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We present a new method for increasing the resolution of direct femtosecond laser writing by multiphoton polymerization, based on quencher diffusion. This method relies on the combination of a mobile quenching molecule with a slow laser scanning speed, allowing the diffusion of the quencher in the scanned area and the depletion of the multiphoton-generated radicals. The material we use is an organic-inorganic hybrid, while the quencher is a photopolymerizable amine-based monomer which is bound on the polymer backbone upon fabrication of the structures. We use this method to fabricate woodpile structures with a 400 nm intralayer period. This is comparable to the results produced by direct laser writing based on stimulated-emission-depletion microscopy, the method considered today as state-of-the-art in 3D structure fabrication. We optically characterize these woodpiles to show that they exhibit well-ordered diffraction patterns and stopgaps down to near-infrared wavelengths. Finally, we model the quencher diffusion, and we show that radical inhibition is responsible for the increased resolution., (© 2012 American Chemical Society)

The aim of this study is to investigate cell adhesion and viability on highly rough polymeric surfaces with gradient roughness ratios and wettabilities prepared by microreplication of laser micro/nano-textured Si surfaces. Negative replicas on polydimethylsiloxane as well as positive ones on a photocurable (organically modified ceramic) and a biodegradable (poly(lactide-co-glycolide)) polymer have been successfully reproduced. The final culture substrates comprised from forests of micron-sized conical spikes exhibiting a range of roughness ratios and wettabilities, was achieved by changing the laser fluence used to fabricate the original template surfaces. Cell culture experiments were performed with the fibroblast NIH/3T3 and PC12 neuronal cell lines in order to investigate how these surfaces are capable of modulating different types of cellular responses including, viability, adhesion and morphology. The results showed a preferential adhesion of both cell types on the microstructured surfaces compared to the unstructured ones. In particular, the fibroblast NIH/3T3 cells show optimal adhesion for small roughness ratios, independent of the surface wettability and polymer type, indicating a non-monotonic dependence of cell adhesion on surface energy. In contrast, the PC12 cells were observed to adhere well to the patterned surfaces independent of the roughness ratio and wettability. These experimental findings are correlated with micromechanical measurements performed on the unstructured and replicated surfaces and discussed on the basis of previous observations describing the relation of cell response to surface energy and rigidity., (© 2011 IOP Publishing Ltd)

The study, preservation and restoration of cultural heritage materials and objects are crucial for obtaining important historical information, maintaining their aesthetic appeal or understanding early technologies. The unique, highly diverse character of cultural heritage items impose the need for rigorous scientific approaches, often incorporating non-invasive, mobile or remote technologies and the valorisation of objects and preservation methodologies. Here, we overview the fundamental aspects in the use of lasers for the analysis and restoration of artworks. For the former purpose, emphasis is placed on the use of Raman and Laser-Induced-Breakdown spectroscopies, both of which have been of increasing importance in the field of Cultural Heritage. The use of lasers for the restoration of artworks, in particular of painted artworks and parchments are described. Studies on model polymeric systems, as well as realistic artefacts, have permitted detailed assessment of the mechanisms and of the effects of the procedure. Finally, we provide an assessment of the potential of new laser-based technologies and techniques for the purpose of conservation/restoration of cultural objects. [ABSTRACT FROM AUTHOR]

The article comments on the use of a laser to clean works of art. Cultural heritage materials can be sensitive, ephemeral and unique. Cleaning and restoration attempts, general storage, use and misuse lead to the build-up of dirt and materials on top of the original work. In order to preserve and avoid causing further damage to the artefacts during cleaning, an awareness of the original material is required during restoration.

The authors demonstrate here a method for three-dimensional patterning of proteins and other biological molecules. The method employs femtosecond-laser-induced three-photon polymerization, a technique which enables the construction of arbitrary two- and three-dimensional structures of submicron resolution. Biotin is subsequently attached to the three-dimensional (3D) structures via UV-activated cross-linking. The integrity of the photolytically immobilized biotin is confirmed by detecting the binding of fluorescently labeled avidin via fluorescence microscopy and via a surface acoustic sensor technique. In all, the technique opens the way for the fabrication of structures with a wide range of biomaterials as well as studying their dynamics within complex 3D structures. [ABSTRACT FROM AUTHOR]

Abstract: Objective: We used laser Doppler spectroscopy to detect hyperactivity of muscle fibers caused by the presence of fibrillations, positive waves and fasciculations. Methods: The proposed method relies upon the dynamic scattering of light by moving particles, which causes a Doppler shift of the original frequency. For resolution of small alterations in frequency the heterodyne detection was used. One hundred seventy-three normal and 109 EMG diagnosed denervated first dorsal interosseous muscles were examined. Results: Denervated muscles with fasciculations showed significant differentiation from control muscles, whereas denervated muscles without fasciculations were not significantly differentiated. The smallest differentiation compared to controls was seen in chronic denervated muscles without spontaneous activity. Conclusions: Presence of fasciculations in denervated muscles allowed Doppler spectroscopy to differentiate them from normal muscles. Presence of atrophy reduced the diagnostic potential of the method. Significance: Our findings can be used as a basis for further improving painless and noninvasive laser Doppler spectroscopy to be used clinically as an alternative to painful and invasive EMG. [Copyright &y& Elsevier]

Abstract: An extensive investigation of the photodegradation of the photochromic molecule 1′,3′-dihydro-1′,3′,3′-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2′-(2H)-indole] in a polymer matrix is studied under irradiation with ultraviolet (UV) laser pulses of 248 and 308nm wavelength. Apart from the effect of the wavelength, the effect of the pulse duration is also presented using pulses of 30ns and 500fs for the 248nm wavelength. To tackle the problem of oxidative degradation upon irradiation of the photochromic molecules which is known to play a principal role in the photodegradation process, we incorporate Iron(II) phthalocyanine molecules in the examined matrices. These molecules upon UV irradiation are dissociated into photoproducts that can interact efficiently with electron acceptor groups in the polymer, partly responsible for the photochromic degradation. The phthalocyanine molecules seem to protect efficiently the photochromic molecules only at low laser fluences. Moreover, in the case of ultrashort pulses the degradation of the photochromic molecules is found to be more intense that in the case of ns pulses, indicating multiphoton absorption mechanisms, unless low laser fluences are used. [Copyright &y& Elsevier]