Multi-material Printing Research Articles

(Battery Division Postdoctoral Associate Research Award Sponsored by MTI Corporation and the Jiang Family Foundation) 3D Printing of Batteries: Fiction or Reality?

Motivated by the request to build shape-conformable flexible, wearable and customizable batteries while maximizing the energy storage and electrochemical performances, additive manufacturing (AM) appears as a revolutionary discipline. Battery components such as electrodes, separator, electrolyte, current collectors and casing can be tailored with any shape, allowing the direct incorporation of batteries and all electronics within the final three-dimensional object. AM also paves the way toward the implementation of complex 3D electrode architectures that could enhance significantly the power battery performances. Transitioning from conventional 2D to complex 3D lithium-ion battery (LIB) architectures will increase the electrochemically active surface area, enhance the Li+ diffusion paths, thus leading to improved specific capacity and power performance [1]. Our recent modeling studies [2] involving the simulation of a classical Ragone plot illustrated that a gyroid 3D battery architecture has +158% performance at a high current density of 6C, in comparison to planar geometry.In this presentation, an overview of current trends in energy storage 3D printing will be discussed [3-11]. A summary of our recent works on lithium-ion battery 3D printing via Thermoplastic Material Extrusion / Fused Deposition Modeling will be presented [12-16]. The development of printable composite filaments (Graphite-, LiFePO4-, Li2TP-, PEO/LiTFSI-, SiO2-, Ag/Cu-based) corresponding to each part of a LIB (electrodes, electrolyte, separator, current collectors), and the importance of introducing a plasticizer (polyethylene glycol dimethyl ether average Mn 500 for polylactic acid) as an additive to enhance the printability will be addressed. Printing of the complete LIB in a single step using multi-material printing options, and the implementation of a solvent-free protocol [14] will also be discussed. Second part of this presentation will be dedicated to AM of batteries by means of Vat Photopolymerization (VPP) processes, including stereolithography, digital light processing and two-photon polymerization (offering a greater resolution down to 0.1μm), to print high resolution battery components [10]. Composite resins formulation approaches based on the introduction of solid battery particles or precursor salts will be introduced [17, 18]. Finally, an overview of our ongoing project dedicatedto AM of sodium-ion batteries from resources available on the Moon and Mars will be presented. Due to its relative abundance in the Lunar regolith, the development of a composite photocurable resin loaded with TiO2 negative electrode material and conductive additives, to feed a VPP printer, will be discussed [18].[1] Long et al., Three-dimensional battery architectures, Chemical Reviews 104(10) (2004) 4463-4492.[2] Maurel et al., Considering lithium-ion battery 3D-printing via thermoplastic material extrusion and polymer powder bed fusion, Additive Manufacturing (2020) 101651.[3] Maurel et al., Overview on Lithium-Ion Battery 3D-Printing By Means of Material Extrusion, ECS Transactions 98(13) (2020) 3-21.[4] Ragones et al., Towards smart free form-factor 3D printable batteries, Sustainable Energy & Fuels 2(7) (2018) 1542-1549.[5] Reyes et al., Three-Dimensional Printing of a Complete Lithium Ion Battery with Fused Filament Fabrication, ACS Applied Energy Materials 1(10) (2018) 5268-5279.[6] Yee et al., Hydrogel-Based Additive Manufacturing of Lithium Cobalt Oxide, Advanced Materials Technologies 6(2) (2021).[7] Saccone et al., Understanding and mitigating mechanical degradation in lithium–sulfur batteries: additive manufacturing of Li2S composites and nanomechanical particle compressions, Journal of Materials Research (2021).[8] Tagliaferri et al., Direct ink writing of energy materials, Materials Advances 2(2) (2021) 25.[9] Sun et al., 3D Printing of Interdigitated Li-Ion Microbattery Architectures, Advanced Materials 25(33) (2013) 4539-4543.[10] Maurel et al., Toward High Resolution 3D Printing of Shape-Conformable Batteries via Vat Photopolymerization: Review and Perspective, IEEE Access 9 (2021) 140654-140666.[11] Seol et al., All-Printed In-Plane Supercapacitors by Sequential Additive Manufacturing Process, Acs Applied Energy Materials 3(5) (2020) 4965-4973.[12] Maurel et al., Highly Loaded Graphite-Polylactic Acid Composite-Based Filaments for Lithium-Ion Battery Three-Dimensional Printing, Chemistry of Materials 30(21) (2018) 7484-7493.[13] Maurel et al., Three-Dimensional Printing of a LiFePO4/Graphite Battery Cell via Fused Deposition Modeling, Scientific Reports 9(1) (2019) 18031.[14] Maurel et al., Environmentally Friendly Lithium-Terephthalate/Polylactic Acid Composite Filament Formulation for Lithium-Ion Battery 3D-Printing via Fused Deposition Modeling, ECS Journal of Solid State Science and Technology 10(3) (2021) 037004.[15] Maurel et al., Poly(Ethylene Oxide)-LiTFSI Solid Polymer Electrolyte Filaments for Fused Deposition Modeling Three-Dimensional Printing, Journal of the Electrochemical Society 167(7) (2020).[16] Maurel et al., Ag-Coated Cu/Polylactic Acid Composite Filament for Lithium and Sodium-Ion Battery Current Collector Three-Dimensional Printing via Thermoplastic Material Extrusion, Frontiers in Energy Research 9(70) (2021).[17] Martinez et al., Additive Manufacturing of LiNi1/3Mn1/3Co1/3O2 battery electrode material via vat photopolymerization precursor approach, (submitted).[18] Maurel et al., Vat Photopolymerization Additive Manufacturing of Sodium-Ion Battery TiO2 Negative Electrodes from Lunar In-Situ Resources, (submitted).

Sandwich structure printing of Ti-Ni-Ti by directed energy deposition

ABSTRACT In the current work, sandwich structure (Ti-6Al-4V)-Ni-(Ti-6Al-4V) is printed by Laser Engineered Net Shaping (LENS). This sandwich structure allows the general repair of broken parts with dissimilar materials. The chief objective of this research is to propose a new method to produce a sandwich structure comprising Ti-6Al-4V and Nickel by DED, which allows the investigation of the Ti-6Al-4V/Nickel and Nickel/Ti-6Al-4V interfaces. The results shed light on the production process and makes a proper roadmap for multi-material printing. The contributions of this paper are the detailed defect characterization of (Ti-6Al-4V)-Ni-(Ti-6Al-4V) sandwich structures, considering the rheological phenomena in the meltpool and thermophysical properties of the materials. This research also identifies how the interface quality and the overall bonding quality of the sandwich structures can be improved, enabling the exploration of the limitations of production, and the knowledge of how to potentially produce a defect-free sandwich structure of Ti-Ni-Ti. Results showed that cracks, pores, partial melting, keyholes and residual particles are the main problems during a build. These results indicate that the LENS is a promising method to produce sandwich structures for various applications by selecting the appropriate process parameters in such a way as to minimize the rheological instability.

A computational design approach for multi-material 4D printing based on interlocking blocks assembly

4D printing is considered as a disruptive manufacturing technology for creating innovative devices able to evolve in their usage environment. By coupling additive manufacturing (AM) processes and active/passive materials under the effect of an energy stimulation, objects can change properties, shapes, or even functionalities. To achieve a desired shape-change, recent advances in computational design around digital materials require tackling multi-material 4D printing. However, the deposition of active and passive materials in a single run remains difficult due to the different AM techniques required. To overcome this limitation in the context of complex materials distributions, an original approach is to address multi-material 4D printing from the perspective of interlocking blocks assembly. Therefore, the objective of the paper is to propose a computational design approach that converts a multi-material 4D object with a computed digital materials distribution into suitable interlocking blocks. The latter can be printed separately using single material AM and then assembled to achieve the targeted shape change. An implementation of the approach via a dedicated plugin within a computer-aided design environment is presented. A case study is introduced to illustrate the relevance and the applicability of the proposed approach.

Modular speaker design enabled by multi-material additive manufacturing

One of the most promising features of additive manufacturing is ability to reduce part count and assembly by printing complex shapes. This feature is further highlighted by utilizing multi-material printing in which stiff and compliant materials can be deposited by the same system. Air-acoustic speakers are traditionally comprised of several assembled components with different material properties including a stiff enclosure, stiff diaphragm, and compliant suspension. In this presentation, we will describe a modular acoustic speaker design. The design consists of fully printed structural components (which are threaded together, and assembled with a voice coil and magnet). The basic design as well as printing process will be described and acoustic measurements reported. A range of printed designs, which can be interchanged among each-other will be presented, and future design ideas which take advantage of the printing process explored.

Advanced software development of 2D and 3D model visualization for TwinPrint, a dual-arm 3D bioprinting system for multi-material printing

This research highlights the development of a two-dimensional (2D) and three-dimensional (3D) preview software for additive manufacturing (AM). The presented software can produce a virtual representation of an actuator’s path movements by reading and parsing the orders of the desired geometric code (G-code) file. It then simulates the coded sections into separate 2D layers and colored 3D objects in a graphical model. This allows users to validate the shapes before the 3D printing process. G-code is an operation language which is based on command lines of code written in an alphanumeric format. Each line of these commands controls one machining operation; this instructs the machine’s motion to move in an arc, a circle, or a straight line to perform a specific shape after compiling all code lines. AM technology is widely used in most manufacturing fields (e.g., medical, chemical, and research laboratories) as a prototyping technology due to its ability to produce rapid prototyping models. 3D printing creates physical 3D models by extruding material layer by layer as 2D layers. At present, the most critical challenges in AM technology are drastically reducing prototyping materials’ consumption and time spent. To address these challenges, the proposed software allows for visualization of G-code files and predicting the overall layers’ shapes, allowing both structure prediction and subsequent printing error reduction.

Vision-Based Quality Assurance of Composites Printed by Extrusion-Based 3D-Printers

Additive manufacturing (AM) has been emerging as a promising production approach due to its expanded design freedoms and cost-effective batch size. Yet, its commercial acceptance is hindered by technical challenges in terms of quality assurance and defects of printed parts. Conventionally, this results in failed parts, waste of time, labor, and material. Though there have been successful attempts for process monitoring and quality assurance for single-material additive manufacturing processes, limited work has been reported for multi-material printing applications. This paper proposes a vision-based method for characterizing the material deposition accuracy of multi-material printing. More specifically, layer-wise images of a printed part are acquired, segmented, and compared with its equivalent digital reference, and position accuracy is measured by pixel differences, which provides a feasible solution for evaluating the overall performance of the multi-material AM process. An exploratory image acquiring setup using an offline camera is presented to experimentally validate the feasibility of the proposed workflow. The study concludes that detecting material deposition errors for two contrasting materials offers promising feasibility by using image processing methods and using the histogram of the image can quantify the degree of inaccuracy. This research provides a preliminary base for further research in the direction of integrating image acquisition systems with the printer, automating the image processing stage and extending the image histogram reading techniques for higher precision.

A new boundary interlock geometry design pattern to strengthen FDM part multi-material interface

Multi-material Fused Deposition Modeling (FDM) enables the realization of designs in complex geometries with multiple materials. However, achieving an adequate level of interfacial bonding strength between different materials remains a significant challenge. Other than addressing this challenge through material bonding at molecular scale or optimizing the printing parameters, new design methodologies also pose good potential. This work studied the mechanical properties of multi-material printed objects, with a particular focus on the interface zone built between the various materials at their geometrical borders. Four types of test samples were designed, printed, and tested: (A) single-material test samples uni-body (without boundary interface); (B) single-material test samples with planar boundary interface; (C) bi-material test samples with a planar boundary interface; and (D) bi-material test samples with new boundary interlock geometry design interface. The comparison of the mechanical performance between Type-A, -B, and -C test samples demonstrated the influence of the presence of a geometrical boundary interface between the same material and different materials. The comparison between Type-C and -D demonstrated the impact of introducing boundary interlock geometry. This study showed that with the new boundary interlock geometry design, the mechanical strength (tensile strength) of multi-material prints can be greatly improved. Furthermore, a Design of Experiment is conducted to identify the interlock geometry design parameters optimized for tensile strength. This work proves the significance of boundary interlock geometry design in multi-material printing and provides a methodology to explore new boundary interlock geometry design patterns to strengthen the FDM part multi-material interface.

Magnetically assisted drop-on-demand 3D printing of microstructured multimaterial composites

Microstructured composites with hierarchically arranged fillers fabricated by three-dimensional (3D) printing show enhanced properties along the fillers’ alignment direction. However, it is still challenging to achieve good control of the filler arrangement and high filler concentration simultaneously, which limits the printed material’s properties. In this study, we develop a magnetically assisted drop-on-demand 3D printing technique (MDOD) to print aligned microplatelet reinforced composites. By performing drop-on-demand printing using aqueous slurry inks while applying an external magnetic field, MDOD can print composites with microplatelet fillers aligned at set angles with high filler concentrations up to 50 vol%. Moreover, MDOD allows multimaterial printing with voxelated control. We showcase the capabilities of MDOD by printing multimaterial piezoresistive sensors with tunable performances based on the local microstructure and composition. MDOD thus creates a large design space to enhance the mechanical and functional properties of 3D printed electronic or sensing devices using a wide range of materials.

Inkjet four-dimensional printing of shape memory polymers: a review

PurposeThis paper aims to provide a review of four-dimensional (4D) printing of shape memory polymers using inkjet printing technology. 4D printing refers to the three-dimensional (3D) printing of smart materials capable of shape change or function modification with respect to time when activated by external stimuli. Inkjet printing has gained popularity because of the technical advantages such as non-contact deposition, multi-material printing, high resolution, high speed of printing and minimal post processing. This review will serve as a platform for understanding the inkjet 4D printing process and the shape memory capability of the polymer structures printed using inkjet printing.Design/methodology/approachThe approach used in this review was to search for and review research works related to inkjet 4D printing of shape memory polymers. The search period was limited for the duration 2013 to 2021 as the 4D printing technology came into light later in 2013. With the review of inkjet 4D printing of shape memory polymers, the shape memory capability of the inkjet-printed structures were also studied.FindingsWith the available research documents, it was found that the inkjet 4D printing technology gained momentum from 2016, three years after the introduction of the 4D printing technology. The key findings of this review show that inkjet 4D printing of shape memory polymers were primarily performed using commercial inkjet printers and polymer inks linked to the printers. Even though the inkjet printing technology is matured enough to print multiple materials, development of shape memory polymer inks for inkjet printability remains complex. To realize the full potential of inkjet 4D printing, novel polymer inks specific for inkjet printing needs development.Research limitations/implicationsThe major limitation to this review was the availability of research papers for review. Even though inkjet printing technology has grown to popularity in the graphics printing and publishing industry since its inception in the 19th century, the technology still needs to evolve in the printing of 3D structures due to the limitations in synthesizing inks that are inkjet printable. However, this research will serve as a platform for understating the current status of inkjet 4D printing and the limitations of the technology.Originality/valueThis review focuses only on the inkjet 4D printing of shape memory polymers among the generally summarized 4D printing review papers available. Currently, 4D printing of shape memory polymers is carried out using only the commercially available polymer printers. Also, researchers do not have the flexibility of modifying the polymer inks linked to the printers. This review can spur more research into the development of novel polymer inks specific for inkjet printing.

Rapid and Multimaterial 4D Printing of Shape-Morphing Micromachines for Narrow Micronetworks Traversing.

Micromachines with high environmental adaptability have the potential to deliver targeted drugs in complex biological networks, such as digestive, neural, and vascular networks. However, the low processing efficiency and single processing material of current 4D printing methods often limit the development and application of shape-morphing micromachines (SMMs). Here, two 4D printing strategies are proposed to fabricate SMMs with pH-responsive hydrogels for complex micro-networks traversing. On the one hand, the 3Dvortex light single exposure technique can rapidly fabricate a tubular SMM with controllable size and geometry within 0.1 s. On the other hand, the asymmetric multimaterial direct laser writing (DLW)method is used to fabricate SMMs with designable 3D structures composed of hydrogel and platinum nanoparticles (Pt NPs). Based on the presence of ferroferric oxide (Fe3 O4 ) and Pt NPs in the SMMs, efficient magnetic, bubble, and hybrid propulsion modes are achieved. Finally, it is demonstrated that the spatial shape conversion capabilities of these SMMs can be used for narrow micronetworks traversing, which will find potential applications in targeted cargo delivery in microcapillaries.

Recent Advances in 3D Printed Sensors: Materials, Design, and Manufacturing

AbstractSensors are of great importance in different aspects of research and industry. Future sensors will require high‐efficient and low‐cost manufacturing, as well as high‐performance functionality in areas, such as mechanical sensing, biomedical, and optical applications. Recent advances in 3D printing open a new paradigm for sensors fabrication as a precision, customizable, and seamless process. In this article, the state‐of‐the‐art 3D printing methods in sensors manufacturing is reviewed and the performance of the 3D printed sensing materials and devices is summarized. Special attention is paid to emerging multimaterial printing and 4D printing technologies, which will benefit the fabrication of a new generation of structures with multifunctionalities. The content on 3D printed sensors covers piezoelectric sensors, medical, and optical sensing devices. The performance of 3D printed sensors in comparison with the sensors made by traditional manufacturing is also covered. Finally, section 4 provides the viewpoints on the future development of 3D printed sensors.

Multi-material printing of PVDF composites: A customized solution for maintenance of heritage structures

In the past three decades, 3D printing technologies have emerged as a convenient tool for the repair and maintenance of heritage structures. But hitherto little has been reported on multi-material 3D printed composites with 4D properties for the repair and maintenance of heritage structures. The present study reports the investigations on multi-material 3D printing of conducting and non-conducting polyvinylidene fluoride (PVDF) composite layers with self-actuating and self-healing properties to repair non-structural cracks in heritage buildings. The non-conducting (PVDF-CaCO3) and conducting (PVDF-graphene-Mn doped ZnO) composites were 3D printed and tested for electrostriction-based strain measurement for 4D analysis. The thermo-mechanical properties of the composite solution were obtained from dynamic mechanical analysis (DMA). The electrical, bonding, and morphological properties were investigated by current-voltage (I-V), x-ray diffraction (XRD), Fourier transformed infrared (FTIR), and scanning electron microscopy (SEM)-energy dispersive spectroscopy (EDS) analysis. Results of the self-elongation and contraction by electrostriction in PVDF composite demonstrate the feasibility of 3D printing technology as a novel tool to fabricate cost-effective smart solutions for the repair and maintenance of heritage structures.

Three-dimensional printing of photonic colloidal glasses into objects with isotropic structural color

Structural color is frequently exploited by living organisms for biological functions and has also been translated into synthetic materials as a more durable and less hazardous alternative to conventional pigments. Additive manufacturing approaches were recently exploited for the fabrication of exquisite photonic objects, but the angle-dependence observed limits a broader application of structural color in synthetic systems. Here, we propose a manufacturing platform for the 3D printing of complex-shaped objects that display isotropic structural color generated from photonic colloidal glasses. Structurally colored objects are printed from aqueous colloidal inks containing monodisperse silica particles, carbon black, and a gel-forming copolymer. Rheology and Small-Angle-X-Ray-Scattering measurements are performed to identify the processing conditions leading to printed objects with tunable structural colors. Multimaterial printing is eventually used to create complex-shaped objects with multiple structural colors using silica and carbon as abundant and sustainable building blocks.

Design and Analysis of a 5-Degree of Freedom (DOF) Hybrid Three-Nozzle 3D Printer for Wood Fiber Gel Material

Wood is an organic renewable natural resource. Cellulose, hemicellulose and lignin in wood are used in tissue engineering, biomedicine and other fields because of their good properties. This paper reported that the possibility of wood fiber gel material molding and the preparing of gel material were researched based on the wood fiber gel material as a 3D printing material. A five-degree of freedom hybrid three nozzle 3D printer was designed. The structural analysis, static analysis, modal analysis and transient dynamic analysis of 3D printers were researched, and the theoretical basis of the 3D printer was confirmed as correct and structurally sound. The results showed that the 5-DOF hybrid 3-nozzle 3D printer achieved the 3D printing of wood fiber gel material and that the printer is capable of multi-material printing and multi-degree-of-freedom printing.

Large-Scale Customized Production Scheduling of Multiagent-Based Medical 3D Printing.

Three-dimensional (3D) printing, also known as additive manufacturing, has unique advantages over traditional manufacturing technologies; thus, it has attracted widespread attention in the medical field. Especially in the context of the frequent occurrence of major public health events, where the medical industry's demand for large-scale and customized production is increasing, traditional 3D printing production scheduling methods take a long time to handle large-scale customized medical 3D printing (M-3DP) production and have weak intelligent collaboration ability in the face of job-to-device matching under multimaterial printing. Given the problem caused by M-3DP large-scale customized production scheduling, an intelligent collaborative scheduling multiagent-based method is proposed in this study. First, a multiagent-based optimization model is established. On this basis, an improved genetic algorithm embedded with the product mix strategy and the intelligent matching mechanism is designed to optimize the completion time and load balance between devices. Finally, the effectiveness of the proposed method is evaluated using numerical simulation. The simulation results indicated that compared with the simple genetic algorithm, particle swarm optimization, and snake optimizer, the improved genetic algorithm could better reduce the M-3DP mass customization production scheduling time, optimize the load balance between devices, and promote the “intelligent manufacturing” process of M-3DP mass customization.

Traction of 3D and 4D Printing in the Healthcare Industry: From Drug Delivery and Analysis to Regenerative Medicine.

Three-dimensional (3D) printing and 3D bioprinting are promising technologies for a broad range of healthcare applications from frontier regenerative medicine and tissue engineering therapies to pharmaceutical advancements yet must overcome the challenges of biocompatibility and resolution. Through comparison of traditional biofabrication methods with 3D (bio)printing, this review highlights the promise of 3D printing for the production of on-demand, personalized, and complex products that enhance the accessibility, effectiveness, and safety of drug therapies and delivery systems. In addition, this review describes the capacity of 3D bioprinting to fabricate patient-specific tissues and living cell systems (e.g., vascular networks, organs, muscles, and skeletal systems) as well as its applications in the delivery of cells and genes, microfluidics, and organ-on-chip constructs. This review summarizes how tailoring selected parameters (i.e., accurately selecting the appropriate printing method, materials, and printing parameters based on the desired application and behavior) can better facilitate the development of optimized 3D-printed products and how dynamic 4D-printed strategies (printing materials designed to change with time or stimulus) may be deployed to overcome many of the inherent limitations of conventional 3D-printed technologies. Comprehensive insights into a critical perspective of the future of 4D bioprinting, crucial requirements for 4D printing including the programmability of a material, multimaterial printing methods, and precise designs for meticulous transformations or even clinical applications are also given.

High-resolution multiceramic additive manufacturing based on digital light processing

High-precision ceramic components with the integration of multiple materials and structures have excellent prospects in the applications of microelectronics, biomedical engineering, aerospace, etc. However, previous additive manufacturing technologies are challenging to use or can only achieve multiceramic distribution among different layers. In this paper, we proposed a novel multiceramic additive manufacturing technology based on digital light processing. Considering the high viscosity characteristic of ceramic slurry, a multiceramic additive manufacturing system was set up with the cyclic process of “coating - exposure - cleaning - drying”. By designing a typical multimaterial pattern, the exposure sequence of different materials in a single layer was studied. In addition, we focused on the interface quality in the printed parts, including the XY and ZX(Y) interfaces. The generation mechanism of the “staggered layers effect” at the XY interface was revealed. To improve the ZX(Y) interface precision, the relationship between the designed width and the actual cure width is demonstrated, which is determined by the UV light scattering in ceramic slurry and the “edge loss effect” at the ZX(Y) interface. Based on this relationship, we presented an error compensation method for ensuring interface precision together with interface bonding. The results show that high-precision and defect-free multiceramic components can be obtained by this technology. This novel multimaterial printing system also shows great potential for photocurable slurries loaded with other particles, such as metal particles.

3D-printed electrochemical platform with multi-purpose carbon black sensing electrodes.

The 3D printing is described of a complete and portable system comprising a batch injection analysis (BIA) cell and an electrochemical platform with eight sensing electrodes. Both BIA and electrochemical cells were printed within 3.4 h using a multimaterial printer equipped with insulating, flexible, and conductive filaments at cost of ca. ~ U$ 1.2 per unit, and their integration was based on a threadable assembling without commercial component requirements. Printed electrodes were exposed to electrochemical/Fenton pre-treatments to improve the sensitivity. Scanning electron microscopy and electrochemical impedance spectroscopy measurements upon printed materials revealed high-fidelity 3D features (90 to 98%) and fast heterogeneous rate constants ((1.5 ± 0.1) × 10−3 cm s−1). Operational parameters of BIA cell were optimized using a redox probe composed of [Fe(CN)6]4−/3− under stirring and the best analytical performance was achieved using a dispensing rate of 9.0 µL s−1 and an injection volume of 2.0 µL. The proof of concept of the printed device for bioanalytical applications was evaluated using adrenaline (ADR) as target analyte and its redox activities were carefully evaluated through different voltammetric techniques upon multiple 3D-printed electrodes. The coupling of BIA system with amperometric detection ensured fast responses with well-defined peak width related to the oxidation of ADR applying a potential of 0.4 V vs Ag. The fully 3D-printed system provided suitable analytical performance in terms of repeatability and reproducibility (RSD ≤ 6%), linear concentration range (5 to 40 µmol L−1; R2 = 0.99), limit of detection (0.61 µmol L−1), and high analytical frequency (494 ± 13 h−1). Lastly, artificial urine samples were spiked with ADR solutions at three different concentration levels and the obtained recovery values ranged from 87 to 118%, thus demonstrating potentiality for biological fluid analysis. Based on the analytical performance, the complete device fully printed through additive manufacturing technology emerges as powerful, inexpensive, and portable tool for electroanalytical applications involving biologically relevant compounds.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s00604-022-05323-4.

FRESH 3D Bioprinted Collagen‐based Resistance Vessels and Multiscale Vascular Microfluidics

The pursuit of an ideal model system to study the pathophysiology of vascular disease has included the use of tissue engineered blood vessels (TEBV), vascularizing engineered volumetric tissue, silicone‐based “organ‐on‐a‐chip” platform, and tissue decellularization; yet we are still far from generating engineered vascular tissue that recapitulate native physiology. Despite advances such as 3D bioprinting that have led to new approaches for creating fluidic channels, it remains challenging to produce continuous networks with vessels ranging from large (>6 mm) to small (<1 mm) using native‐like extracellular matrix (ECM) that recapitulates the mechanical properties, geometric organization, and complexity of the cellular and extracellular microenvironment. An ideal engineering strategy would combine the controlled fluid flow achieved by organ‐on‐a‐chip platforms with the ECM structure, composition, and biomechanics of decellularized tissue. Here, using Freeform Reversible Embedding of Suspended Hydrogels (FRESH) 3D bioprinting, we spatially define ECM composition and vascular geometry to create collagen‐based microfluidics and an engineered resistance artery scaffold to study how ECM composition, mechanical properties, and fluid flow contribute to vascular disease. A 3D vascular microfluidic CAD model was designed with a hierarchically branching network containing a single inlet and outlet of 1 mm that branched down to 250 µm channels embedded within a collagen scaffold. This model was FRESH printed with 24 mg/mL collagen‐I and yielded a high‐fidelity scaffold with patent internal vasculature. 3D imaging and gauging analysis of the CAD model compared to the collagen scaffold revealed an average positive deviation of 9.9 µm and an average negative deviation of 56.3 µm. To interface with and perfuse the soft collagen microfluidic scaffold we 3D printed a custom bioreactor chamber for long‐term culture capable of >1‐week perfusion under physiological conditions. In addition to embedded vascular networks, FRESH bioprinting allows for direct fabrication of suspended vessels. We designed an ECM scaffold scaled to match a resistance vessel consisting of a collagen‐I frame and suspended vessel (inner diameter of 300 µm, outer diameter of 500 µm). The collagen frame provides overall scaffold stability and allows interfacing to the custom perfusion bioreactor. Using multimaterial FRESH printing, we varied the ECM composition by patterning fibronectin along the inner lumen and collagen‐I within the outer adventitial wall. Biomechanical evaluation using pressure and wire myography revealed a burst pressure >140 mmHg and an average peak tension of 600 mg, comparable to mouse mesenteric resistance arteries. Together, this work highlights the exciting potential for ECM‐based microfluidic scaffolds and vascular tissue engineering that will set the foundation for future work to replicate a healthy and hypertensive vessel microenvironment. In addition to vascular biology, the collagen‐based microfluidics are amenable to other organ systems, and can be utilized to study cell proliferation, metastasis, and ECM remodeling in a 3D environment.

Direct Ink Writing: A 3D Printing Technology for Diverse 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 asaguideline toward possible futuristic innovations.