Material patterning on substrates by manipulation of fluidic behavior

ABSTRACT Patterned materials on substrates are of great importance for a wide variety of applications. In solution-based approaches to material patterning, fluidic flow is inevitable. Here we demonstrate not only the importance of fluidic behavior but also the methodology of engineering the flow pattern to guide the material crystallization and assembly. We show by both experiment and simulation that substrate heating, which is generally used to accelerate evaporation, produces irregular complex vortexes. Instead, a top-heating–bottom-cooling (THBC) set-up offers an inverse temperature gradient and results in a single Marangoni vortex, which is desired for ordered nanomaterial patterning near the contact line. We then realize the fabrication of large-scale patterns of iodide perovskite crystals on different substrates under THBC conditions. We further demonstrate that harnessing the flow behavior is a general strategy with great feasibility to pattern various functional materials ranging from inorganic, organic, hybrid to biological categories on different substrates, presenting great potential for practical applications.

Buoyancy-Induced Convection in a Square Enclosure Discretely Heated at One Side and Cooled either at the Top or at the Bottom Using both Gases and Liquids as Working Fluids

Laminar natural convection heat and momentum transfer in fluid-filled, square enclosures partially heated at one side and cooled either at the top or at the bottom, is studied numerically. A computational code based on the SIMPLE-C algorithm is used to solve the system of the mass, momentum and energy transfer governing equations. Simulations are performed using the Rayleigh number based on the cavity width, the thermally-active fraction of the partially heated sidewall, and the Prandtl number of the working fluid, as independent variables. It is found that the top cooling is definitely more efficient than the bottom cooling. In both cooling configurations the average Nusselt number of the cavity increases as each controlling parameter is increased. On the basis of the results obtained, a set of dimensionless correlations is developed.

Genetic transformation in commercial Tasmanian cultivars of opium poppy, Papaver somniferum, and movement of transgenicpollen in the field

We report a new transformation protocol for the pharmaceutically important opium poppy, Papaver somniferum L.; the protocol allows transformation for the first time of high yielding commercial cultivars. The method involves Agrobacterium tumefaciens infection of hypocotyl explants, followed by the production of antibiotic- or herbicide-resistant embryogenic callus and the subsequent induction of somatic embryos and plants. Key elements of the improvement are the use of buffering agents to stabilise medium pH and bottom-cooling of the cultures. Transformation was verified by PCR and Southern blot hybridisation. Transcription of transgenes was confirmed by RT–PCR and product sequencing. Expression of transgenes was detected by histochemical GUS staining, phosphinothricin acetyltransferase (PAT) enzyme assays for bar and pat genes, and western analysis of transgenic sunflower seed albumin protein. Expression of various transgenes was detected in stem, leaf, seed, capsule and latex. The pat gene was demonstrated to be stably inherited to the T2 generation and to confer phosphinothricin (PPT) herbicide resistance. Most T0 plants showed normal morphology, were self-fertile and the transgenes displayed the expected Mendelian segregation. The percentage of explants producing somatic embryos that developed into plantlets able to be transplanted to soil, ranged from 6–11% in two Tasmanian cultivars.A field trial using pat transgenic plants was designed to estimate the frequency of hybridisation at various distances into buffer rows of non-transgenic poppies and to related weed species, P. somniferum spp. setigerum and P. dubium. The frequency of hybridisation to completely compatible poppy fell sharply with distance, being 2.6% at 20 cm, 2.13% at 0.5 m and falling to 0% at 2.5 and 5 m. No hybridisation could be detected to two weed species under open pollination conditions, including the compatible P. somniferum spp. setigerum, when grown as close as 20 cm, despite flowering at the same time as the transgenic plants in the presence of foraging bees.