Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging, optical data storage, and lithographic microfabrication. These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order λ3 (where λ is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (δ). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures.

Two-photon polymerization initiators for three-dimensional optical data storage and microfabrication

Additive manufacturing (AM), also known as three-dimensional (3D) printing, has boomed over the last 30 years, and its use has accelerated during the last 5 years AM is a materials-oriented manufacturing technology, and printing resolution versus printing scalability/speed trade-off exists among various types of materials, including polymers, metals, ceramics, glasses, and composite materials Four-dimensional (4D) printing, together with versatile transformation systems, drives researchers to achieve and utilize high dimensional AM Multiple perspectives of the AM of structural materials have been raised and illustrated in this review, including multi-material AM (MMa-AM), multi-modulus AM (MMo-AM), multi-scale AM (MSc-AM), multi-system AM (MSy-AM), multi-dimensional AM (MD-AM), and multi-function AM (MF-AM) The rapid and tremendous development of AM materials and methods offers great potential for structural applications, such as in the aerospace field, the biomedical field, electronic devices, nuclear industry, flexible and wearable devices, soft sensors, actuators, and robotics, jewelry and art decorations, land transportation, underwater devices, and porous structures

Additive manufacturing of structural materials

Additive manufacturing (AM) has gained significant attention due to its ability to drive technological development as a sustainable, flexible, and customizable manufacturing scheme. Among the various AM techniques, direct ink writing (DIW) has emerged as the most versatile 3D printing technique for the broadest range of materials. DIW allows printing of practically any material, as long as the precursor ink can be engineered to demonstrate appropriate rheological behavior. This technique acts as a unique pathway to introduce design freedom, multifunctionality, and stability simultaneously into its printed structures. Here, a comprehensive review of DIW of complex 3D structures from various materials, including polymers, ceramics, glass, cement, graphene, metals, and their combinations through multimaterial printing is presented. The review begins with an overview of the fundamentals of ink rheology, followed by an in‐depth discussion of the various methods to tailor the ink for DIW of different classes of materials. Then, the diverse applications of DIW ranging from electronics to food to biomedical industries are discussed. Finally, the current challenges and limitations of this technique are highlighted, followed by its prospects as a guideline toward possible futuristic innovations.

Direct Ink Writing: A 3D Printing Technology for Diverse Materials

Additive Manufacturing of Piezoelectric Materials

Preparation of high solid loading and low viscosity ceramic slurries for photopolymerization-based 3D printing

Along with extensive research on the three-dimensional (3D) printing of polymers and metals, 3D printing of ceramics is now the latest trend to come under the spotlight. The ability to fabricate ceramic components of arbitrarily complex shapes has been extremely challenging without 3D printing. This review focuses on the latest advances in the 3D printing of ceramics and presents the historical origins and evolution of each related technique. The main technical aspects, including feedstock properties, process control, post-treatments and energy source–material interactions, are also discussed. The technical challenges and advice about how to address these are presented. Comparisons are made between the techniques to facilitate the selection of the best ones in practical use. In addition, representative applications of the 3D printing of various types of ceramics are surveyed. Future directions are pointed out on the advancement on materials and forming mechanism for the fabrication of high-performance ceramic components.

3D printing of ceramics: A review

Mechanical properties and microstructures of 3D printed bulk cordierite parts

The invention discloses cordierite ceramic slurry for 3D printing and a preparation method thereof. The slurry comprises the following raw material components: cordierite ceramic powder, light-cured resin premix, a surfactant, a dispersant, and a photoinitiator. By metering with volume of cordierite ceramic powder, the slurry accounts for 40-60 parts and the premix accounts for 40 to 60 parts. Bymetering with mass percentage, the surfactant accounts for 1% to 3% of the cordierite ceramic powder, the dispersing agent accounts for 2% to 8% of the cordierite ceramic powder, and the photoinitiator accounts for 0.3% to 5% of the light-cured resin premix. The slurry has good dispersion stability, can be stored for a long time without being separated by precipitation under the condition of avoiding light, and can be directly used for light-cured 3D printing, the cordierite ceramic slurry for 3D printing provides a new printable ceramic material for 3D printing, and the invention also provides a new production technical scheme for the preparation and application of cordierite ceramic devices.

Cordierite ceramic slurry for 3D printing and preparation method thereof

The invention discloses a method for integrally preparing a cordierite honeycomb ceramic carrier by 3D printing. According to a relation between basic parameters and arrangement mode of through holesand pore density, specific surface area and open-cell rate of the cordierite honeycomb ceramic carrier, conventional parallel or special-shaped cross through holes in regular or irregular geometricalshape are utilized as microstructure of the porous ceramic carrier for design, and a porous honeycomb structure with high specific surface area and good mechanical properties is obtained; integrated design and 3D printing preparation of the cordierite honeycomb ceramic carrier are realized with a photocuring 3D printing technology; one integrated design and rapid preparation technique for micro and macro 3D structures of porous honeycomb ceramic parts is established.

Method for integrally preparing cordierite honeycomb ceramic carrier by 3D printing

The invention discloses a method for manufacturing a solid oxide fuel cell electrode by 3D ink jet printing, which comprises the following steps of: preparing a mixed solution of an electrode powder,a surfactant, a dispersant, a volatilization inhibitor, an acid-base regulator and a solvent as an electrode ink for 3D ink jet printing according to a predetermined percentage by mass; preparing a printing program according to the electrode structure to be prepared and inputting the print program into an ink-jet 3D printer; setting printing parameters of the inkjet 3D printer, including: pulse waveform, peak voltage, pulse frequency, substrate temperature, number of printing layers and single layer spacing; according to a set printing program and printing parameters, taking a pre-prepared electrolyte layer as a printing base, performing ink-jet 3D printing by using the electrode ink to obtain an electrode precursor, and placing the electrode precursor in an oven for drying; Solid oxide fuel cell electrodes are prepared by sintering the dried electrode precursor

Li Yang

Papers

3D printing of ceramics: A review

Mechanical properties and microstructures of 3D printed bulk cordierite parts

Cordierite ceramic slurry for 3D printing and preparation method thereof

Method for integrally preparing cordierite honeycomb ceramic carrier by 3D printing

A method for manufacturing a solid oxide fuel cell electrode by ink-jet 3D printing