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Short‐wave infrared (SWIR) image sensors based on colloidal quantum dots (QDs) are characterized by low cost, small pixel pitch, and spectral tunability. Adoption of QD‐SWIR imagers is, however, hampered by a reliance on restricted elements such as Pb and Hg. Here, QD photodiodes, the central element of a QD image sensor, made from non‐restricted In(As,P) QDs that operate at wavelengths up to 1400 nm are demonstrated. Three different In(As,P) QD batches that are made using a scalable, one‐size‐one‐batch reaction and feature a band‐edge absorption at 1140, 1270, and 1400 nm are implemented. These QDs are post‐processed to obtain In(As,P) nanocolloids stabilized by short‐chain ligands, from which semiconducting films of n‐In(As,P) are formed through spincoating. For all three sizes, sandwiching such films between p‐NiO as the hole transport layer and Nb:TiO2 as the electron transport layer yields In(As,P) QD photodiodes that exhibit best internal quantum efficiencies at the QD band gap of 46±5% and are sensitive for SWIR light up to 1400 nm. A complete process flow to form photodiode stacks sensitive for short‐wave infrared (SWIR) light based on non‐restricted In(As,P) quantum dots (QDs) is proposed. Films made of semiconducting n‐In(As,P) QDs inks, formulated through apolar/polar QD phase transfer, form a rectifying junction with p‐NiO that is photosensitive beyond 1400 nm. This result highlights the prospect of printable SWIR opto‐electronics based on InAs QDs.

Printing electronics incorporates several significant technologies, such as semiconductor devices produced by various printing techniques on flexible substrates. With the growing interest in printed electronic devices, new technologies have been developed to make novel devices with inexpensive and large-area printing techniques. This review article focuses on the most recent developments in printed photonic devices. Photonics and optoelectronic systems may now be built utilizing materials with specific optical properties and 3D designs achieved through additive printing. Optical and architected materials that can be printed in their entirety are among the most promising future research topics, as are platforms for multi-material processing and printing technologies that can print enormous volumes at a high resolution while also maintaining a high throughput. Significant advances in innovative printable materials create new opportunities for functional devices to act efficiently, such as wearable sensors, integrated optoelectronics, and consumer electronics. This article provides an overview of printable materials, printing methods, and the uses of printed electronic devices.

Confining photons in a finite volume is highly desirable in modern photonic devices, such as waveguides, lasers and cavities. Decades ago, this motivated the study and application of photonic crystals, which have a photonic bandgap that forbids light propagation in all directions 1 – 3 . Recently, inspired by the discoveries of topological insulators 4 , 5 , the confinement of photons with topological protection has been demonstrated in two-dimensional (2D) photonic structures known as photonic topological insulators 6 – 8 , with promising applications in topological lasers 9 , 10 and robust optical delay lines 11 . However, a fully three-dimensional (3D) topological photonic bandgap has not been achieved. Here we experimentally demonstrate a 3D photonic topological insulator with an extremely wide (more than 25 per cent bandwidth) 3D topological bandgap. The composite material (metallic patterns on printed circuit boards) consists of split-ring resonators (classical electromagnetic artificial atoms) with strong magneto-electric coupling and behaves like a ‘weak’ topological insulator (that is, with an even number of surface Dirac cones), or a stack of 2D quantum spin Hall insulators. Using direct field measurements, we map out both the gapped bulk band structure and the Dirac-like dispersion of the photonic surface states, and demonstrate robust photonic propagation along a non-planar surface. Our work extends the family of 3D topological insulators from fermions to bosons and paves the way for applications in topological photonic cavities, circuits and lasers in 3D geometries. A three-dimensional photonic topological insulator is presented, made of split-ring resonators with strong magneto-electric coupling, which has an extremely wide topological bandgap, forbidding light propagation.

Topological photonics has revolutionized our understanding of light propagation, providing a robust way to manipulate light. So far, most of studies in this field are focused on designing a static photonic structure. Developing a dynamic photonic topological platform to switch multiple topological functionalities at ultrafast speed is still a great challenge. Here we theoretically propose and experimentally demonstrate a reprogrammable plasmonic topological insulator, where the topological propagation route can be dynamically changed at nanosecond-level switching time, leading to an experimental demonstration of ultrafast multi-channel optical analog-digital converter. Due to the innovative use of electric switches to implement the programmability of plasmonic topological insulator, each unit cell can be encoded by dynamically controlling its digital plasmonic states while keeping its geometry and material parameters unchanged. Our reprogrammable topological plasmonic platform is fabricated by the printed circuit board technology, making it much more compatible with integrated photoelectric systems. Furthermore, due to its flexible programmability, many photonic topological functionalities can be integrated into this versatile topological platform. The development of fast and dynamic topological photonic platforms is an ongoing challenge. Here, the authors demonstrate a reprogrammable plasmonic topological insulator in which ultrafast electric switches allow for nanosecond-level switching time between different configurations.

The incorporation of nanomaterials has revolutionized the field of additive manufacturing. The combination of additive manufacturing technology with nanomaterials has significantly broadened the scope of materials available for modern and innovative applications in various fields, including healthcare, construction, food processing, and the textile industry. By integrating nanomaterials into additive manufacturing, the manufacturing process can be enhanced, and the properties of materials can be improved, enabling the fabrication of intricate structures and complex shapes. This review provides a comprehensive overview of the latest research on additive manufacturing techniques that utilize nanomaterials. It covers a wide range of nanomaterials employed in additive manufacturing and presents recent research findings on their incorporation into various categories of additive manufacturing, highlighting their impact on the properties of the final product. Moreover, the article discusses the potential of nanomaterial-based additive manufacturing technologies to revolutionize the manufacturing industry and explores the diverse applications of these techniques. The review concludes by outlining future research directions and focusing on addressing current challenges to enhance the overall efficiency and effectiveness of nanomaterial-based additive manufacturing. Graphical abstract

Digital cameras with layouts inspired by the compound, hemispherical designs of arthropod eyes have been built by combining elastomeric optical elements with deformable arrays of thin silicon photodetectors. Look around you: insect-inspired cameras The eyes of insects and other arthropods provide intriguing models for camera designers to imitate. Here John Rogers and colleagues describe a new technique for building a hemispherical camera that takes its design cues from the eyes of fire ants and bark beetles. The new device is almost fully hemispherical and features 180 imaging elements, providing a 160-degree field of view. The camera combines elastomeric compound optical elements with deformable arrays of thin-film silicon photodetectors, in co-integrated sheets that can be moulded into hemispherical shapes. Potential applications range from advanced surveillance cameras to miniaturized endoscopes. In arthropods, evolution has created a remarkably sophisticated class of imaging systems, with a wide-angle field of view, low aberrations, high acuity to motion and an infinite depth of field 1 , 2 , 3 . A challenge in building digital cameras with the hemispherical, compound apposition layouts of arthropod eyes is that essential design requirements cannot be met with existing planar sensor technologies or conventional optics. Here we present materials, mechanics and integration schemes that afford scalable pathways to working, arthropod-inspired cameras with nearly full hemispherical shapes (about 160 degrees). Their surfaces are densely populated by imaging elements (artificial ommatidia), which are comparable in number (180) to those of the eyes of fire ants ( Solenopsis fugax ) and bark beetles 4 , 5 ( Hylastes nigrinus ). The devices combine elastomeric compound optical elements with deformable arrays of thin silicon photodetectors into integrated sheets that can be elastically transformed from the planar geometries in which they are fabricated to hemispherical shapes for integration into apposition cameras. Our imaging results and quantitative ray-tracing-based simulations illustrate key features of operation. These general strategies seem to be applicable to other compound eye devices, such as those inspired by moths and lacewings 6 , 7 (refracting superposition eyes), lobster and shrimp 8 (reflecting superposition eyes), and houseflies 9 (neural superposition eyes).

Near-zero-index (NZI) media, a medium with near zero permittivity and/or permeability, exhibits unique wave phenomena and exciting potential for multiple applications. However, previous proof-of-concept realizations of NZI media based on bulky and expensive platforms are not easily compatible with low-cost and miniaturization demands. Here, we propose the method of substrate-integrated (SI) photonic doping, enabling the implementation of NZI media within a printed circuit board (PCB) integrated design. Additionally, the profile of the NZI device is reduced by half by using symmetries. We validate the concept experimentally by demonstrating NZI supercoupling in straight and curve substrate integrated waveguides, also validating properties of position-independent photonic doping, zero-phase advance and finite group delay. Based on this platform, we propose design of three NZI devices: a high-sensitivity dielectric sensor, an efficient acousto-microwave modulator, and an arbitrarily-curved ‘electric fiber’. Our results represent an important step forward in the development of NZI technologies for microwave/terahertz applications. Here, the authors demonstrate substrate-integrated photonic doping, enabling the implementation of near-zero-index media within a printed circuit board integrated design. They illustrate the potential by designing and numerically demonstrating a dielectric sensor, an acousto-microwave modulator and a flexible transmission line.

Photonic integrated circuits (PICs) represent a promising technology for the much-needed medical devices of today. Their primary advantage lies in their ability to integrate multiple functions onto a single chip, thereby reducing the complexity, size, maintenance requirements, and costs. When applied to optical coherence tomography (OCT), the leading tool for state-of-the-art ophthalmic diagnosis, PICs have the potential to increase accessibility, especially in scenarios, where size, weight, or costs are limiting factors. In this paper, we present a PIC-based CMOS-compatible spectrometer for spectral domain OCT with an unprecedented level of integration. To achieve this, we co-integrated a 512-channel arrayed waveguide grating with electronics. We successfully addressed the challenge of establishing a connection from the optical waveguides to the photodiodes monolithically co-integrated on the chip with minimal losses achieving a coupling efficiency of 70%. With this fully integrated PIC-based spectrometer interfaced to a spectral domain OCT system, we reached a sensitivity of 92dB at an imaging speed of 55kHz, with a 6dB signal roll-off occurring at 2mm. We successfully applied this innovative technology to obtain 3D in vivo tomograms of zebrafish larvae and human skin. This ground-breaking fully integrated spectrometer represents a significant step towards a miniaturised, cost-effective, and maintenance-free OCT system.

This review article provides a comprehensive analysis of the photonic sintering conditions necessary to process non-oxide ceramics, to obtain similar material properties when compared with those of thermally annealed ones, for various applications in printed electronics. This article presents a thorough examination of the scientific literature on this topic, discussing the principles of photonic sintering applied to non-oxide ceramics, its advantages over traditional post-processing methods, and a quantitative overview of the performance of devices fabricated with the crystalline materials obtained.

Printed electronics currently holds a significant share in the electronics fabrication market due to advantages in high-throughput production and customizability in terms of material support and system process. The printing of traces and interconnects, passive and active components such as resistors, capacitors, inductors, and application-specific electronic devices, have been a growing focus of research in the area of additive manufacturing. Adaptation of new 3D-printing technologies and manufacturing methods, specifically for printed electronics, are potentially transformative in flexible electronics, wireless communications, efficient batteries, solid-state display technologies, etc. Other than printing new and reactive functional electronic materials, the functionalization of the printing substrates with unusual geometries apart from the conventional planar circuit boards will be a challenge. Building the substrate, printing the conductive tracks, pick-and-placing or embedding the electronic components, and interconnecting them, are fundamental fabrication protocols new 3D-printing systems should adopt for a more integrated fabrication. Moreover, designers and manufacturers of such systems will play an important role in scaling 3D-printed electronics from prototyping to high-throughput mass production. This review gives a groundwork for such understanding, defining methods and protocols, reviewing various 3D-printing methods, and describing the state-of-the-art in 3D-printed electronics and their future growth.