Over the last ten years, the need for organ donors for transplants became critical due to the increased incidence of organ failure [1]. Today, the development of tissue engineering (TE) appears as the best opportunity to overcome this shortage. TE is an interdisciplinary emerging field that aims to restore and maintain human tissue functions by applying engineering and live science principles [2]. However, one of its greatest challenges is the vascularization of tissue for the transport of oxygen and nutrients to prevent cell death. Here an innovative method is proposed to answer vascularization issues and the difficulty to create blood microcapillaries constructs, with a special interest to renal microcapillaries, which allow blood filtration. A cell-bilayer covering a tubular collagen I matrix with a diameter of about 150μm was developed and treated by ultra-short pulse (USP) laser processing in order to selectively remove the collagen core to create a capillary. The precise laser treatment allows indeed for the creation of voids in the fibre-shaped construct which results in the final formation of the capillary. Firstly, experiments were carried on a 2D model of gelatine hydrogel. The hydrogel-laser interaction was parametrically investigated in order to define a window of laser process parameters allowing the creation of voids within the hydrogel. The best window of laser process parameters was then applied to the 3D cell bilayer microfibres. Confocal microscopy examination demonstrated the presence of a lumen through the collagen I matrix without extended damage to surrounding cells. Live/Dead assays were also carried to assess cell viability.
Glass cutting is a subject of high interest for flat panel display and consumer electronics industries. Among laser-based, water jet-based and diamond tool-based existing solutions, ultra-short pulses (USP) appear as a promising technology since this laser technology has the unique capacity to produce highly localized bulk modification owing to non-linear absorption. The cutting using USP lasers could be performed either by full ablation which is slow and generates a lot of dust, by controlled fracture propagation which is slow as well and may lead to path deviation, by stealth dicing which produces rough sidewalls, or by self-breaking induced by in-volume laser irradiation. The laser treatment is often continuous which is not necessary to perform glass cutting and may lead to over-exposure. In this paper we report on single pass glass and sapphire cutting using an USP laser (20W @200kHz or 8W@2MHz) using dash line laser treatment along the cutting trajectory. In-volume energy deposition was done along the glass thickness owing to a Bessel beam. The results will be discussed in terms of sidewall profile and roughness, path deviation, rim sharpness, energy dose and feed rate. Dash line treatment enables to tune the energy deposition and to produce the cutting effect but with a narrower heat affected zone, a better sidewall quality and a more accurate trajectory control of the cutting path.
We investigated the effect of burstmode with nanosecond (ns) time delay between subpulses on sodalime glass volume machining. We observed in tight focusing configuration that the use of burstmode with ns time delay between subpulses does not increase the absorption efficiency and does not bring a significant effect on the heat affected zone diameter with respect to single pulse mode. On the contrary in loose focusing configuration the use of burst mode allows increasing the aspect ratio of the heat affected zone without extra energy absorption. This effect is highly interesting for filamentation glass cutting applications.
Efficient coupling of nanoemitters to photonic or plasmonic structures requires the control of the orientation of the
emitting dipoles related to the emitter. Nevertheless the knowledge of the dipole orientation remains an experimental
challenge. Many experiments rely on the realization of large sets of samples, in order to be able to get one nanostructure
coupled to a well aligned dipole. In order to avoid these statistical trials, the knowledge of the nature of the emitter
(single or double dipole) and its orientation are both crucial for a deterministic approach. Based on the theoretical
development of the point-dipole emission, we propose in this paper to determine the nature and the polarization of two
types of nanoemitters (spherical nanocrystals and dot-in-rod) by the analysis of their emission polarization [1,2]. The
nanoemitters we considered in this study are colloidal semiconductor (CdSe/CdS) nanocrystals with different sizes and
aspect ratio, allowing us to establish a relationship between the geometry of a nanoemitter and the nature and orientation
of its associated radiating dipole.
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