Herein, we present a novel, binder-free, stereolithography-based 3D printing approach for fabricating complex sol-gel silica glassy structures at the centimeter scale using only sol-gel chemistry. Unlike conventional methods that rely on organic photopolymerizable resins or hybrid monomers, our process eliminates the need for sacrificial organic binders and the associated high temperature debinding steps. The proposed method utilizes a photo-base generator to induce a localized pH change upon irradiation, triggering spatially controlled sol-gel polymerization. After printing and rinsing, the resulting gel structures are transformed into mesoporous silica through low-temperature heat treatment at 250 ℃. The printed silica objects exhibit moderate transparency, minimal shrinkage (∼25 %), and a well-defined mesoporous structure with pore sizes predominantly in the 4-8 nm range. Solid-state ²⁹Si NMR spectroscopy and energy-dispersive X-ray spectroscopy confirm enhanced silica condensation under vacuum, achieving a near-theoretical Si:O atomic ratio. This approach enables the scalable production of binder-free, high-resolution silica objects with potential applications in optics, biomedical engineering, and microfluidics.

Soft robotics is a rapidly evolving field that leverages the unique properties of compliant, flexible materials to create robots that are capable of complex and adaptive behaviors. Unlike traditional rigid robots, soft robots rely on the properties of soft materials, which enable them to safely interact with humans, manipulate delicate objects, and perform various locomotion processes. This review provides a comprehensive overview of the development process of soft robots by additive manufacturing with a particular focus on the chemical aspects of the materials involved. The types of materials used in soft robotics, highlighting their properties, applications, and the role of their chemical composition in performance, are presented. The review then explores fabrication methods, detailing their chemical underpinnings, advantages, and limitations, followed by presenting common design methods used to optimize soft robots. Finally, the review discusses the diverse applications of soft robots across various domains, including medical, locomotion, manipulation, and wearable devices. By covering every stage of the additive manufactured soft robot, from material selection to application, this review aims to offer a deep and comprehensive understanding of this field.

Adhesives are vital in industries ranging from aerospace to consumer electronics. However, their reliance on non-recyclable polymers makes them suitable for one-time use and results in significant economic and environmental challenges. Reversible adhesives, based on covalent adaptable networks, address these issues and open possibilities for applications, including recyclable multi-layer packaging, removable labels, and fully recyclable electronics – batteries, smartphones, etc. Despite progress in dynamic and reversible bonds, current solutions often compromise performance or the ability to detach from substrates. This study proposes reversible high-performance adhesives that can undergo cycles of bonding-debonding without commonly reported need to add solvent, high-temperature processing or use deep-UV irradiation while maintaining adhesives' functionality and reducing environmental impact. The bonding is done by rapid photocuring, which occurs within 30 seconds under irradiation at a wide range of visible wavelengths (400–650 nm) while achieving constant adhesion strength across diverse substrates, including underwater adhesion. De-bonding is achieved using a simple household microwave. Furthermore, the adhesive's transparency and high refractive index enable its use in various optical applications, whereas its robustness in wet conditions expands its potential for bioadaptive or underwater systems. This adhesive represents a significant step toward sustainable adhesives that seamlessly integrate high performance with circular-economy principles.

Stereolithography printing of ceramics and glass relies on compositions containing dispersed particles in photopolymerizable solutions. A new approach based on utilizing sol–gel precursor solutions has been introduced in recent years, which overcomes challenges in particle-based printing compositions, such as light scattering, particle sedimentation, and high viscosity. Following sol–gel and photopolymerization processes’ combination, this paper presents the methodologies for the 3D printing of complex ceramics and glass structures. This combination allows precise structure control, enabling dense or porous objects, transparent forms, and simple doping. These advantages are presented through the fabrication of porous γ-alumina, transparent silica glass, and chromium-doped α-alumina.

This study explores the utilization of digital light processing (DLP) printing to fabricate complex structures using native gelatin as the sole structural component for applications in biological implants. Unlike approaches relying on synthetic materials or chemically modified biopolymers, this research harnesses the inherent properties of gelatin to create biocompatible structures. The printing process is based on a crosslinking mechanism using a di-tyrosine formation initiated by visible light irradiation. Formulations containing gelatin were found to be printable at the maximum documented concentration of 30 wt%, thus allowing the fabrication of overhanging objects and open embedded. Cell adhesion and growth onto and within the gelatin-based 3D constructs were evaluated by examining two implant fabrication techniques: (1) cell seeding onto the printed scaffold and (2) printing compositions that contain cells (cell-laden). The preliminary biological experiments indicate that both the cell-seeding and cell-laden strategies enable making 3D cultures of chondrocytes within the gelatin constructs. The mechanical properties of the gelatin scaffolds have a compressive modulus akin to soft tissues, thus enabling the growth and proliferation of cells, and later degrade as the cells differentiate and form a grown cartilage. This study underscores the potential of utilizing non-modified protein-only bioinks in DLP printing to produce intricate 3D objects with high fidelity, paving the way for advancements in regenerative tissue engineering.

The additive manufacturing of hardmetals has attracted great attention recently but faces significant challenges in low printing resolution and low mechanical strength. Herein, the fabrication of hardmetal parts with complex structures and high surface quality by vat photopolymerization assisted with a sintering process has been achieved. This was enabled by in situ polymerization-induced microencapsulation of WC powder, which simultaneously enhances the photocuring ability and sedimentation stability of the WC-Co slurry. The WC powder is microencapsulated by a polystyrene (PS, WC@PS) coating with a thickness of ∼20 nm. The curing depth of the WC-Co slurry with WC@PS was dramatically increased from 32 to 336 μm compared to the slurry with original WC, exhibiting an average increment of 650%. The 3D-printed hardmetal parts exhibited a relative density of 99.5%, a Rockwell hardness of 86.9 HRA, and a surface roughness R_a of 2.26 μm, approaching the theoretical limits in classical powder metallurgy-derived WC-Co hardmetal parts. With high density and hardness, it is shown that a printed drilling bit can easily drill through metal sheets. This work paves a path for the vat photopolymerization 3D printing of miniature complex hardmetal components combined with high surface quality and high performance.

Stereolithography printing of ceramics and glass relies on compositions containing dispersed particles in photopolymerizable solutions. A new approach based on utilizing sol–gel precursor solutions has been introduced in recent years, which overcomes challenges in particle-based printing compositions, such as light scattering, particle sedimentation, and high viscosity. Following sol–gel and photopolymerization processes’ combination, this paper presents the methodologies for the 3D printing of complex ceramics and glass structures. This combination allows precise structure control, enabling dense or porous objects, transparent forms, and simple doping. These advantages are presented through the fabrication of porous γ-alumina, transparent silica glass, and chromium-doped α-alumina.

Printed electronics is based on the application of 2D and 3D printing technologies to fabricate electronic devices. To fabricate the printed electronic 2D and 3D devices with the required performance, it is necessary to properly select and tailor the conductive inks, which are often composed of nanomaterials, The main nanomaterials in conductive inks for 2D and 3D printed electronics contain conductive nanomaterials such as metal nanoparticles (NPs) and nanowires and carbon based nanomaterials: carbon black, graphene sheets, and carbon nanotubes (CNTs). All these materials were successfully applied for the fabrication of various electronic devices such as electrical circuits, transparent electrodes, flexible thin film transistors, RFID antennas, photovoltaic devices, and flexible touch panels. In this paper, we focus on the basic properties of these nanomaterials, in view of their application in conductive inks, on obtaining conductive patterns by 2D and 3D printing, and on various methods of post-printing treatment. In the last section, a perspective on future needs and applications will be presented, including emerging technologies.

The growing demand for dexterous and autonomous robotic manipulation highlights the need for advanced sensing and control strategies, particularly for slip prevention. Although soft grippers provide intrinsic compliance and adaptability, their effectiveness is often limited by the lack of real-time sensory feedback and the complexity of soft actuator dynamics. Inspired by human tactile perception, we developed a bioarchitectonics-inspired soft slip sensor with a three-dimensional structure that leverages crack and stress concentration to enhance sensitivity to incipient slip and shear force. Complementarily, a soft gripper with a linear pressure-to-force response was engineered to enable stable and predictable force modulation. The flexible slip sensors were conformally integrated onto the grippers, forming a fully perceptive soft robotic system capable of detecting early-stage slippage and investigating interfacial frictional properties. This integration establishes a closed-loop sensorimotor framework that notably improves the reliability and adaptability of soft robotic grasping across a wide range of real-world applications.

Technological advancements drive the demand for smart, flexible, and sustainable devices capable of integration into daily life. Pressure sensors, particularly those utilizing halide perovskites, face key challenges in sensitivity, stability, and integration with soft systems. This study focuses on the investigation of quasi-two-dimensional (2D) perovskite pressure sensors, where the perovskite is embedded within a polyvinylidene fluoride (PVDF) polymer matrix and protected by a polydimethylsiloxane (PDMS) polymer layer. The improvement in the performance of the pressure sensors is achieved through the optimization of the solvent composition, perovskite:PVDF ratio, and thickness of the PDMS layer, with a deep understanding of the morphological structure's influence on piezoelectric properties. Our perovskite layer achieves a high piezoelectric coefficient (d₃₃) of 31.26 pm V⁻¹, surpassing previously reported values for halide perovskites. Unlike previous studies, we systematically investigate the correlation between the PDMS thickness and the piezoelectric response, identifying a critical thickness threshold (∼23 μm) beyond which sensing is suppressed. The devices demonstrate pressure sensitivity in the absence of any external power source and maintain reliable performance for 1000 cycles and up to 60 days under ambient conditions. Successful integration of the sensors into soft robotic grippers while also demonstrating sensitivity to various weights highlights their potential for application in fields such as soft robotics and healthcare.

Adjustable wettability is important for various fields, such as droplet manipulation and controlled surface adhesion. Herein, we present high-resolution 3D stretchable structures with tunable superhydrophobicity, fabricated by a stereolithography-based printing process. The printing compositions comprise nonfluorinated monomers based on silicone urethane with dispersed hydrophobic silica particles. 3D lotus-like structures were designed and printed, having microsize pillars located at the external surfaces, with controlled dimensions and interspacing. The design of the pillars and the presence of the hydrophobic silica particles resulted in superhydrophobicity due to the surface structuring and entrapment of air between the pillars. The best structures display a contact angle of 153.3° ± 1.3° and rolling angle of 3.3° ± 0.5°, and their self-cleaning, water repellency, and buoyancy are demonstrated. The durability of the structure over time, water immersion, and heat exposure were tested, confirming the preservation of superhydrophobicity under these conditions. Upon stretching the surfaces, the interpillar distances change, thus enabling tuning the wetting properties and achieving good control over the contact and rolling angles, while the stretching-induced superhydrophobicity is reversible. This approach can expand the potential applications of superhydrophobic soft materials to fields requiring control over the wetting properties, including soft robotics, biomedical devices, and stretchable electronics.

A novel approach, i.e., Continuous Material Deposition on Filaments (CMDF), for the incorporation of active materials within 3D-printed structures is presented. It is based on passing a filament through a solution in which the active material is dissolved together with the polymer from which the filament is made. This enables the fabrication of a variety of functional 3D-printed objects by fused deposition modeling (FDM) using commercial filaments without post-treatment processes. This generic approach has been demonstrated in objects using three different types of materials, Rhodamine B, ZnO nanoparticles (NPs), and Ciprofloxacin (Cip). The functionality of these objects is demonstrated through strong antibacterial activity in ZnO NPs and the controlled release of the antibiotic Cip. CMDF does not alter the mechanical properties of FDM-printed structures, can be applied with any type of FDM printer, and is, therefore, expected to have applications in a wide variety of fields.

Piezoelectric materials have found widespread use in miniaturized sensors and actuators due to their ability of mutual conversion of mechanical and electric energy. However, current fabrication techniques for these materials are limited to either bulky structures or thin films, restricting the potential that could arise from developing devices with more intricate geometries. Here, we have developed particle-free piezoelectric ink and successfully employed in 3D printing complex barium titanate (BTO) devices using Digital Light Processing technology. The sol–gel process overcomes the viscosity and light scattering issues associated with the slurry traditionally used in 3D printing of piezoelectric ceramic materials. Printed BTO exhibits a remarkable piezoelectric coefficient of 50 pm/V and is utilized to create 3D micrometric structures for applications as both active devices, such as actuators, and passive devices, including displacement sensors and energy harvesters. Furthermore, the flexibility in device fabrication enabled us to 3D print metamaterial piezoelectric structures, designed to concentrate mechanical stress, thereby enhancing the electrical response compared to conventional bulk structures. This research not only advances the field by overcoming fabrication challenges but also opens avenues for creating innovative devices. The design freedom afforded by additive manufacturing technology further underscores the potential for groundbreaking developments in this domain.

Many optoelectronic devices, such as solar cells and LEDs, require materials that possess both transparency and conductivity. Indium tin oxide (ITO), the most commonly used transparent conductor, is limited to flat thin films and, therefore, cannot be used in 3D electronics. Herein, we present the fabrication of complex 3D ITO structures at sub-micron resolution via multiphoton absorption polymerization (MAP), a vat photopolymerization technology, by combining sol-gel chemistry and radical polymerization. Following the MAP fabrication, heat treatment is applied to convert the gel into a ceramic ITO. The sintering temperature affects the porosity, electrical conductivity, and transparency of the printed ITO structures. Electrical conductivity was measured for printed objects sintered at temperatures starting at 700 °C up to 1150 °C with a maximum bulk conductivity of 14.47 ± 1.54 S/cm at 1000 °C and maximal transparency above 90 %. Enabling the fabrication of full 3D conductive ITO micro-structures via MAP, this work unlocks new possibilities and perspectives for the fabrication of 3D optoelectronic devices with transparent and conductive components.

Traditional printing compositions for stereolithography (SLA), a vat photopolymerization technology, rely on light-sensitive photoinitiators (PIs) to initiate cross-linking reactions. Here, we propose a new approach for printing in which the polymerisation occurs locally with carbon nanotubes (CNTs), which function as photothermal converters combined with low-cost thermal initiators (TIs). The irradiation is performed at near-infrared (NIR), which enables deep light penetration, and polymerisation in black compositions, thus increasing the printing throughput. We demonstrate the control over polymerisation kinetics, printing resolution and cure depth, achieving very large printable layer thickness. The CNT photoconvertors can be used in both nonaqueous and aqueous systems, while the latter addresses the limited availability of water-soluble PIs for printing in water. The CNT enables dual use, initiating polymerisation and printing composite materials. This approach presents an advancement in SLA-based technologies, avoiding the use of conventional PIs and thus broadening the scope of 3D printing applications.

A novel method is presented for fabricating 3D-printed Cr³⁺-doped α-Al₂O₃ complex structures, known as Ruby, using digital light processing (DLP) 3D printing and sol-gel reactions based on solutions only. The aqueous printing solution comprises aluminum and chromium chloride as the sol-gel precursor and acrylic acid (AA) as the polymerizable component. After photopolymerization, aging, and sintering at 1150°C, structures shrink up to 28±7%, achieving a final printing resolution of 55.7±0.7 μm, surpassing the nominal printer’s resolution of 200 μm. Characterization includes X-ray diffraction, scanning electron microscopy, UV-Vis, and fluorescence measurements, revealing crystalline Cr:α-Al₂O₃ composition emitting at 693 nm. The structures exhibit maximum compression stress of 89±3 MPa and microhardness of 340-500 HV, showcasing potential applications in thermal insulation, jewelry, and mechanical uses.

Rapid deployment of automation in today's world has opened up exciting possibilities in the realm of design and fabrication of soft robotic grippers endowed with sensing capabilities. Herein, a novel design and rapid fabrication by 3D printing of a mechano-optic force sensor with a large dynamic range, sensitivity, and linear response, enabled by metamaterials-based structures, is presented. A simple approach for programming the metamaterial's behavior based on mathematical modeling of the sensor under dynamic loading is proposed. Machine learning models are utilized to predict the complete force–deformation profile, encompassing the linear range, the onset of nonlinear behavior, and the slope of profiles in both bending and compression-dominated regions. The design supports seamless integration of the sensor into soft grippers, enabling 3D printing of the soft gripper with an embedded sensor in a single step, thus overcoming the tedious and complex and multiple fabrication steps commonly applied in conventional processes. The sensor boasts a fine resolution of 0.015 N, a measurement range up to 16 N, linearity (adj. R²–0.991), and delivers consistent performance beyond 100 000 cycles. The sensitivity and range of the embedded mechano-optic force sensor can be easily programmed by both the metamaterial structure and the material's properties.

Soft grippers are garnering increasing attention for their adeptness in conforming to diverse objects, particularly delicate items, without warranting precise force control. This attribute proves especially beneficial in unstructured environments and dynamic tasks such as food handling. Human hands, owing to their elevated dexterity and precise motor control, exhibit the ability to delicately manipulate complex food items, such as small or fragile objects, by dynamically adjusting their grasping configurations. Furthermore, with their rich sensory receptors and hand-eye coordination that provide valuable information involving the texture and form factor, real-time adjustments to avoid damage or spill during food handling appear seamless. Despite numerous endeavors to replicate these capabilities through robotic solutions involving soft grippers, matching human performance remains a formidable engineering challenge. Robotic competitions serve as an invaluable platform for pushing the boundaries of manipulation capabilities, simultaneously offering insights into the adoption of these solutions across diverse domains, including food handling. Serving as a proxy for the future transition of robotic solutions from the laboratory to the market, these competitions simulate real-world challenges. Since 2021, our research group has actively participated in RoboSoft competitions, securing victories in the Manipulation track in 2022 and 2023. Our success was propelled by the utilization of a modified iteration of our Retractable Nails Soft Gripper (RNSG), tailored to meet the specific requirements of each task. The integration of sensors and collaborative manipulators further enhanced the gripper’s performance, facilitating the seamless execution of complex grasping tasks associated with food handling. This article encapsulates the experiential insights gained during the application of our highly versatile soft gripper in these competition environments.

Hybrid perovskites show piezoelectric properties due to polarization and centro-symmetry breaking of PbX₆ pyramids (X = I-, Br-, Cl-). This study examines the piezoelectric response of quasi-2D perovskites using various barrier molecules: benzyl amine (BzA), phenylethyl amine (PEA), and butyl diamine (BuDA). Utilizing piezoelectric force microscopy measurements, we determine the piezoelectric coefficient (d₃₃) where BuDA exhibits a substantial response with values of 147 pm V^–1 for n = 5, better than the other quasi-2D and 3D perovskite counterparts. Density functional theory calculations reveal distorted bond angles in the PbBr₆ pyramids for quasi-2D perovskites, enhancing symmetry breaking. Additionally, polarizabilities and dielectric constants, derived from ab initio many-body perturbation theory, are highest for BuDA, followed by PEA and BzA, aligning with experimental results. We demonstrate pressure sensor performance, emphasizing the quicker capacitance decay time of the quasi-2D perovskite based on BuDA. This research underscores the impact of perovskite dimensionality on piezoelectricity, paving the way for the development of sensitive and wide-ranging pressure sensors.