Grayscale laser lithography is capable of producing continuous-relief (2.5D) structures down to the micro- and nanoscale for applications such as micro-optics, micro-electromechanical systems and functional surfaces. The present work evaluates build accuracy by employing benchmark artefacts having an active area of up to 1 mm × 1 mm and a structure depth of up to 50 μm with a resolution of 1 μm as models for the production of 2.5D structures with a wide range of representative features in terms of elevation, slope, curvature, aspect ratio and area density. The topography of manufactured samples is determined via laser scanning confocal microscopy and 3D optical microscopy based on white light interferometry, with alignment algorithms developed within MATLAB employed to evaluate local build error over the entire surface. Further to the incident laser energy density within each region, the applied energy in adjacent regions is found to influence build accuracy due to the laser intensity distribution, light scattering and photochemical reaction effects, with the area density and aspect ratio of model features found to be of strong influence on outcomes. The results imply that greater build accuracy can be achieved by basing process parameters on not only the local model height but also that within adjacent regions. The present work was performed within the Horizon Europe project “Automated Maskless Laser Lithography Platform for First Time Right Mixed Scale Patterning” (OPTIMAL, Grant Agreement No. 101057029), with the aim of facilitating automated approaches for error correction and accuracy optimization.
We present the multimodal characterization of thin polymeric membrane by digital holography-based methods. Herein, two microscope techniques had been chosen to reveal the morphology of membranes, which are conventional off-axis Digital Holography (DH) and Space-Time Digital Holography (STDH). The complementary features of the different methods allow for a bottom-up analysis of the related membranes. Meanwhile, the dynamic forming process of polymeric membrane at the air-water interface is revealed in real-time by CDH. By comparing the imaging results of different methods, the application range of different imaging methods is analyzed in detail.
With the improvement in industrial production technologies, many products related to thin-film materials have been produced, especially in the field of daily chemistry. Because of its special physical and chemical properties, film material has become the best carrier, and a detailed measurement of its characteristics is highly required. The thickness characterizing of the thin film is a long-term challenge, one of the well-known methods is the interferometry. Recently, digital holographic approaches have been considered as one of the best candidates for thin film thickness mapping; it allows real-time, contactless, label-free, and full-field thickness measurement. Thanks to above features, holography-based thin film fabrication paradigm has been established rapidly. In this framework, we present a strategy for forming free-standing thin liquid film under the monitoring of Digital Holography (DH): a customized iris diaphragm has been used to stretch the liquid droplet inside to a thin liquid film. Under the condition of quantitatively adjusting the opening speed and radius of the iris, the precise manufacturing of the desired thin film can be achieved. In this case, DH is implemented to provide the thickness distribution of the droplet during stretching; the real-time thickness mapping of thin film builds up a close loop controlling for fabrication process. Based on this strategy, we performed a series experiments of thin liquid films fabrication and the opening process of thin film have been studied by spatiotemporal modeling. The results show that customized iris diaphragm is a good strategy for quantitative fabrication of thin liquid films.
The digital holography method has been implemented to several industrial systems with the aim of improving new products by quantitative measurement. Nowadays, digital holography (DH) has been considered an important measurement tool, owing to the abilities of non-contact, label-free, quantitative, high-resolution and real-time. The inherent characteristics of DH makes it a powerful tool for visualization and testing of soft matter, as well as in-situ and real-time characterization of bottom-up fabrication processes. Herein, we report the most useful applications of soft matter, where the capabilities offered by DH, such as three-dimensional (3D) imaging, extended focus, 3D tracking, full-field analysis, high sensitivity, and wide measurement’s range, permit completely non-invasive characterizations on a full-scale. Taking the advantages of DH measurement, the possibility of numerically managing the complex wavefront scattered or transmitted by the sample under investigation allows the extraction of all information through a full-digital modality. Meanwhile, the numerical diffraction propagation process allows object imaging well-in-focus during dynamic process. This also creates the possibility to retrieve phase-contrast maps that enable quantitative measurements of the sample in full-field mode and 3D. Moreover, DH measurement has good ability to manage and remove aberrations in the optical system using simple and flexible methods, thus simplifying the optical apparatus and measurement operations. Owing to these unique features of DH, we have possibility to better study the world of soft-matter.
Quantitative measurement for thin-film thickness has been a widely studied issue, and, visualizing and characterizing for full-field thin-film evolution can provide effective data support for membrane science, polymer chemistry, biomaterials, applied Chemistry, etc. Interferometry was considered the most useful tool to measure film thickness in past decades. However, there were deficiencies in imaging speed and field of view for conventical interferometric measurement. In this paper, we proposed a fusion method to achieve full-field and quantitative analysis of the thin liquid film at nanoscale by using Digital Holography (DH) and White Light Interferometry (WLI) simultaneously. Compared with our previous holographic studies on thin film measurement, this new method can overcome the shortcomings of the holographic method related to registration and reconstruction. In addition, these parallel experiments can also provide a reference when we have to make a choice between DH and WLI. For the thickness reconstruction process, the entire life cycle registration is no longer required to obtain the thickness information. Moreover, the region where the thin film thickness is less than half the wavelength is now measurable. Thanks to the fusion processing, the film thickness calibration can be obtained without any background subtraction, in the meantime, the background hologram becomes not essential in the holographic recording process.
In this paper, we propose digital holography in transmission configuration as an effective method to measure the time-dependent thickness of polymeric films during bubble blowing. We designed a complete set of experiments to measure bubble thickness, including the evaluation of the refractive index of the polymer solution. We report the measurement of thickness distribution along the film during the bubble formation process until the bubble‘s rupture. Based on those data, the variation range and variation trend of bubble film thickness are clearly measured during the process of expansion to fracture is indicated.
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