Isolement et caractérisation des champignons anaérobies stricts du rumen de moutons. Premiers résultats

International audienc

Electrostatic template-assisted deposition of microparticles on electrospun nanofibers: towards microstructured functional biochips for screening applications

Electrostatic Template-Assisted Deposition (ETAD) of microparticles is described as a new process to control the deposition of microparticles by electrospraying onto a substrate. It relies on the construction of an electrostatic template by electrospinning a thin layer of fibers onto a micropatterned collector. Because the fibers cannot release their charges when they are suspended over cavities of the micropatterned collector, an electrostatic template is formed with repulsive and attractive domains. This electrostatic template is then used to guide precisely the particle deposition during the electrospraying step. Microstructured bi-layer composites with a great variety of micropatterns can thus be elaborated with any kind of materials allowing the use of the ETAD process for a wide range of applications. As a proof of concept, the ETAD process was applied for the production of composite scaffolds with poly(ε-caprolactone) nanofibers covered by a micropatterned layer of hydroxyapatite. This scaffold was then embedded in a biochip containing 21 wells and used for MG-63 cell proliferation and mineralization studies, showing their possible application in the screening of the scaffold structure for tissue engineering

Using pyridal[2,1,3]thiadiazole as an acceptor unit in a low band-gap copolymer for photovoltaic applications

Abstract In this report, we explore the optoelectronic properties of a low band-gap copolymer based on the alternation of electron rich (thiophene and thienothiophene units) and electron deficient units (pyridal[2,1,3]thiadiazole (Py)). Initial density functional theory calculations point out the interest of using the Py unit to optimize the polymer frontier orbital energy levels. A high molecular weight (Mn=49kg/mol) solution-processable copolymer, based on Py, thiophene and thienothiophene units, has been synthesized successfully. From cyclic-voltammetry and UV–visible absorption measurements a relatively deep HOMO level (−5.1eV) and an optical band-gap (1.48eV) have been estimated. Charge transport both in horizontal and vertical directions were extracted from field-effect transistors and space charge limited current diodes, respectively, and led to a relatively high in-plane hole mobility in pure polymer films (0.7×10−2cm2V−1s−1). GIWAXS results showed almost identical in-plane lamellar morphologies, with similar average size and orientation of the polymer crystalline domains in both, pure polymer films and polymer:fullerene blends. Also, the gate-voltage dependence of the field-effect mobility revealed that the energy disorder in the polymer domains was not altered by the introduction of fullerenes. The nevertheless significantly higher out-of-plane hole mobility in blends, in comparison to pure polymer films, was attributed to the minor amorphous polymer phase, presumably localized close to the donor/acceptor interface, whose signature was observed by UV–vis absorption. Promising photovoltaic performances could be achieved in a standard device configuration. The corresponding power conversion efficiency of 4.5% is above the value achieved previously with a comparable polymer using benzo [2,1,3]thiadiazole instead of Py as acceptor unit