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Controlling the shape of 3D microstructures by temperature and light
摘要： Stimuli-responsive microstructures are critical to create adaptable systems in soft robotics and biosciences. For such applications, the materials must be compatible with aqueous environments and enable the manufacturing of three-dimensional structures. Poly(N-isopropylacrylamide) (pNIPAM) is a well-established polymer, exhibiting a substantial response to changes in temperature close to its lower critical solution temperature. To create complex actuation patterns, materials that react differently with respect to a stimulus are required. Here, we introduce functional three-dimensional hetero-microstructures based on pNIPAM. By variation of the local exposure dose in three-dimensional laser lithography, we demonstrate that the material parameters can be altered on demand in a single resist formulation. We explore this concept for sophisticated three-dimensional architectures with large-amplitude and complex responses. The experimental results are consistent with numerical calculations, able to predict the actuation response. Furthermore, a spatially controlled response is achieved by inducing a local temperature increase by two-photon absorption of focused light.
关键词： light-induced actuation,pNIPAM,temperature response,stimuli-responsive materials,gray-tone lithography,hetero-microstructures,laser lithography,3D microstructures
更新于2025-09-23 15:22:29
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Liquid Crystal Alignment on the Patterns Produced by Nonlinear Laser Lithography
摘要： Liquid crystal (LC) based devices such as displays, spatial light modulators (SLM) and different switchable phase masks constitute the main part of the graphic information display and light control. Mechanical rubbing and photo-alignment are the most widely used industrial technologies to create anisotropic surfaces for these devices. Recently, nonlinear laser lithography (NLL) was introduced as a fast, cost effective method for large area nano-grating fabrication based on laser-induced periodic surface structuring [1]. Here we report on alignment of nematic LC on NLL treated Ti film deposited on glass for the first time. We demonstrate controllable changes of azimuthal anchoring energy (AAE) depending on processing and additional coating parameters. To create the large area of structured Ti layers we used the experimental scheme of the NLL method, as described in [2]. The setup consists of a home-made femtosecond fiber laser system (up to 1.8 μJ pulse energy at 1 MHz repetition rate), galvanometer-scanner and motorized 3D–translation stage. The samples were 300 nm Ti films deposited on glass. 5x5 mm2 zones were structured by raster scanning of the laser beam over the surface with different parameters. To measure the twist angle and further calculate the AAE we have made combined twist LC cells. LC cells consisted of the tested and reference substrates where the last one was a glass substrate coated with a polyimide PI2555 and processed by the rubbing technique. The first type of the tested substrate was coated with Ti layer and further processed by the NLL method. The second type of the tested substrate was additionally coated with ODAPI. The twist angle was measured by using the combined twist LC cell method. Later, the AAE was calculated from the obtained twist angles of different samples. Fig. 1 (a-c) demonstrates dependencies of the measured twist angles and calculated AAE for different samples. We obtain controllable changes of the anchoring energy in the range between 2x10-6 J/m2 to 10-4 J/m2. The highest AAE 10-4 J/m2 is obtained for the samples which are processed by NLL with post-coating by ODAPI.
关键词： Azimuthal anchoring energy,Liquid crystal alignment,Nonlinear laser lithography,Nematic LC,Ti film
更新于2025-09-23 15:19:57
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Stitch-Free Fabrication of Microoptical Elements Employing Femtosecond Laser 3D Lithography
摘要： Microoptics is a fast expanding field showing huge potential in providing science and industry with small yet highly functional tools for light control at a micro-scale. One of the most promising technologies to produce such elements is 3D laser lithography (3DLL) as it enables fabrication of free-form 3D objects with resolution and surface roughness control down to nm level. Despite current progress there is still some limitations concerning microoptical element printing. In this work we present an approach of synchronizing linear stages and galvo-scanners for rapid (up to several mm/s translation velocity) and stitch-free printing of functional microoptics with the optical grade surface finish and overall size up to several mm. These include mm sized refractive microlenses, Fresnel lenses, microprisms and opaque apertures. All these elements are produced in a single printing step showing the potency of 3DLL as a straight-forward and relatively simple technology to produce microoptics at these sizes. Quality and functionality of these elements are investigated in qualitative and quantitative fashions. Outlook on challenges occurring while working in this size scale is provided, possible solutions to tackle them are proposed.
关键词： 3D laser lithography,linear stages,stitch-free printing,Microoptics,galvo-scanners
更新于2025-09-11 14:15:04