Nanoscale precision of 3D polymerisation via polarisation control

A systematic analysis of polarization effects in a direct write femtosecond laser 3D lithography is presented. It is newly shown that coupling between linear polarization of the writing light electric field and temperature gradient can be used to fine-tune feature sizes in structuring of photoresists at a nanoscale. The vectorial Debye focusing is used to simulate polarization effects and a controlled variation up to 20% in the linewidth is shown experimentally for the identical axial extent of the polymerised features. The revealed mechanisms are relevant for a wide range of phenomena of light-matter interaction at tight focusing in laser-tweezers and in plasmonic or dielectric sub-wavelength focusing where strong light intensity and thermal gradients coexist.Comment: 15 pages, 3 figure

Reversible deformation in hybrid organic-inorganic photoresists processed by ultrafast direct laser write technique

We report on reversible deformation in photoresist structures patterned using femtosecond direct laser write technique. Significant swelling and shrinkage of exposed features by up to 10% in negative-tone hybrid organicinorganic Zr containing photoresist SZ2080 were found to occur during wet development and rinse following the laser processing. Amount of swelling and shrinkage is controllable within 10% margin via use of different rinse agents and the shrinkage-swelling cycle can be repeated many times. Simple interpretation of this phenomenon is presented, and several potential application areas in diffractive optics, micro mechanics, actuation, and environmental sensing are outlined

Femtosecond pulsed light polarization induced effects in direct laser writing 3D nanolithography

We demonstrate how the coupling between (i) polarization of the writing laser beam, (ii) tight focusing and (iii) heat conduction affects the size, shape and absorption in the laser-affected area and therefore the polymerization process. It is possible to control the sizes of 3D laser-produced structure at the scale of several nanometers. Specifically we were able to tune the aspect ratio of 3D suspended line up to 20% in hybrid SZ2080 resist. The focal spot of tightly focused linearly polarized beam has an elliptical form with the long axis in the field direction. It is shown here that this effect is enhanced by increase in the electronic heat conduction when polarization coincide with temperature gradient along with the absorption. Overlapping of three effects (i- iii) results in the difference of several tens of nanometers between two axes of the focal ellipse. Narrow line appears when polarization and scan direction coincide, while the wide line is produced when these directions are perpendicular to each other. The effect scales with the laser intensity giving a possibility to control the width of the structure on nanometer scale as demonstrated experimentally in this work. These effects are of general nature and can be observed in any laser-matter interaction experiments where plasma produced by using tight focusing of linear-polarized light

Nano-groove and 3D fabrication by controlled avalanche using femtosecond laser pulses

We report fabrication of sub-100 nm resolution structures by ablation on the surface of sapphire using femtosecond laser pulses. A single 50-70 nm wide groove was recorded by laser ablation via a controlled ripple formation on the surface. Ripples are created by breakdown due to a sphere-to-plane formation of an ionisation below surface in a similar way as the bulk ripples. Different thresholds for the ripples formed parallel and perpendicular to direction of the laser scan were observed. In a sol-gel photo-polymer SZ2080 and thermo-polymer polydimethylsiloxane, free-standing 3D structures were formed without use of two-photon absorbing photo-sensitizers. Both cases of the surface and bulk structuring were achieved via a controlled avalanche, which dominated ionisation of materials

Combination of additive and subtractive laser 3D microprocessing in hybrid glass/polymer microsystems for chemical sensing applications

We present a novel hybrid glass-polymer micromechanical sensor by combining two femtosecond laser direct writing processes: laser illumination followed by chemical etching of glass and two-photon polymerization. This incorporation of techniques demonstrates the capability of combining mechanical deformable devices made of silica with an integrated polymer structure for passive chemical sensing application. We demonstrate that such a sensor could be utilized for investigating the elastic properties of polymeric microstructures fabricated via the two-photon polymerization technique. Moreover, we show that polymeric microstructure stiffness increases when immersed in organic liquids. (C) 2017 Optical Society of Americ

The influence of certain LAB sourdough fermentation of the Jerusalem artichoke (Helianthus tuberosus L.) tubers on the quality and safety of wheat bread

The main focus in this study was to investigate the effects on wheat bread safety and quality due to addition of Jerusalem artichoke (Helianthus tuberosus L.) tubers, fermented by different lactic acid bacteria (LAB) strains that produce bacteriocin-like inhibitory substance (BLIS). For the Jerusalem artichoke (JA) sourdough fermentation several different LAB (Pediococcus acidilactici KTU05-7, Pediococcus pentosaceus KTU05-8, Pediococcus pentosaceus KTU05-9, Lactobacillus sakei KTU05-6, Pediococcus pentosaceus KTU05-10) were used. The mass fraction of fermented or untreated tubers of JA in the wheat bread formula was 15%. We found experimentally that JA tubers fermented with LAB contained more L(+) lactic acid than D(-) lactic acid, which resulted in safer products than by spontaneous treatment. The concentrations of biogenic amines in all analysed fermented JA products were far below levels causing a health risk, while the products fermented with LAB contained lower amounts by 50; 55; 55; 68 and 54 %, respectively. We also found that the proteolytic activity of LAB does not correlate with acrylamide content in bread made with JA additives (R = 0.3683; P = 0.2015), but there was a strong correlation between acrylamide and the sourdough pH (R = 0.8801; P = 0.0056), and with LAB amylase activity excreted in JA material (R = 0.9719; P = 0.003). We conclude that the use of lactic acid fermentation allows wheat bread enrichment with 15 % JA fermented with LAB, without deterioration in bread quality parametersBiochemijos katedraBotanikos sodasKauno technologijos universitetasLietuvos sveikatos mokslų universitetas. Veterinarijos akademijaVytauto Didžiojo universiteta

3D microporous scaffolds manufactured via combination of fused filament fabrication and direct laser writing ablation

A 3D printing fused filament fabrication (FFF) approach has been implemented for the creation of microstructures having an internal 3D microstructure geometry. These objects were produced without any sacrificial structures or additional support materials, just by precisely tuning the nozzle heating, fan cooling and translation velocity parameters. The manufactured microporous structures out of polylactic acid (PLA) had fully controllable porosity (20%-60%) and consisted of desired volume pores (similar to 0.056 mu m(3)). The prepared scaffolds showed biocompatibility and were suitable for the primary stem cell growth. In addition, direct laser writing (DLW) ablation was employed to modify the surfaces of the PLA structures, drill holes, as well as shape the outer geometries of the created objects. The proposed combination of FFF printing with DLW offers successful fabrication of 3D microporous structures with functionalization capabilities, such as the modification of surfaces, the generation of grooves and microholes and cutting out precisely shaped structures (micro-arrows, micro-gears). The produced structures could serve as biomedical templates for cell culturing, as well as biodegradable implants for tissue engineering. The additional micro-architecture is important in connection with the cell types used for the intention of cell growing. Moreover, we show that surface roughness can be modified at the nanoscale by immersion into an acetone bath, thus increasing the hydrophilicity. The approach is not limited to biomedical applications, it could be employed for the manufacturing of bioresorbable 3D microfluidic and micromechanic structures