Propulsion of bubble-based acoustic microswimmers

Acoustic microswimmers present a great potential for microfluidic applications and targeted drug delivery. Here, we introduce armored microbubbles (size range, 10–20 μm) made by three-dimensional microfabrication, which allows the bubbles to last for hours even under forced oscillations. The acoustic resonance of the armored microbubbles is found to be dictated by capillary forces and not by gas volume, and its measurements agree with a theoretical calculation. We further measure experimentally and predict theoretically the net propulsive flow generated by the bubble vibration. This flow, due to steady streaming in the fluid, can reach 100 mm/s, and is affected by the presence of nearby walls. Finally, microswimmers in motion are shown, either as spinning devices or free swimmers.P. M. acknowledges financial support from the European Community’s Seventh Framework Programme (FP7/2007-2013) ERC Grant Agreement Bubbleboost No. 614655. This work has been performed with the help of the “Plateforme Technologique Amont” de Grenoble, with the financial support of the “Nanosciences aux limites de la Nanoélectronique” Foundation. Support from the EPSRC (T. A. S.) and from a Marie Curie Grant (E. L.) is also gratefully acknowledged.This is the author accepted manuscript. The final version is available from American Physical Society via http://dx.doi.org/10.1103/PhysRevApplied.4.06401

"Optically driven Archimedes micro-screws for micropump application"

International audienceArchimedes micro-screws have been fabricated by three-dimensional two-photon polymerization using a Nd:YAG Q-switched microchip laser at 532nm. Due to their small sizes they can be easily manipulated, and made to rotate using low power optical tweezers. Rotation rates up to 40 Hz are obtained with a laser power of 200 mW, i.e. 0.2 Hz/mW. A photo-driven micropump action in a microfluidic channel is demonstrated with a non-optimized flow rate of 6pL/min. The optofluidic properties of such type of Archimedes micro-screws are quantitatively described by the conservation of momentum that occurs when the laser photons are reflected on the helical micro-screw surface

New initiator for two-photon absorption induced polymerization with a microlaser at 1.06 μm

International audienceTwo-photon absorption (TPA) induced polymerization is a very promising way for three-dimensional (3D) microfabrication. However, the necessity to use onerous femtosecond Ti:sapphire lasers appears as a major drawback for this technology. We present a new symmetrical conjugated ketone with terminal amino groups that can initiate TPA photopolymerization of acrylates when irradiated with an inexpensive Nd-YAG microlaser. This compound shows broad band TPA between 800 nm and 1100 nm with a cross-section of 100×10−50 cm4 s photon−1 at the photoinitiation wavelength (1.06 μm). The efficiency of this new initiator is evaluated by the determination of the threshold of absorbed energy density for polymerization

Efficient initiators for two-photon induced polymerization in the visible range

International audienceWe present two derivatives of biphenyl or fluorene symmetrically substituted, which could initiate the two-photon absorption (TPA) photopolymerization of acrylates in the visible range. Both compounds show broadband TPA between 500 and 650 nm with cross-sections of, respectively, 30 and 80×10−50 cm4 s photon−1 at 532 nm, the photoinitiation wavelength. Threshold energies and dynamic ranges for polymerization were measured in both cases. As expected, the fluorene derivative was slightly more efficient than the biphenyl one. Our initiators appeared to be orders of magnitude more sensitive than the commercial UV ones, commonly used for TPA photopolymerization

Le droit international selon Hans Kelsen

À l’heure où la Cour pénale internationale se voit critiquée par nombre de ses détracteurs, cet ouvrage propose une analyse de la judiciarisation internationale au prisme de l’un de ses initiateurs : Hans Kelsen. Le théoricien du normativisme a réfléchi sur le droit international, notamment lors de son exil aux États-Unis. Il ne cessera de promouvoir une Organisation des Nations unies dont le pivot serait une juridiction. Tout en permettant de mieux saisir la trajectoire intellectuelle du juriste viennois outre-Atlantique, les études rassemblées ici soulignent les tensions inhérentes à l’établissement des premiers tribunaux militaires après la Seconde Guerre mondiale, qu’elles concernent la reconnaissance d’un individu justiciable ou bien l’application du principe de non-rétroactivité. Fondé notamment sur la présentation et la traduction de textes consacrés à la responsabilité et à la poursuite des criminels de guerre, cet ouvrage rentre en résonance avec les dilemmes contemporains qui entourent l’établissement d’une justice pénale internationale.In a context of International Criminal Court crisis, this book analyzes the international legalization process based on one of its intiators : Hans Kelsen. The theorist of normativism did not exclude International Law, especially during his exile in the United States. He promoted an United nations Organization whose pivot was a jurisdiction. Providing a new understanding of the intelectual trajectory of the Viennese legal expert, these studies underline the tensions behind the creation of the first military courts after the Second World War, concerning the recognition of the individual as a litigant or the application of the non-retroactivity principle. Thanks to the introduction and the translation of texts dedicated to the responsbility and the prosecution of war criminals, this book resonates with the current relating to the institutlionalization of international criminal justice