Abstract Four-dimensional (4D) printing is an advanced manufacturing technology that has rapidly emerged as a transformative tool with the capacity to reshape various research domains and industries. Distinguished by its integration of time as a dimension, 4D printing allows objects to dynamically respond to external stimuli, setting it apart from conventional 3D printing. This roadmap has been devised, by contributions of 44 active researchers in this field from 32 affiliations world-wide, to navigate the swiftly evolving landscape of 4D printing, consolidating recent advancements and making them accessible to experts across diverse fields, ranging from biomedicine to aerospace, textiles to electronics. The roadmap’s goal is to empower both experts and enthusiasts, facilitating the exploitation of 4D printing’s transformative potential to create intelligent, adaptive objects that are not only feasible but readily attainable. By addressing current and future challenges and proposing advancements in science and technology, it sets the stage for revolutionary progress in numerous industries, positioning 4D printing as a transformative tool for the future.

The growing demand for efficient energy storage systems, particularly in portable electronics and electric vehicles, has led to increased interest in supercapacitors, which offer high power density, rapid charge/discharge rates, and long cycle life. However, improving their energy density without compromising performance remains a challenge. In this study, we developed novel 3D-printed reduced graphene oxide (rGO) electrodes coated with polyaniline (PANI) to enhance their electrochemical properties. The rGO 3D-printed electrodes were fabricated using direct ink writing (DIW), which allowed precise control over thickness, ranging from 4 to 24 layers. A unique ink formulation was optimized for the printing process, consisting of rGO, cellulose acetate (CA) as a binder, and acetone as a solvent. The PANI coating was applied via chemical oxidative polymerization (COP) with up to five deposition cycles. Electrochemical testing, including cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS), revealed that 12-layer electrodes with three PANI deposition cycles achieved the highest areal capacitance of 84.32 mF/cm2. While thicker electrodes (16 layers and beyond) experienced diminished performance due to ion diffusion limitations, the composite electrodes demonstrated excellent cycling stability, retaining over 80% of their initial capacitance after 1500 cycles. This work demonstrates the potential of 3D-printed PANI/rGO electrodes for scalable, high-performance supercapacitors with customizable architectures.

Building 3D electrospun macrostructures and monitoring the biological activities inside them are challenging. In this study, 3D fibrous polycaprolactone (PCL) macrostructures were successfully fabricated using in-house 3D electrospinning. The main factors supporting the 3D self-assembled nanofiber fabrication are the H3PO4 additives, flow rate, and initial distance. The effects of solution concentration, solvent, H3PO4 concentration, flow rate, initial distance, voltage, and nozzle speed on the 3D macrostructures were examined. The optimal conditions of 4 mL/h flow rate, 4 cm initial nozzle-collector distance, 14 kV voltage, and 1 mm/s nozzle speed provided a rapid buildup of cylinder macrostructures with 6 cm of diameter, reaching a final height of 16.18 ± 2.58 mm and a wall thickness of 3.98 ± 1.01 mm on one perimeter with uniform diameter across different sections (1.40 ± 1.10 μm average). Oxygen plasma treatment with 30-50 W for 5 min significantly improved the hydrophilicity of the PCL macrostructures, proving a suitable scaffold for in vitro cell cultures. Additionally, 3D images obtained by synchrotron radiation X-ray tomographic microscopy (SRXTM) presented cell penetration and cell growth within the scaffolds. This breakthrough in 3D electrospinning surpasses current scaffold fabrication limitations, opening new possibilities in various fields.

Abstract Photocatalysis has emerged as a promising method for wastewater treatment, organic removal, and hydrogen gas production. Titanium dioxide (TiO2) is a popular photocatalyst due to its ability to absorb ultraviolet light, its electronic structure, and its optical and chemical stability. The photocatalytic capacity of TiO2 is influenced by its crystal structure (anatase, rutile, and brookite), particle size, and surface area, which can be optimized. Moreover, TiO2 can be coated onto substrates such as ceramics or polymers. This research aims to investigate the application of 3D printing techniques to fabricate composites between TiO2 and polyaniline (PANI) under controlled processing conditions. The 3D photocatalyst was characterized using XRD, SEM, XAS, FTIR, and UV-VIS techniques. The results of this research could pave the way for more efficient and effective photocatalysts fabricated by 3D printing technique, with potential benefits for environmental sustainability and energy production.

Cancer is a critical cause of global human death. Not only are complex approaches to cancer prognosis, accurate diagnosis, and efficient therapeutics concerned, but post-treatments like postsurgical or chemotherapeutical effects are also followed up. The four-dimensional (4D) printing technique has gained attention for its potential applications in cancer therapeutics. It is the next generation of the three-dimensional (3D) printing technique, which facilitates the advanced fabrication of dynamic constructs like programmable shapes, controllable locomotion, and on-demand functions. As is well-known, it is still in the initial stage of cancer applications and requires the insight study of 4D printing. Herein, we present the first effort to report on 4D printing technology in cancer therapeutics. This review will illustrate the mechanisms used to induce the dynamic constructs of 4D printing in cancer management. The recent potential applications of 4D printing in cancer therapeutics will be further detailed, and future perspectives and conclusions will finally be proposed.

We report the development and characterization of a detection technique for scattering-type scanning near-field optical microscopy (s-SNOM) that enables near-field amplitude and phase imaging at two or more wavelengths simultaneously. To this end, we introduce multispectral pseudoheterodyne (PSH) interferometry, where infrared lasers are combined to form a beam with a discrete spectrum of laser lines and a time-multiplexing scheme is employed to allow for the use of a single infrared detector. We first describe and validate the implementation of multispectral PSH into a commercial s-SNOM instrument. We then demonstrate its application for the real-time correction of the negative phase contrast (NPC), which provides reliable imaging of weak IR absorption at the nanoscale. We anticipate that multispectral PSH could improve data throughput, reduce effects of sample and interferometer drift, and help to establish multicolor s-SNOM imaging as a regular imaging modality, which could be particularly interesting as new infrared light sources become available.

Four-dimensional (4D) printing has received growing interests in healthcare with advancements in individualized dynamic constructs, including controllable shape transformation or triggerable function upon exposure to stimuli. It is emerging as a technology that can play a critical role in aiding cancer treatments, with potential abilities of shape, function, or property changes, facilitating personalized medicine for localized cancer treatments. Here, smart materials used in 4D printed approaches are presented to explore their purpose and utilities in aiding cancer therapeutic approaches. To guide 4D printed materials in various perspectives, recently reported progress on applications of using 3D and 4D printing in aiding cancer treatments and tools, such as hyperthermia, drug delivery systems for chemotherapy, and pharmaceutical models of cancer management, is discussed. Lastly, the challenges and future visions of 4D printing research are proposed.

Vat photopolymerization 3D printing, including LCD 3D printing, is a versatile method for the fabrication of complex structures with numerous applications. The aim of this study was to investigate the potential of graphene nanoplatelets (GNP) as an additive for improving the mechanical properties of carbon-filled composite resin for LCD 3D printing. Tensile testing was conducted on the 3D-printed samples using the ASTM D638 type V standard model. The results indicated that adding 0.1% w/w GNP with 20 sec of exposure time increased the elastic modulus of the specimen from 7.31±1.02 MPa to 9.38±0.37 MPa for x-orientation (horizontal) and from 7.62±0.93 MPa to 9.58±0.61 MPa for y-orientation (vertical). Furthermore, the maximum tensile strength increased from 3.87±1.13 MPa to 5.28±0.73 MPa for y-orientation and from 4.06±0.92 MPa to 5.49±0.49 MPa for x-orientation. These results demonstrate the efficacy of GNP as an effective additive for enhancing the mechanical properties of carbon-based composite resin in LCD 3D printing.

In this study, we explored the technical feasibility to fabricate bi-material structures having electrically conductive properties at the surface using a conventional digital light processing (DLP) by printing conductive resin containing multiwalled carbon nanotube (MWCNT) on the non-conductive one. It was found that the DLP-printed bi-material structure with conductive surface cooperated with 1.35 wt% of MWCNT offers electrical resistance in the range of 7.58 ± 0.46 megaohm. The bi-material structure possessed bending yield stress of 6 MPa. When applying 12-V DC for 1 h at the surface of the printed structure, it showed an excellent antimicrobial activity in which more than 99.99% of Eschericia coli and Staphylococcus aureus was destroyed. This novel disinfecting approach has advantages over other conventional sterilizations, such as volatile solvent and autoclave sterilization, because it is solvent-free, fast, and less labor-consuming. The developed technology may be applicable to retrofit antimicrobial printed surfaces on existing designs. Graphical abstract

A high piezoelectric coefficient polymer and biomaterial for bone tissue engineering— poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)—has been successfully fabricated into 3D scaffolds using the wet electrospinning method. Three-dimensional (3D) scaffolds have significant advantages for tissue engineering applications. Electrospinning is an advanced method and can fabricate 3D scaffolds. However, it has some limitations and is difficult to fabricate nanofibers into 3D shapes because of the low controllability of porosity and internal pore shape. The PVDF-HFP powders were dissolved in a mixture of acetone and dimethylformamide with a ratio of 1:1 at various concentrations of 10, 13, 15, 17, and 20 wt%. However, only the solutions at 15 and 17 wt% with optimized electrospinning parameters can be fabricated into biomimetic 3D shapes. The produced PVDF-HFP 3D scaffolds are in the cm size range and mimic the structure of the natural nests of termites of the genus Apicotermes. In addition, the 3D nanofiber-based structure can also generate more electrical signals than the conventional 2D ones, as the third dimension provides more compression. The cell interaction with the 3D nanofibers scaffold was investigated. The in vitro results demonstrated that the NIH 3T3 cells could attach and migrate in the 3D structures. While conventional electrospinning yields 2D (flat) structures, our bio-inspired electrospun termite nest-like 3D scaffolds are better suited for tissue engineering applications since they can potentially mimic native tissues as they have biomimetic structure, piezoelectric, and biological properties.

The small diameter artificial blood vessel is synthesized with a diameter less than or equal to 6 millimetres. This technique has been used in coronary artery bypass grafting to treat coronary artery disease. Currently, the problem of coronary artery disease is still common, in addition to aortic aneurysm caused by the incompatibility of mechanical properties between the artificial blood vessel and the local blood vessel in the patient’s body. This research aims to solve the aforementioned problems using electrospinning and 3D printing technologies, as many types of materials are supported, all parameters are easy to change, and the cost is low. In this report, we describe a design for a small diameter polylactic acid (PLA) vascular graft fabricated by electrospinning with solutions of PLA in AC/DMF (1:1) 10, 12 and 15% w/v at 4 mm. The electrospun PLA nanofibers are tested for their morphology, contact angle, and seam strength. As the results, the fibres are still no same direction alignment due to insufficient rotation speed. The filament holding force is in the range of 1.90-2.71 N and the contact angles are greater than 90° because the samples are not wettable and have hydrophobic property. Further on, we will investigate other required properties, such as cell culture and other mechanical properties. Furthermore, we will compare the results with 3D printed artificial blood vessels with small diameter.

Fabrication of macroscopic three-dimensional (3D) structures made of nanofibers of widely used polymers is reported. 3D structures have several benefits over conventional flat two-dimensional (2D) structures by the added dimension. The structures have been fabricated by the 3D electrospinning technology that can build 3D structures rapidly due to certain additives in the solution and appropriate process conditions. The process parameters of 3D electrospinning have been identified and investigated to better understand the formation mechanism of the 3D build-up for polystyrene (PS), polyacrylonitrile (PAN), and polyvinylpyrrolidone (PVP). Different types of electrodes were inserted in the electrospinning chamber to alter the electric field and have better control over the shape of the 3D structure. The upscalability of this technology was investigated by using a standard electrospinner and a nozzle-free electrospinning setup. It was possible to manufacture 3D structures with these devices, highlighting the versatility of this technology. 3D electrospinning opens the pathway for the facile fabrication of macroscopic 3D structure with microfibrous features on a commercial scale.

Three-dimensional (3D) printing is revolutionizing the manufacturing process of the 21st century. However, the commonly used 3D printing technology has its limitations in their resolution, as well as in their fabrication speed. This chapter introduces the 3D/4D electrospinning technique, which offers solutions to these limitations. With the 3D/4D electrospinning technology, it is possible to assemble macroscopic 3D shapes with internal polymer/composite micro- and nanofibers. Within 10 min, a structure height of 3–4 cm can be achieved and still self-standing after 1 year of storage at ambient conditions. The chapter starts by explanation background of electrospinning and methods to fabricate 3D polymer micro- and nanostructures. Then, it presents its principles and the details of the 3D/4D electrospinning technology, apparatus, process, characterization, and parameters. The potential applications and the future of 3D and 4D electrospinning are explained at the end, particularly for biomedical and energy applications.

Constructing nanotubular morphologies and heterojunctions are two effective strategies to enhance the charge separation and transport of alpha-Fe2O3 for improved photocatalytic performance, while the fabrication of porous aFe(2)O(3) nanotubes with precisely tailored wall thickness, pore structure, crystallinity, and junctions still remains a big challenge. Herein, two novel molecular layer deposition (MLD) procedures are designed to prepare porous Fe2O3 nanotubes with tunable pore structure and phase junction. The organic fractions of the obtained Fe-hybrid MLD films not only act as soft templates to generate nanopores in nanotube walls but also play a key role in the formation of phase-junction. The porous structure and phase-junction significantly improve the mass diffusion and charge separation efficiency of Fe2O3 nanotubes, leading to a drastically increased photocatalytic activity for photo-Fenton reaction. Especially, the porous alpha-gamma Fe2O3 nanotubes produced by two-step AB MLD from iron tert-butoxide and ethylene glycol exhibit the highest photocatalytic activity, which is more than a 6.5-fold and 20-fold improvement compared with the nonporous pure alpha-Fe2O3 nanotubes and commercial alpha-Fe2O3 nano-particles, respectively. The MLD method provides a new bottom-up approach to develop efficient Fe2O3 based heterostructure porous photocatalysts for waste-water cleaning and water splitting.

The combination of electrospinning with extrusion based 3D printing technology opens new pathways for micro- and nanofabrication, which can be applied in a wide range of applications. This simple and inexpensive method has been proven to fabricate 3D fibrous polystyrene structures with controlled morphology and micro- to nano-scale fibers diameter. The controllable movement of the nozzle allows precise positioning of the deposition area of the fibers during electrospinning. A programmed circular nozzle pattern results in the formation of controllable 3D polystyrene designed shapes with fiber diameters down to 550 nm. The assembly of the fibrous structures starts instantaneously, and a 4 cm tall and 6 cm wide sample can be produced within a 10 minutes electrospinning process. The product exhibits high stability at ambient conditions. The shape, size, and thickness of fibrous polystyrene structures can be easily controlled by tuning the process parameters. It is assumed that the build-up of 3D fibrous polystyrene structures strongly depends on charge induction and polarization of the electrospun fibers.

Infrared nanospectroscopy enables novel possibilities for chemical and structural analysis of nanocomposites, biomaterials or optoelectronic devices. Here we introduce hyperspectral infrared nanoimaging based on Fourier transform infrared nanospectroscopy with a tunable bandwidth-limited laser continuum. We describe the technical implementations and present hyperspectral infrared near-field images of about 5,000 pixel, each one covering the spectral range from 1,000 to 1,900 cm-1. To verify the technique and to demonstrate its application potential, we imaged a three-component polymer blend and a melanin granule in a human hair cross-section, and demonstrate that multivariate data analysis can be applied for extracting spatially resolved chemical information. Particularly, we demonstrate that distribution and chemical interaction between the polymer components can be mapped with a spatial resolution of about 30 nm. We foresee wide application potential of hyperspectral infrared nanoimaging for valuable chemical materials characterization and quality control in various fields ranging from materials sciences to biomedicine.

We present a simple synthesis of iron oxide nanotubes, grown under very mild conditions from a solution containing Fe(II) and Fe(III), on rod-shaped tobacco mosaic virus templates. Their well-defined shape and surface chemistry suggest that these robust bionanoparticles are a versatile platform for synthesis of small, thin mineral tubes, which was achieved efficiently. Various characterization tools were used to explore the iron oxide in detail: Electron microscopy (SEM, TEM), magnetometry (SQUID-VSM), diffraction (XRD, TEM-SAED), electron spectroscopies (EELS, EDX, XPS), and X-ray absorption (XANES with EXAFS analysis). They allowed determination of the structure, crystallinity, magnetic properties, and composition of the tubes. The protein surface of the viral templates was crucial to nucleate iron oxide, exhibiting analogies to biomineralization in natural compartments such as ferritin cages.

Electrospinning is known mainly for polymers. We show that this simple technique allows to shape molecules that are useful for organic photovoltaic cells into wires, a morphology that is otherwise not generally obtained. A special advantage of our method is the simple mixing approach that allows to test blends of promising compounds, without the need for chemical pretreatment, modification or immobilization. Our materials are TPP‐NH2 (monoamino‐tetraphenylporphyrine) and FF‐TPP (diphenylalanine‐TPP), both candidates for electron donors in solar cells. We found that a mixture of FF‐TPP with FF (diphenylalanine) is especially advantageous for forming quasi infinitely long wires of 100 to 1000 nm diameter. We analyzed the wire morphology with optical, electron, and scanning force microscopy, and we used X‐ray diffraction and infrared spectroscopy to elucidate the internal structure. The wire is composed of intact molecules, but shows surprisingly low crystallinity, in stark contrast to the single components.

Mid-infrared spectroscopy is a widely used tool for material identification and secondary structure analysis in chemistry, biology and biochemistry. However, the diffraction limit prevents nanoscale protein studies. Here we introduce mapping of protein structure with 30 nm lateral resolution and sensitivity to individual protein complexes by Fourier transform infrared nanospectroscopy (nano-FTIR). We present local broadband spectra of one virus, ferritin complexes, purple membranes and insulin aggregates, which can be interpreted in terms of their α-helical and/or β-sheet structure. Applying nano-FTIR for studying insulin fibrils--a model system widely used in neurodegenerative disease research--we find clear evidence that 3-nm-thin amyloid-like fibrils contain a large amount of α-helical structure. This reveals the surprisingly high level of protein organization in the fibril's periphery, which might explain why fibrils associate. We envision a wide application potential of nano-FTIR, including cellular receptor in vitro mapping and analysis of proteins within quaternary structures.