Self-polymerization of nano-fibres and nano-membranes induced by two-photon absorption

Malinauskas, Mangirdas; Bickauskaite, Gabija; Rutkauskas, Marius; Paipulas, Domas; Purlys, Vytautas; Gadonas, R.

doi:10.3952/lithjphys.50115

Cited by 35 publications

(24 citation statements)

References 8 publications

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“…[8][9][10] Pure optical light delivery at tight focusing cannot explain the fi nal size of the structure, due to the threshold effect of laser modifi cation via polymerization/ crosslinking, thermal effects within the 3D focal volume, and wet chemistry development, which all affect the fi nal shape and size of the 3D structure. [11][12][13][14][15] Heat accumulation at the focus, defi ned by pulse repetition rate and scan speed, is used to increase the productivity of 3D polymerization and makes thermal issues very important and actively debated. [16][17][18] Polarization effects in laser fabrication in 2D and 3D geometries are now explored in polymerization by DLW.…”

Section: Doi: 101002/adom201600155mentioning

confidence: 99%

Nanoscale Precision of 3D Polymerization via Polarization Control

Rekštytė

Jonavičius

Gailevičius

et al. 2016

Advanced Optical Materials

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COMMUNICATIONand as self-organized nanopatterns induced on a surface, [ 30 ] are among other polarization-related phenomena demonstrated recently.The infl uence of beam polarization orientation on laser processing has been thoroughly studied in the cases of conductive and dielectric solid targets. [ 31,32 ] There are known effects of polarization on the scalar parameters of laser-matter interaction, such as absorption coeffi cient and ionization rate. [33][34][35][36] It is also known that heat conduction fl ux (vector) in plasma might be dependent on the direction of the imposed fi eld. [ 37 ] In what follows, these effects are considered in succession: (i) accumulation from multiple pulses, (ii) effects of polarization under high-numerical aperture (NA) focusing, and (iii) the infl uence of the external high-frequency electric fi eld on electronic heat conduction. The latter contribution has not yet been considered in laser fabrication under tight focusing. All these photomodifi cation mechanisms occur simultaneously and affect polymerization, which takes approximately a millisecond for common photoresists [ 38 ] at a >90% voxel overlap at typical writing velocity of 100 µm s -1 for widespread laser 3D nanolithography. [ 39 ] In this paper, a systematic analysis via modeling and experiments is presented in order to reveal polarization effects, their infl uence on the feature size (resolution), and the coupling between thermal gradient and polarization in DLW.To study and demonstrate the polarization effects, 3D suspended resolution bridges at various angles, α , between the linear polarization and scanning direction were fabricated on a glass substrate ( Figure 1 inset in (a); see details in the Experimental Section). The line-width difference was 10%-20% (varying exposure) under typical polymerization conditions for the linearly polarized pulses. The largest width of a 3D bridge was observed when the scan direction was perpendicular to the orientation of linear polarization, α = π / 2 ( E ⊥ v s ). The heightto-width ratio of the suspended lines was dependent on the orientation of linear polarization and changed between 3.07 and 3.44; self-focusing was not present under our experimental conditions. [ 40 ] Detailed analysis of polarization, threshold, and heat accumulation effects, which are all important, are discussed next.For the experimental conditions used, the focal spot diameter (at 1/ e 2 ) can be calculated as d f = 1.22 λ /NA = 898 nm assuming, for simplicity, a Gaussian intensity profi le. However, at such tight focusing it is necessary to use the vectorial Debye theory (specifi cs [ 41 ] can be found in Section A, Supporting Information), which predicts an ellipsoidal focal spot with two lateral cross sections: W l = 790 nm and W s = 572 nm for long and short cross sections, respectively (or 500 and 360 nm at full width at half maximum (FWHM)) for the actual experimental

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Section: Doi: 101002/adom201600155mentioning

confidence: 99%

Nanoscale Precision of 3D Polymerization via Polarization Control

Rekštytė

Jonavičius

Gailevičius

et al. 2016

Advanced Optical Materials

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“…6(b), exposure time 0.5 s and irradiation dose ~82.5 mW·s). The increased laser irradiation dose initiates the photo-polymerization reactions over the larger area, and when photo-modified regions are close to each other the self-polymerization effect initiated by radicals diffusion [29] starts to act and in such a way the "comb" structure is formed (Fig. 6(c)).…”

Section: Structures Fabricated By Holographic Lithography With a Diffmentioning

confidence: 99%

Fabrication of periodic micro-structures by holographic lithography

Stankevičius¹,

Gedvilas²,

Voisiat³

et al. 2013

Lith. J. Phys.

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The principles of the holographic lithography technique are reviewed, and the ability in the formation of structures with different periods by the holographic lithography technique in SZ2080 is demonstrated. The influence of laser exposure, phase shift between interfering laser beams, and the used laser wavelength on the structures fabricated by the four-beam interference technique has been studied. It is shown that by using the interfering beams with a different phase is it possible to reduce the period of the structure √ − 2 times compared to the four interfering beams of the same phase. Fabrication of micro-structures by the holographic lithography technique can be realized via multi-photon and single-photon polymerization processes. The structures created by these two techniques are compared. Finally, in the experiments with the five-beam interference, the doubleperiod effect was observed by adding the zero-order beam with a low intensity. The fabricated periodic microstructures have the potential to be used as a scaffold for cell growth and micro-optics.

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“…The contact points between old and freshly extruded logs creates cooling points with surface tension pulling a liquid polymer by surface tension gradient towards colder regions [48]. This is a similar effect to a so-called "repolymerization" observed in DLW lithography, were overexposed regions seem to self-form repetitive structures in 1D [49] and 2D [50] manners. Despite that, such log pile micro-sieve structures having undercuts were successfully manufactured without any sacrificial substructures or support materials.…”

Section: D Printing Via Fused Filament Fabricationmentioning

confidence: 56%

3D Microporous Scaffolds Manufactured via Combination of Fused Filament Fabrication and Direct Laser Writing Ablation

et al. 2014

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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 Micromachines 2014, 5 840 porosity (20%-60%) and consisted of desired volume pores (∼0.056 µm 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.

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Self-polymerization of nano-fibres and nano-membranes induced by two-photon absorption

Cited by 35 publications

References 8 publications

Nanoscale Precision of 3D Polymerization via Polarization Control

Nanoscale Precision of 3D Polymerization via Polarization Control

Fabrication of periodic micro-structures by holographic lithography

3D Microporous Scaffolds Manufactured via Combination of Fused Filament Fabrication and Direct Laser Writing Ablation

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