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4-Dimensional printing for adaptive optoelectronic components

Periodic Reporting for period 4 - xPRINT (4-Dimensional printing for adaptive optoelectronic components)

Reporting period: 2021-03-01 to 2022-02-28

3D printing technologies are currently changing the ways objects and products are manufactured, introducing novel design and fabrication rules for building complex and highly interconnected devices. 3D printing technologies are rapidly evolving from prototyping tools to large-scale manufacturing technologies, also in photonics and optoelectronics. In these fields, main challenges are related to the specific requirements in terms of (a) optical properties of the used materials (e.g. absorption coefficients, refractive index, luminescence, optical gain, nonlinear optical response), either passive or active, (b) spatial resolution needed for achieving smooth surfaces and homogeneous 3D structures, and (c) uniformity of interfaces between diverse materials. Moreover, most of the optical components currently available by 3D printing are passive and static, i.e. they are designed to perform a specific task, and cannot be reconfigured or adapt themselves to the varying conditions of their surrounding environment. The realization of optical and photonic devices with properties tailorable by external stimuli and 3D complex and non-planar architectures would enable novel photonic devices with advanced functionalities and high stability, and open new opportunities for system integration and for the decrease of material waste. xPRINT aims at introducing novel additive manufacturing approaches for printing 4-dimensional optical components, namely optical components and devices which have complex 3D architecture and optical properties that can change in time in response to external stimuli.
The xPRINT main objectives are: (i) the engineering of additive manufacturing technologies for printing optical materials embedding stimuli-responsive compounds and (ii) the realization of printed optical components for all-optical computing and data storage.
A synergistic approach characterizes the xPRINT scientific workplan, encompassing modelling and diagnostics of the 3D printing processes, as well as advanced process engineering and spectroscopic analysis, specifically targeting photo-active and photo-responsive materials.
The work performed during the project has been focused on engineering additive manufacturing processes for transparent and photo-active materials, the spectroscopic characterization of the printed responsive materials and the demonstration of the capability of the printed photo-active materials to be used as building blocks of an all-optical computing and data storage system. Relevant results have been achieved for the two scientific workpackages of xPRINT, which included research activities focused on 1) modeling of the processes related to 3D printing of polymers, 2) development of methods for real-time process diagnostics, 3) 3D printing of transparent materials and optical interconnects, 4) spectroscopic investigation of light-responsive, printable materials and 5) realization of all-optical computing systems. Such activities have led to various high-quality research and technological achievements, which are summarized in the following:
- modelling of the photo-polymerization processes, for effectively describing 3D printing processes. The cross-linked regions have been modeled as clusters and the photo-polymerization reaction as an aggregation process. Moreover, a phenomenological model of photo-polymerization process has been introduced to account for polymerization processes whose kinetics is affected by size effects.
- Development of experimental methods for in-situ and real-time monitoring of 3D printing. An innovative methodology based on the measurement of the UV light back-scattered by cured volumes has been introduced.
-Methodologies for 3D printing of transparent materials by either photopolymerization or material extrusion have been experimentally determined. This has led to printed optical components such as 3D freeform optical elements capable of generating complex light intensity patterns, exploitable as cryptographic components.
-Methodologies for 3D printing of light-responsive systems have been implemented, with optical properties (e.g. the refractive index, the birefringence and the absorption spectra) controllable by light modulation.
-3D printing of light-guiding components and experimental investigation of their waveguiding properties.
-Realization of 3D optical structures with tailored light scattering properties enhanced by self-assembly of the constituent nanomaterials, including cellulose nanocrystals.
-Demonstration of a new set of nanostructures 3D materials, whose thermal and light-scattering properties are precisely photo-programmed. These materials have been exploited for the realization of non-colorimetric time-temperature indicators.
-Realization of light-emitting devices, including complex lasers with advanced polarization properties and intensity variable by external electric fields.
-Printing of materials responsive to optical stimuli. These materials constitute the building block of an all-optical computational and data storage unit.
The results of the project have been disseminated to the scientific community through open access publications. The activities aimed at the dissemination of the results have included also presentations at international conferences on photonics, optics and nanomaterials, participation to the European Researchers’ night, and contributions in Research-to-Business and B-to-B events.
All the results achieved by xPRINT have made a significant contribution for advancing the field of additive manufacturing of optical components, light-responsive systems and nanostructured materials beyond the state of the art, leading to various publications and to invited and keynote talks at international conferences on photonics, optics, nanomaterials, organic materials and additive manufacturing. Of particular significance are the achievements concerning (i) the realization of 3D printed optical components capable of generating complex light intensity pattern by refraction; (ii) the development of an original method for process diagnostics; (iii) the realization of 3D optical systems with coherent emission which feature tailored polarization properties, white emission, intensity controllable by electric fields and transient functions; (iv) the development of innovative nanostructured materials with photo-programmable properties and (v) the realization of the first all-optical computing operator and data storage unit made by organic photo-responsive printed materials. The generated scientific knowledge and technological methodologies led to novel devices which were not available before xPRINT, such as printed light-by-light switching systems, non-colorimetric time-temperature indicators, transient heterostructured organic lasers, cryptographic labels, stackable 3D integrated optics and all-optical computing operators. Such new devices are relevant for applications in optical communications and computation, illumination design, smart labels, anti-counterfeiting systems, optical sensing and analytics, advanced imaging and for the supply chain of perishable products.
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