Alternative lithography strategies for flexible electronics

Main aim of the research has been the development of alternative lithography strategies for the fabrication of complex, flexible electronic devices. Flexible bottom-contact, bottom-gate thin-film transistors were solely patterned with UV nanoimprint lithography on poly(ethylene naphthalate) foil. Patterning and process strategies had to be developed for thermal and UV nanoimprint lithography to control the residual layer thickness and its complete removal on the temperature sensitive, mechanically and in-plane instable foils. The foil was temporarily bonded to a supporting carrier (foil-on-carrier) to reduce the bending radius and in-plane waviness of the foil, and to provide a mechanically stable platform for proper processing. Foil-on-carriers were thermally flat imprinted with nanoimprint lithography, or a flat plateau was created on the foil-on-carrier by UV nanoimprint lithography-based step-and-repeat planarization. Thin-film transistors with a channel length from 5 μm down to 250 nm were obtained and characterized. Palladium nanoparticles and self-sintering silver nanoparticles were studied as a solution-based route for fast, low-cost and room temperature patterning of metallic wires in open microchannels on flexible foils. The ease of patterning thin but very conductive silver wires from a long-term stable aqueous solution allows integration in a roll-two-roll line to pattern the metallic contacts of a flexible electronic device.\ud The here studied fabrication methods can be potentially integrated in low-cost, high-throughput roll-to-roll fabrication lines and represent in combination with a self-aligned device layout a strategy for future generations of flexible electronic devices

A Continuous-Discontinuous Approach to Simulate Heat Transfer in Fractured Media

A macroscopic framework to model heat transfer in materials and composites, subjected to physical degradation, is proposed. The framework employs the partition of unity concept and captures the change from conduction-dominated transfer in the initial continuum state to convection and radiation-dominated transfer in the damaged state. The underlying model can be directly linked to a mechanical cohesive zone model, governing the initiation and subsequent growth and coalescence of micro-cracks. The methodology proved to be applicable for quasi-static, periodic, and transient problem

On some differential-geometric aspects of the Torelli map

In this note we survey recent results on the extrinsic geometry of the Jacobian locus inside $\mathsf{A}_g$. We describe the second fundamental form of the Torelli map as a multiplication map, recall the relation between totally geodesic subvarieties and Hodge loci and survey various results related to totally geodesic subvarieties and the Jacobian locus.Comment: To appear on Boll. UMI, special volume in memory of Paolo de Bartolomei

Identification and data-driven model reduction of state-space representations of lossless and dissipative systems from noise-free data

We illustrate procedures to identify a state-space representation of a lossless- or dissipative system from a given noise-free trajectory; important special cases are passive- and bounded-real systems. Computing a rank-revealing factorization of a Gramian-like matrix constructed from the data, a state sequence can be obtained; state-space equations are then computed solving a system of linear equations. This idea is also applied to perform model reduction by obtaining a balanced realization directly from data and truncating it to obtain a reduced-order mode

X-ray spectrum estimation from transmission measurements: preliminary results

International audienceIn this study, we propose a method to estimate the polychromatic X-ray spectrum of a microtomograph by measuring transmissions through a series of phantoms with known composition and thickness. An initially lognormal spectrum is iteratively optimized in order to obtain the best fit for all measurements. The validity of the estimated X-ray spectrum is verified based on an independent phantom

Experimental and numerical cross-validation of flow in real porous media. Part 1: Experimental framework

International audienceIn this study, we present the design of a purpose-built test cell, capable of closely mimicking boundary conditions which can be routinely imposed in fluid flow simulators. The test cell permits conducting systematic studies on the influence of unresolved pore-scale wall-roughness and pore space morphology on the hydraulic conductivity: it is therefore an ideal instrument for the generation of validation datasets for the next generation numerical flow models

Supply Chain Systems Maturing Towards the Internet-of-Things: A Framework

The Internet-of-Things (IoT) concept has been gradually developing, but it is unclear how extensive this concept is adopted within the supply chain domain. We derive an architectural framework to investigate four layers of ICT deployment. This framework enables practitioners and scientist to specify a status quo on different architectural levels and to identify possibilities for further improvement. Four extensive cases are investigated with this framework. One of the important conclusions is that “IoT” like technology and applications are pioneered in research programs, but operational logistic systems in diverse organizations primarily rely on less advanced technology, organizational structures- and work forms. This work can help in identifying gaps where IoT can strengthen future applications

Impact of vegetation die-off on spatial flow patterns over a tidal marsh

Large-scale die-off of tidal marsh vegetation, caused by global change, is expected to change flow patterns over tidal wetlands, and hence to affect valuable wetland functions such as reduction of shoreline erosion, attenuation of storm surges, and sedimentation in response to sea level rise. This study quantified for the first time the effects of large-scale (4 ha) artificial vegetation removal, as proxy of die-off, on the spatial flow patterns through a tidal marsh channel and over the surrounding marsh platform. After vegetation removal, the flow velocities measured on the platform increased by a factor of 2 to 4, while the channel flow velocities decreased by almost a factor of 3. This was associated with a change in flow directions on the platform, from perpendicular to the channel edges when vegetation was present, to a tendency of more parallel flow to the channel edges when vegetation was absent. Comparison with hydrodynamic model simulations explains that the vegetation-induced friction causes both flow reduction on the vegetated platform and flow acceleration towards the non-vegetated channels. Our findings imply that large-scale vegetation die-off would not only result in decreased platform sedimentation rates, but also in sediment infilling of the channels, which together would lead to further worsening of plant growth conditions and a potentially runaway feedback to permanent vegetation loss. Citation: Temmerman, S., P. Moonen, J. Schoelynck, G. Govers, and T. J. Bouma (2012), Impact of vegetation die-off on spatial flow patterns over a tidal marsh, Geophys. Res. Lett., 39, L03406, doi: 10.1029/2011GL050502