Appropriate control of substrate surface properties prior to inkjet printing could be employed to improve the printing quality of fine resolution structures. In this paper, novel methods to fabricate patterned surfaces with a combination of hydrophilic and hydrophobic properties are investigated. The results of inkjet printing of PEDOT/PSS conductive ink on these modified surfaces are presented. Selective wetting was achieved via a two-step hydrophilic-hydrophobic coating of 3-aminopropyl trimethoxysilane (APTMS) and 3M electronic grade chemical respectively on PET surfaces; this was followed by a selective hydrophilic treatment (either atmospheric O2/Ar plasma or UV/ozone surface treatment) with the aid of a Nickel stencil. Hydrophobic regions with water contact angle (WCA) of 105° and superhydrophilic regions with WCA <5° can be achieved on a single surface. During inkjet printing of the treated surfaces, PEDOT/PSS ink spread spontaneously along the hydrophilic areas while avoiding the hydrophobic regions. Fine features smaller than the inkjet droplet size (approximately 55 μm in diameter) can be successfully printed on the patterned surface with high wettability contrast.

In conventional injection molding, the molten polymer in the filling stage is generally assumed to be incompressible. However, this assumption may not be valid in micro-injection molding, since high injection pressure is normally required to avoid short shots. This paper presents both numerical and experimental investigations on the effects of polymer melt compressibility on mold filling into a micro-thickness impression. The study was conducted on six different part thicknesses ranging from 920 to 370 µm. A high-flow COC TOPAS 5013L-10 polymer was chosen as the TOPAS family has recently attracted significant interest for its use in microfluidic applications. A combined finite element/finite difference/control volume approach was adopted to simulate the compressible flow. The shear viscosity of a polymer melt was characterized by the Cross-WLF model, while the melt compressibility was modeled with a double-domain Tait equation. The results obtained indicated that the compressibility of the polymer melt has significant effects on impression pressure and density distribution in the fully filled part with thickness smaller than 620 µm and that the effects become more pronounced with a decrease in part thickness.

No abstract

Life of bacteria is governed by the physical dimensions of life in microscales, which is dominated by fast diffusion and flow at low Reynolds numbers. Microbial biofilms are structurally and functionally heterogeneous and their development is suggested to be interactively related to their microenvironments. In this study, we were guided by the challenging requirements of precise tools and engineered procedures to achieve reproducible experiments at high spatial and temporal resolutions. Here, we developed a robust precise engineering approach allowing for the quantification of real-time, high-content imaging of biofilm behaviour under well-controlled flow conditions. Through the merging of engineering and microbial ecology, we present a rigorous methodology to quantify biofilm development at resolutions of single micrometre and single minute, using a newly developed flow cell. We designed and fabricated a high-precision flow cell to create defined and reproducible flow conditions. We applied high-content confocal laser scanning microscopy and developed image quantification using a model biofilm of a defined opportunistic strain, Pseudomonas putida OUS82. We observed complex patterns in the early events of biofilm formation, which were followed by total dispersal. These patterns were closely related to the flow conditions. These biofilm behavioural phenomena were found to be highly reproducible, despite the heterogeneous nature of biofilm.