A series of nonlinear optical chromophores based on configurationally locked polyene are synthesized, and the single crystal growth from the melt are investigated. The chromophores consist of a π-conjugated hexatriene bridge between the dialkylamino or methoxy electron donors and the dicyanomethylidene electron acceptor. The physical and nonlinear optical properties and the single crystal X-ray structures of these chromophores are characterized. Specifically, the chromophore 2-{3-[2-(4-dimethylaminophenyl)vinyl]-5,5-dimethylcyclohex-2-enylidene}malononitrile (DAT2) exhibits a strong powder second-harmonic generation signal of about 2 orders of magnitude greater than that of urea and a large temperature difference of 80 °C between the melting temperature and the recrystallization temperature. Finally, we demonstrate the growth of single crystalline thin films of DAT2 by a Bridgman-type melt growth technique, which gives a new direction for organic nonlinear optical crystal engineering using melt-growth techniques.

A series of new nonlinear optical chromophores based on configurationally locked polyenes (CLPs) with chiral pyrrolidine donors are synthesized. All CLP derivatives exhibit high thermal stability with decomposition temperatures Td at least >  270 °C. Acentric single crystals of enantiopure D‐ and L‐prolinol‐based chromophores with a monoclinic space group P21 exhibit a macroscopic second‐order nonlinearity that is twice as large than that of analogous dimethylamino‐based crystal. This is attributed to a strong hydrogen‐bonded polar polymer‐like chain built by these molecules, which is aligned along the polar crystallographic b‐axis. Five α‐phase CLP crystals with different donors grown from solution exhibit a reversible or irreversible thermally induced structural phase transition to a β‐phase. These phase transitions are unusual, changing the crystal symmetry from higher to lower at increasing temperatures, for example, from centrosymmetric to non‐centrosymmetric, enhancing their macroscopic second‐order nonlinear optical properties.

Additive manufacturing methods 1-4 using static and mobile robots are being developed for both on-site construction 5-8 and off-site prefabrication 9, 10 . Here we introduce a new method of additive manufacturing, referred to as Aerial Additive Manufacturing (Aerial-AM), that utilizes a team of aerial robots inspired by natural builders 11 such as wasps who use collective building methods 12, 13 . We present a scalable multi-robot 3D printing and path planning framework that enables robot tasks and population size to be adapted to variations in print geometry throughout a building mission. The multi-robot manufacturing framework allows for autonomous 3D printing under human supervision, real-time assessment of printed geometry and robot behavioural adaptation. To validate autonomous Aerial-AM based on the framework, we develop BuilDrones for depositing materials during flight and ScanDrones for measuring print quality, and integrate a generic real-time model-predictive-control scheme with the Aerial-AM robots. In addition, we integrate a dynamically self-aligning delta manipulator with the BuilDrone to further improve manufacturing accuracy to 5mm for printing geometry with precise trajectory requirements, and develop four cementitious-polymeric composite mixtures suitable for continuous material deposition. We demonstrate proof-of-concept prints including a cylinder of 2.05m with a rapid curing insulation foam material and a cylinder of 0.18m with structural pseudoplastic cementitious material, a light-trail virtual print of a dome-like geometry, and multi-robot simulations.

We report on the production of organic single crystalline thin films for integrated nonlinear optical applications by a vapor growth technique. The configurationally locked polyene chromophore 2-{3-[2-(4-dimethylaminophenyl)vinyl]-5,5-dimethylcyclohex-2-enylidene} malononitrile (DAT2) that was used exhibits a noncentrosymmetric crystalline arrangement with monoclinic point group symmetry 2. It shows a second harmonic generation signal of about 2 orders of magnitude greater than that of urea. The grown DAT2 films are single crystalline and exhibit good optical quality and suitable size (area of ∼5 × 3 mm2 and the thickness in the range of 0.2−5 μm) for fabrication of photonic devices. Growth rates of a few hours have been achieved. Furthermore, the edges of the films are sharp and flat, which greatly reduces the additional processing requirements for applications.

Configurationally locked polyene crystals grown in the absence and in the presence of their tailor-made auxiliaries, which are slightly modified substrate molecules, were investigated. The effects of the tailor-made auxiliaries on the crystal characteristics were investigated by X-ray crystal structure analysis and nonlinear optical and photoluminescent measurements. The substrate crystals of 2-{3-[2-(4-dimethylaminophenyl)vinyl]-5,5-dimethylcyclohex-2-enylidene}malononitrile (DAT2) and 2-{3-[2-(4-pyrrolidinphenyl)-vinyl]-5,5-dimethylcyclohex-2-enylidene}malononitrile (PyT1) exhibit a strong powder second harmonic generation signal of about 140 and 80 times that of urea at a fundamental wavelength of 1.9 µm. Although the investigated substrate polyene molecules DAT2 and PyT1 show very similar crystal structures in the absence of auxiliaries, in the presence of the tailor-made additives with the same modification of the corresponding substrate molecules, the DAT2 crystal exhibits a morphological change and the PyT1 crystal exhibits a polymorphic change.