year={2008}, month={Feb}, pages={1371–1380} }
 @article{prevo_kuncicky_velev_2007, title={Engineered deposition of coatings from nano- and micro-particles: A brief review of convective assembly at high volume fraction}, volume={311}, ISSN={["1873-4359"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-35648966536&partnerID=MN8TOARS}, DOI={10.1016/j.colsurfa.2007.08.030}, abstractNote={In this paper, we review the state of the art of a simple, easily controlled convective assembly technique for rapid deposition of structured micro- and nano-particle coatings. The advantages afforded by this method are improved process efficiency and reduced material consumption relative to standard dipcoating techniques. Structured coatings larger than a few square centimeters are deposited in minutes from aqueous suspension volumes of approximately 10–20 μl. The governing mechanism of particle deposition is convective assembly at high volume fractions. Our research with monodisperse polystyrene latex showed that a volumetric flux balance incorporating the evaporating solvent and assembling particle fluxes can accurately relate the deposition process parameters to the coating structure and properties. Operational ’phase’ diagrams were constructed that demonstrate good correspondence between coating thickness and structure to the operational parameters of the coatings process predicted on the basis of the material balance model. These ’phase’ diagrams may be instrumental in turning the colloidal deposition into a usable and scaleable technology. This deposition technique can be applied to a variety of colloidal systems, including the fabrication of conductive and antireflective coatings, surface-enhancing Raman scattering (SERS) substrates, and lithographic masks.}, number={1-3}, journal={COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS}, author={Prevo, Brian G. and Kuncicky, Daniel M. and Velev, Orlin D.}, year={2007}, month={Dec}, pages={2–10} }
 @article{kuncicky_bose_costa_velev_2007, title={Sessile droplet templating of miniature porous hemispheres from colloid crystals}, volume={19}, ISSN={["1520-5002"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33846892531&partnerID=MN8TOARS}, DOI={10.1021/cm062217j}, abstractNote={A technique for fabrication of porous hemispherical particle assemblies by drying small droplets on silanized surfaces is presented. The resulting uniform, flat-end porous microidenters are being used in biological research.}, number={2}, journal={CHEMISTRY OF MATERIALS}, author={Kuncicky, Daniel M. and Bose, Kunal and Costa, Kevin D. and Velev, Orlin D.}, year={2007}, month={Jan}, pages={141–143} }
 @article{kuncicky_naik_velev_2006, title={Rapid deposition and long-range alignment of nanocoatings and arrays of electrically conductive wires from tobacco mosaic virus}, volume={2}, ISSN={["1613-6829"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-33751245136&partnerID=MN8TOARS}, DOI={10.1002/smll.200600399}, abstractNote={Nanostructured and mesoscopically ordered architectures based on biomaterial templates may be used in making integrated mechanical, optical, and electronic devices. A scheme for fabricating such devices will likely employ patterned functional biomaterials, which are used as scaffolds for the directed growth of inorganic materials. Tobacco mosaic virus (TMV) and M13 bacteriophage are particularly interesting as bioscaffolds owing to the combined chemical functionality of the virus protein coat, low size polydispersity, liquid-crystalline organization, and length scales that bridge the gap between traditional bottom-up and top-down fabrication schemes. Recent advances in the biomimetic synthesis of inorganic materials by using genetically engineered viruses and proteins have opened the door to new organic–inorganic composites containing metals, silica, and semiconductors. The major challenge in using such bioscaffolds in technology lies in developing new surface-patterning techniques that are controllable, reproducible, and efficient. We report here a versatile technique for rapidly assembling large-scale nanocoatings and ordered fibers from tobacco mosaic virus and converting them into electrically functional structures. The nanofilms were deposited by pulling, with a constant rate, a meniscus containing the virus suspension. Current molecular and colloidal self-assembly techniques for patterning surfaces with functional biomaterials include Langmuir–Blodgett lithography, templating in sessile droplets with imposed shear, self-assembly driven by dewetting or chemoselective interactions on micropatterned surfaces, and electrostatic layer-by-layer assembly. The technique that we report here uses an alternative flow assembly technique for organizing and aligning TMV into fibers and wires on surfaces. These films were of controlled thickness, structure, and long-range virus orientation, properties achieved by a combination of shear and dewetting. The density and branching of the virus wires were controlled by varying the substrate wettability and the meniscus withdrawal speed. The virus fibers were converted into anisotropically conductive arrays of wires of lengths of multiple centimeters by conjugation of gold nanoparticles followed by silver-metal deposition. TMV is a rod-shaped virus (300 nm in length and 18 nm in diameter), which forms lyotropic liquid crystals. Above a certain critical concentration, suspensions of TMV undergo an isotropic–nematic (I–N) transition. Although the suspensions used here are well below the concentration required for the I–N transition, the formation of phase-separated aggregates can be observed in drying droplets. When droplets of this TMV suspension on a surface were allowed to evaporate, they exhibited alignment of linear virus aggregates normal to the three-phase contact line (Figure 1b). As the meniscus receded, these aggregates were deposited as fibers and strands onto the substrate. Although deposition from sessile drops may be useful for fabricating multiplexed arrays of TMV dots and patches, we want to be able to exert operational control over the fiber orientation for the long-range alignment of nanocoatings and wires. This could be achieved by pulling a meniscus containing the virus suspension over a substrate by using an apparatus for conACHTUNGTRENNUNGtrolled colloidal deposition similar to the one developed by us for convective nanoparticle assembly (shown schematically in Figure 1a). However, in contrast to the results of our earlier studies on particle crystallization with this experimental setup, the evaporation at the air–liquid interface near the three-phase contact line (leading to convective assembly) was found to have a minimal effect on the assembly of the TMV into strands and fibers. The organization of TMV in the experiment could be explained by shearACHTUNGTRENNUNG-induced virus alignment working in conjunction with dewetting-driven assembly at the three-phase contact line. We characterized the dependence of the TMV fiber size, packing density, and alignment on how well the aqueous suspension wetted the substrate. Dense arrays of narrow fibers were deposited when a hydrophilic glass substrate (contact angle <48) was used (Figure 1d,e). The diameter of the strands at low concentration (5 mgmL , Figure 1d) was typically between four and eight viruses. Deposition of fibers at a higher concentration (40 mgmL , Figure 1e) effectively increased the fiber diameter and at the same time decreased the spacing between individual fibers. The parallel linear fibers in both cases were contiguous and span the entire length of the substrate. Coatings with a contiguous structure over lengths of 2–4 centimeters were fabricated. On hydrophilic substrates, atomic force microscopy (AFM) [*] D. M. Kuncicky, Prof. O. D. Velev Department of Chemical and Biomolecular Engineering North Carolina State University Raleigh, NC 27695 (USA) Fax: (+1)919-515-3465 E-mail: odvelev@unity.ncsu.edu}, number={12}, journal={SMALL}, author={Kuncicky, Daniel M. and Naik, Rajesh R. and Velev, Orlin D.}, year={2006}, month={Dec}, pages={1462–1466} }
 @article{kuncicky_christesen_velev_2005, title={Role of the micro- and nanostructure in the performance of surface-enhanced Raman scattering substrates assembled from gold nanoparticles}, volume={59}, ISSN={["1943-3530"]}, DOI={10.1366/0003702053641559}, abstractNote={ Highly active and stable substrates for surface-enhanced Raman scattering (SERS) can be fabricated by using colloidal crystals to template gold nanoparticles into structured porous films. The structure-dependent performance of these SERS substrates was systematically characterized with cyanide in continuous flow microfluidic chambers. A matrix of experiments was designed to isolate the SERS contributions arising from nano- and microscale porosity, long-range ordering of the micropores, and the thickness of the nanoparticle layer. The SERS results were compared to the substrate structure observed by scanning electron microscopy (SEM) and optical microscopy to correlate substrate structure to SERS performance. The Raman peak intensity was consistently highest for nanoporous substrates with three-dimensionally ordered micropores, and decreases if the micropores are not ordered or not templated. Removing the nanoscale porosity by fusion of the nanoparticles (without removing the large micropores) leads to a drastic plunge in substrate performance. The peak intensity does not strongly correlate to the thickness of the nanoparticle films. The results make possible the efficient controlled fabrication of stable, reproducible, and highly active substrates for SERS based chemical sensors with continuous sampling. }, number={4}, journal={APPLIED SPECTROSCOPY}, author={Kuncicky, DM and Christesen, SD and Velev, OD}, year={2005}, month={Apr}, pages={401–409} }