Rigid organic molds for nanoimprint lithography by replica molding of high glass transition temperature polymers

The glass transition of polycarbonate resins of high softness temperature is exploited to realize rigid polymeric replicas of master patterns, with no need for antisticking layers and applied pressure. Such replicas enable the transfer of patterns onto polymers having a lower glass-transition temperature by nanoimprint lithography. As a demonstration, we show the pattern transfer onto poly(methylmethacrylate), which demonstrates good fidelity and remarkable simplicity of the process

Superhydrophobicity Due to the Hierarchical Scale Roughness of PDMS Surfaces

Wettability control has been widely investigated in the last decades for technological applications such as microfluidic devices and self-cleaning surfaces by modifying both the chemical composition and the geometric structure of the surfaces. Inspired by the typical morphology of superhydrophobic leaves (such as lotus leaves), we have developed a dual-scale roughness, micro- and nanosized, on polydimethylsiloxane (PDMS) surfaces. By combining different geometric parameters and plasma treatment conditions, the structures were controlled hierarchically, at different independent length scales. Both the microsized replicated pillars and the nanosized etched posts tuned the wettability of the PDMS surfaces in a very simple way, up to contact angles of 170°. Furthermore, changes in the influence of micro- and nanoscale geometrical structures were investigated. Hysteresis and contact angles of water droplets are evaluated as a combined effect of micropillars and a superimposed roughness, resulting in high advan..

Positive Negative Arrays of Organic Light Emitting Diodes by a Surface Tension driven approach

A surface-tension-driven technique to pattern molecular arrays of organic light-emitting diodes by using a metallic grid to induce the geometrical confinement was presented. The technique enables the controlled replication of the micrometer-scale template, allowing the fabrication of arrays of OLED pixels of a well-defined geometry. The principle of this approach is the controlled dewetting of the molecular compounds in the feature of the template, allowing to realize either negative or positive patterns. The molecular TPD-patterned layer was realized by taking advantage of the combination of both liquid instability, following the dewetting phenomena, and geometrical confinement, induced by a template mes

Engineering transfer of micro- and nanometer-scale features by surface energy modification.

Micropatterning of surfaces is gaining importance in various applications ranging from biosensors to microfluidic and lab-on-a-chip devices, where the control of the surface chemistry is of great importance for the application. In this paper, we introduce a patterning technique of topographical features, which is applicable on different substrates by modifying their surface energy. The textured surface is obtained via polydimethylsiloxane (PDMS) transfer, and the topographical parameters can be systematically tailored by selective treatment with oxygen plasma of either the PDMS stamp, the substrate, or both. Our approach is an alternative technique to create micro- and nanopatterns of various height and shape over a large area on different substrates. The possibility to control cell behavior on different surfaces tailored with this microtransfer patterning approach was also evaluated. The cell culture on patterned surfaces showed the possibility of modulating cell adhesion. Our method is based on simple transfer of silicone elastomeric patterns to the surface, and therefore, it is very simple and fast compared to other complex techniques. These observations could have implications for tissue-scaffold engineering science in areas such as microfluidic devices and control of cell adhesion

Hybrid Light-Emitting Diodes from Microcontact-Printing Double-Transfer of Colloidal Semiconductor CdSe/ZnS Quantum Dots onto Organic Layers

We have developed a totally dry technique for the deposition of colloidal semiconductor nanocrystals on organic substrates. This approach is fully compatible with current organic LED technology. It appears that the slow evaporation of drop-cast QD films is critical for the success of the transfer process. This novel approach has been utilized to fabricate a hybrid organic–inorganic red LE

Correction: Sustained anti-BCR–ABL activity with pH responsive imatinib mesylate loaded PCL nanoparticles in CML cells

</p

Influence of variable substrate geometry on wettability and cellular responses

In this report, we evaluate the impact of a systematic change to the extracellular environment on cell morphology and functionality by combining the inherent properties of biocompatible polymers such as polydimethylsiloxane and polycaprolactone with a specific surface response. By microstructuring pillars and pits on the substrates, varying spacing and height of the structures, we investigate the role of topography in fibroblast cell adhesion and viability. The change of wetting behaviour was tailored and evaluated in terms of contact angle measurements. It was shown that the range of micro-scale physical cues at the interface between the cells and the surrounding environment affects cell shape and migrations, indicating a tendency to respond differently to higher features of the micro-scale. We found that surface topography seems dominant over material wettability, fibroblasts responded to variations in topography by altering morphology and migrating along the direction of spacing among the features biased by the height of structures and not by the material. It is therefore possible to selectively influence either cell adhesion or morphology by choosing adequate topography of the surface. This work can impact in the design of biomaterials and can be applied to implanted biomedical devices, tissue engineering scaffolds and lab on chip devices

Influence of electrotaxis on cell behaviour

Understanding the mechanism of cell migration and interaction with the microenvironment is not only of critical significance to the function and biology of cells, but also has extreme relevance and impact on physiological processes and diseases such as morphogenesis, wound healing, neuron guidance, and cancer metastasis. External guidance factors such as topography and physical cues of the microenvironment promote directional migration and can target specific changes in cell motility and signalling mechanisms. Recent studies have shown that cells can directionally respond to applied electric fields (EFs), in both in vitro and in vivo settings, a phenomenon called electrotaxis. However, the exact cellular mechanisms for sensing electrical signals are still not fully well understood, and it is thus far unknown how cells recognize and respond to electric fields, although some studies have suggested that electromigration of some cell surface receptors and ion channels in cells could be involved. Applied electric fields may have a potential clinical role in guiding cell migration and present a more precise manageability to change the magnitude and direction of the electric field than most other guidance cues such as chemical cues. Here we present a review of recent studies used for studying electrotaxis to point out similarities, identify points of disagreement, and stimulate new directions for investigation. Insights into the mechanisms by which applied EFs direct cell migration, morphological change and development will enable current and future therapeutic applications to be optimized

Micropatterned polyelectrolyte nanofilms promote alignment and myogenic differentiation of C2C12 cells in standard growth media

Alignment of skeletal myoblasts is considered a critical step during myotube formation. The C2C12 cell line is frequently used as a model of skeletal muscle differentiation that can be induced by lowering the serum concentration in standard culture flasks. In order to mimic the striated architectures of skeletal muscles in vitro, micro-patterning techniques and surface engineering have been proven as useful approaches for promoting elongation and alignment of C2C12 myoblasts, thereby enhancing the outgrowth of multi-nucleated myotubes upon switching from growth media (GM) to differentiative media (DM). Herein, a layer-by-layer (LbL) polyelectrolyte multilayer deposition was combined with a micro-molding in capillaries (MIMIC) method to simultaneously provide biochemical and geometrical instructive cues that induced the formation of tightly apposed and parallel arrays of differentiating myotubes from C2C12 cells maintained in GM media for 15 days. This study focuses on two different types of patterned/self-assembled nanofilms based on alternated layers of poly (allylamine hydrochloride) (PAH)/poly(sodium 4-styrene-sulfonate) (PSS) as biocompatible but not biodegradable polymeric structures, or poly-L-arginine sulfate salt (pARG)/dextran sulfate sodium salt (DXS) as both biocompatible and biodegradable surfaces. The influence of these microstructures as well as of the nanofilm composition on C2C12 skeletal muscle cells' differentiation and viability was evaluated and quantified, pointing to give a reference for skeletal muscle regenerative potential in culture conditions that do not promote it. At this regard, our results validate PEM microstructured devices, to a greater extent for (PAH/PSS)5-coated microgrooves, as biocompatible and innovative tools for tissue engineering applications and molecular dissection of events controlling C2C12 skeletal muscle regeneration without switching to their optimal differentiative culture media in vitro. Biotechnol. Bioeng. 2013; 110: 586596. (c) 2012 Wiley Periodicals, Inc