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An investigation of the shrinking behaviour of a zirconium-based sol-gel composite micro-structured by two-photon polymerization is presented and a simple, straightforward methodology allowing the evaluation of shrinkage is suggested. It is shown that volume reduction is directly related to the average laser power (irradiation dose) used for the microfabrication and becomes a critical issue near the polymerization threshold. It is demonstrated that this shrinkage can be employed beneficially to improve the structural resolution. This is demonstrated by the presence of stopbands in the photonic crystal nanostructures fabricated with controlled volume reduction. Well above the polymerization threshold, the studied material exhibits remarkably low shrinkage. Therefore, no additional effort for the pre-compensation of distortion and for the improvement of structural stability is required.

Investigations into the structuring by two-photon polymerization of a nonshrinking, photosensitive, zirconium sol−gel material are presented. This hybrid material can be photostructured even when it contains up to 30 mol % of zirconium propoxide (ZPO); by varying the material’s inorganic content, it is possible to modify and tune its refractive index. The introduction of ZPO significantly increases the photosensitivity of the resulting photopolymer. The fabricated three-dimensional photonic crystal structures demonstrate high resolution and a clear band-stop in the near-IR region. In contrast to common practice, no additional effort is required to precompensate for shrinkage or to improve the structural stability of the fabricated photonic crystals; this, combined with the possibility of tuning this material’s optical, mechanical, and chemical properties, makes it suitable for a variety of applications by two-photon polymerization manufacturing.

Materials processing by ultrafast lasers offers several attractive possibilities for micro/nano fabrication applications. Several exciting prospects arise in the context of surface and bulk laser induced modifications. These form the basis for diverse applications, including the development and functionalization of laser engineered surfaces, the laser transfer of biomolecules and the functionalization of 3D structures constructed by multiphoton stereolithography. In particular, two examples will be discussed in the following, namely a new approach for the development of superhydrophobic, self cleaning surfaces and the fabrication of functionalized scaffolds, for tissue engineering applications.

Photochromic spiropyran molecules are utilized as additives for the development of polymer surfaces whose wetting characteristics can reversibly respond to irradiation with laser beams of properly chosen photon energy. The hydrophilicity is enhanced upon UV laser irradiation due to the photo-induced isomerization of the non-polar spiropyran molecules to the polar merocyanine. The situation is reversed upon green laser irradiation. Micropatterning of the photochromic-polymer films using soft lithography or photo-polymerization techniques affects their wettability towards a more hydrophobic or more hydrophilic behavior depending on the dimensions of the patterned features and on the hydrophilicity/hydrophobicity of the flat surface. The light-induced wettability variations of the structured surfaces are enhanced by up to a factor of three as compared to those on the flat surfaces. This enhancement is attributed to the photo-induced reversible volume changes to the imprinted gratings, which additionally contribute to the wettability changes due to the light-induced photochromic interconversions. (c) Koninklijke Brill NV, Leiden, 2008

Molecular self-assembly is emerging as a viable "bottom-up" approach for fabricating nanostructures. Self-assembled biomolecular structures are particularly attractive, due to their versatile chemistry, molecular recognition properties, and biocompatibility. Among them, amyloid protein and peptide fibrils are self-assembled nanostructures with unique physical and chemical stability, formed from quite simple building blocks; their ability to work as a template for the fabrication of low resistance, conducting nanowires has already been demonstrated. The precise positioning of peptide-based nanostructures is an essential part of their use in technological applications, and their controlled assembly, positioning, and integration into microsystems is a problem of considerable current interest. To date, their positioning has been limited to their placement on flat surfaces or to the fabrication of peptide arrays. Here, we propose a new method for the precise, three-dimensional patterning of amyloid fibrils. The technique, which combines femtosecond laser technology and biotin-avidin mediated assembly on a polymeric matrix, can be applied in a wide variety of fields, from molecular electronics to tissue engineering.

We report the development of a new microstereophotolithography technique for creation of three-dimensional microcomponents by use of a planar, layer-by-layer process of exposure, in which a spatial light modulator is used as a dynamic lithographic mask. The system operates in the UV to take advantage of the wide supply of commercially available photopolymers designed for conventional stereolithography. With this novel procedure it is possible to build components with feature sizes as small as a few micrometers. The experimental setup is briefly described, and the first microcomponent fabricated by this system is shown.

We demonstrate two- and three-dimensional patterning of biological molecules. For the two-dimensional patterning we employ Laser-Induced Forward Transfer of materials in solution. For the three-dimensional patterning we employ femtosecond-laser induced three-photon polymerization, a technique which enables the construction of arbitrary 2D and 3D structures of submicron resolution. Biotin is subsequently attached to the 3D structures via UV-activated crosslinking. The integrity of the photolytically immobilized biotin is confirmed by detecting the binding of fluorescently labeled avidin via fluorescence microscopy.

The modeling, fabrication, cell loading, and mechanical and in vitro biological testing of biomimetic, interlockable, laser-made, concentric 3D scaffolds are presented. The scaffolds are made by multiphoton polymerization of an organic-inorganic zirconium silicate. Their mechanical properties are theoretically modeled using finite elements analysis and experimentally measured using a Microsquisher(®). They are subsequently loaded with preosteoblastic cells, which remain live after 24 and 72 h. The interlockable scaffolds have maintained their ability to fuse with tissue spheroids. This work represents a novel technological platform, enabling the rapid, laser-based, in situ 3D tissue biofabrication.

The wetting characteristics of surfaces of polymers doped with photochromic spiropyran molecules can be tuned when irradiated with laser beams of properly chosen photon energy. In particular, UV laser pulses at 308 nm are responsible for the enhancement of the hydrophilicity of the surfaces, since the embedded non-polar spiropyran molecules convert to their polar merocyanine isomers upon UV absorption. The process is reversed upon irradiation with green laser pulses at 532 nm. When the photochromic-polymeric surfaces are micropatterned using soft lithography or photo-polymerisation techniques, they can change their wettability towards a more hydrophobic or more hydrophilic behaviour depending on the dimensions of the patterned features and on the hydrophilicity-hydrophobicity of the flat surface. Furthermore, the light-induced wettability variations on these structured surfaces are greatly enhanced compared to the flat surfaces. This significant increase to the wettability changes is attributed to the combination of the photochromic interconversions upon laser irradiation together with the photoinduced reversible volume changes of the patterned features.

We report the fabrication of three-dimensional structures of submicrometer resolution by three-photon polymerization. This resolution has been achieved by polymerizing ORMOCER, a UV photocurable organic–inorganic hybrid material, with an ultrafast laser irradiation at 1028?nm. To our knowledge, this is the first demonstration of three-photon polymerization, a process that may allow the fabrication of components of very high resolution.

In this paper, we present research carried out in our laboratory in the field of applications of high power lasers in cleaning surfaces. More specifically, overviews of three different applications are presented; the use of lasers in the cleaning of marble antiquities, in the restoration and cleaning of painted artworks nad in the repair of the paint of ship hulls.

We report the synthesis and evaluation of new highly polar molecules whose combined non- linear and linear optical properties are of interest for frequency doubling. The generic scheme for the syntheses rests on enamine substitutions of tetracyano-p-quinodimethane (TCNQ). In the case detailed, a novel reaction product is reported from the unexpected reaction of triethylamine and TCNQ. In polar solvents such as DMF, the molecule has a charge separated ground state and a measured bipole moment of 45 D. Also in polar solvents, the value for the resonant (beta) coefficient is measured to be -190 X 10-30 esu. Coupled with acceptable transparency at 460 nm ((epsilon) equals 86 M-1 cm-1) this molecule points to a new approach in the design of such materials.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We report the 3D structuring and metallization of a zirconium-based organic-inorganic photosensitive material doped with metal-binding tertiary amine moieties. The influence of the amine group content on the material structurability, the structure resolution and the metallization efficiency was examined. The silver plating technique was also optimized by investigating the metal seeding and reduction parameters. We have compared the silver plating vs. the metal bath techniques and we have found that while the metal bath technique gives good quality metal coatings, ohmic conductivity can only be obtained by silver plating.

The femtosecond laser-induced multi-photon polymerization of a zirconium–silicon based sol–gel photopolymer was employed for the fabrication of a series of micro-optical elements with single and combined optical functions: convex and Fresnel lenses, gratings, solid immersion lenses on a glass slide and on the tip of an optical fiber. The microlenses were produced as polymer caps of varying radii from 10 to 90 µm. The matching of refractive indices between the polymer and substrate was exploited for the creation of composite glass-resist structures which functioned as single lenses. Using this principle, solid immersion lenses were fabricated and their performance demonstrated. The magnification of the composite solid immersion lenses corresponded to the calculated values. The surface roughness of the lenses was below ~ 30 nm, acceptable for optical applications in the visible range. In addition, the integration of micro-optical elements onto the tip of an optical fiber was demonstrated. To increase the efficiency of the 3D laser polymerization, the lenses were formed by scanning only the outer shell and polymerizing the interior by exposure to UV light.

Multiphoton polymerization has been developed as a direct laser writing technique for the preparation of complex 3D structures with resolution beyond the diffraction limit of light. The combination of two or more hybrid materials with different functionalities in the same system has allowed the preparation of structures with advanced properties and functions. Furthermore, the surface functionalization of the 3D structures opens new avenues for their applications in a variety of nanobiotechnological fields. This paper describes the principles of 2PP and the experimental set-up used for 3D structure fabrication. It also gives an overview of the materials that have been employed in 2PP so far and depicts the perspectives of this technique in the development of new active components.

Two-photon polymerisation of photosensitive materials has emerged as a very promising technique for the fabrication of photonic crystals and devices. In this paper we present our investigations into the structuring by two-photon polymerisation of a new class of photosensitive sol-gel composites exhibiting ultra-low shrinkage. We particularly focus on two composites, the first containing a zirconium alkoxide and the second a nonlinear optical molecule. The three-dimensional photonic crystal structures fabricated using these materials demonstrate high resolution and clear band- stops in the near IR region.

Bio-microarray fabrication has been the focus of much research in recent years, as they are envisaged to play an important part in genomic studies, protein identification, drug discovery and screening. We demonstrate both 2D and 3D biomolecules patterning using techniques which enable the construction of arbitrary two and three-dimensional shapes, not restricted to array-based shapes. For the 2D printing, Laser-Induced Forward Transfer (LIFT) is employed to deposit controlled and viable micropatterns of the Horseradish Peroxidase (HRP) and the functionality of the transferred materials is shown. For the 3D printing, firstly microstructures are made employing multiphoton polymerisation and then biotin is subsequently immobilised on the surface of the structures by excimer laser photo-activation of photobiotin and further exposed to fluorescently labelled streptavidin. The specificity of the binding is demonstrated.

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.

We demonstrate the enhancement of the wetting properties of smart photochromic surfaces by a specifically developed, gentle interferometric patterning employing green light. We realized photochromic gratings with 2.5-10.0 mu m period by a blend consisting of a green-curable matrix and spiropyran molecules. The structured surfaces exhibit photocontrolled and reversible wettability, and enhanced hydrophilicity with respect to the native substrates. The dynamics of liquid spreading onto the gratings was also investigated, and the wetting behavior analyzed according to Wenzel's [Ind. Eng. Chem. 28, 988 (1936)] model for rough surfaces. These results indicate switchable gratings as promising functional components for microfluidics and modulation, and green-light interferometry as a reliable lithographic method for patterning organics without degradation or photochemical reactions. (c) 2006 American Institute of Physics.

A new stereophotolithography technique utilizing a spatial light modulator ~SLM! to create threedimensional components with a planar, layer-by-layer process of exposure is described. With this procedure it is possible to build components with dimensions in the range of 50 mm–50 mm and feature sizes as small as 5 mm with a resolution of 1 mm. A polysilicon thin-film twisted nematic SVGA SLM is used as the dynamic photolithographic mask. The system consists of eight elements: a UV laser light source, an optical shutter, beam-conditioning optics, a SLM, a multielement reduction lens system, a high-resolution translation stage, a control system, and a computer-aided-design system. Each of these system components is briefly described. In addition, the optical characteristics of commercially available UV curable resins are investigated with nondegenerate four-wave mixing. Holographic gratings were written at a wavelength of 351.1 nm and read at 632.8 nm to compare the reactivity, curing speed, shrinkage, and resolution of the resins. These experiments were carried out to prove the suitability of these photopolymerization systems for microstereolithography.

The optical characteristics of two commercially available UV curable epoxy resins are investigated using nondegenerate four-wave mixing. The materials assessed are optimized for use with a UV argonion laser. The holographic gratings were written at a wavelength of ? 5351.1 nm for an irradiance range 0.5 to 3.0 W/cm2 and read at ? 5632.8 nm to compare the reactivity, curing speed, shrinkage, and resolution of the resins. These experiments were carried out to prove the suitability of the photopolymerization systems for microstereolithography.

We present investigations into the fabrication of photonic structures by direct laser-writing and nanoimprint lithography using organic-inorganic hybrid materials that have (i) nonlinear optical properties and (ii) can be selectively covered with metal. Direct laser-writing by two-photon polymerization (2PP) allows the fabrication of three-dimensional (3D) structures with a resolution beyond the diffraction limit [1]. The polymerization process is initiated when the beam of an ultra-fast infrared laser is tightly focused into the volume of a transparent, photosensitive material. The technique has been employed successfully in the fabrication of nano-photonic structures and devices.

Bio-micro-array fabrication and biological molecules patterning has been the focus of much research in recent years, as they are envisaged to play an important part in genomic studies, drug discovery and screening, protein identification and scaffolding development for tissue engineering. A number of different approaches have been examined for fabricating patterned biological surfaces. Almost in all cases, patterning of biomolecules has been two-dimensional. We demonstrate both 2D and 3D biotin patterning using techniques which enable the construction of arbitrary two and three dimensional shapes, not restricted to array-based shapes. For the 2D printing, Laser Induced Forward Transfer (LIFT) is employed to deposit controlled and viable micro-patterns of biotin. The activity and the functionality of the transferred materials are shown. For the 3D printing, firstly micro-structures are made employing multi-photon polymerisation. Biotin is subsequently immobilised on the structures surface by excimer laser photo-activation of photobiotin and further incubated with fluorescent labelled streptavidin. The specificity of the binding is demonstrated. The methods allow not only prototyping but also direct device construction.

Two-photon polymerization is a nonlinear optical technique, which allows the fabrication of complex 3D structures with submicron resolution. In this contribution our results on application of novel hybrid materials for 3D microstructing is reported.

We report on the fabrication of a Fabry-Perot optical resonator on the endface of a SMF28 fibre, by employing Direct Laser Writing by multi-photon polymerization. We explore this fibre sensing probe for measuring the vapour of common organic solvents. The device developed has been optimised for operation at the spectral region lying between 1445nm and 1655nm, while being interrogated in reflection mode using a simple 50/50 fibre coupler.

The ability to synthesise bioresponsive systems and selectively active biochemistries using polymer-based materials with supramolecular features has led to a surge in research interest directed towards their development as next generation biomaterials for drug delivery, medical device design and tissue engineering.

Summary form only given. Bone is the second most common transplantation tissue after blood. While the use of bone grafts remains the optimum choice, the problems associated with them has made the use of synthetic implants ever more popular. Over the last decade, there has been a lot research into the development of engineered new bone, to replace damaged tissue. An important part of this research effort has gone into the development of three-dimensional porous scaffolds, to support and guide the new cells.Here, we describe our research into the fabrication and evaluation as bone scaffolds of 3D biodegradable structures made using Direct fs Laser Writing (DLW). The material we use is a photostructurable polylactide-based material (PLA) synthesized for this purpose. We test its degradation in vitro in PBS and we show that the material looses one third of its weight after six weeks, therefore allowing the slow release of an implanted scaffold. We demonstrate the fabrication of artificial scaffolds with precisely controlled geometries and different pore sizes and we test them for up to eight weeks using the mouse pre-osteoblastic cell line MC3T3-E1. Our results show good cell adhesion and a preference to scaffolds with 86% porosity, compare to other porosities studied. Our study shows that DLW is a suitable technique for the fabrication of 3D biodegradable scaffolds for bone repair and other tissue engineering applications.

Single ultra-short pulses with a vortex phase profile have been used to fabricate periodically modulated hollow cylinders via multi-photon polymerization. Fabrication and spectral characterization of these objects are presented.

A split-cube-resonator-based metamaterial structure that can act as a polarization- and direction-selective perfect absorber for the infrared region is theoretically and experimentally demonstrated. The structure, fabricated by direct laser writing and electroless silver plating, is comprised of four layers of conductively-coupled split-cube magnetic resonators, appropriately rotated to each other to bestow the desired electromagnetic properties. We show narrowband polarization-selective perfect absorption when the structure is illuminated from one side; the situation is reversed when illuminating from the other side, with the orthogonal linear polarization being absorbed. The absorption peak can be tuned in a wide frequency range by a sparser or denser arrangement of the split cube resonators, allowing to cover the entire atmospheric transparency window. The proposed metamaterial structure can find applications in polarization-selective thermal emission at the IR atmospheric transparency window for radiative cooling, in cost-effective infrared sensing devices, and in narrowband filters and linear polarizers in reflection mode.

We report on the fabrication of high resolution 3D scaffolds of polylactide-based materials using direct laser writing and we explore their use as neural tissue engineering scaffolds.

Tunable-ring Airy beams are experimentally generated and employed for the fabrication of large three-dimensional structures with high resolution using multi-photon polymerization. We demonstrate that these beams can be adjusted to abruptly autofocus over an extended range of working distances while keeping their voxel shape and dimensions almost invariant. This striking property together with the real-time electronically controlled focus tuning makes these beams ideal candidates for long-range multi-photon polymerization. Moreover, the well-controlled remote localized deposition of energy can also impact many other fields of linear and nonlinear optics, like filamentation and remote high-power terahertz generation.