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1. Emerging investigator series: 3D printed graphene-biopolymer aerogels for water contaminant removal: a proof of concept

   https://doi.org/10.1039/D0EN00953A  

   Masud, Arvid ; Zhou, Chi ; Aich, Nirupam ( January 2021 , Environmental Science: Nano)

   null (Ed.)

   Graphene-based 3D macroscopic aerogels with their hierarchical porous structures and mechanical strength have been widely explored for removing contaminants from water. However, their large-scale manufacturing and application in various water treatment processes are limited by their scalability. In this study, we report a proof-of-concept direct ink writing (DIW) 3D printing technique and subsequent freeze-drying to prepare graphene-biopolymer aerogels for water treatment. To provide appropriate rheology for DIW printability, two bio-inspired polymers, polydopamine (PDA) and bovine serum albumin (BSA), were added to the graphene-based ink. The biopolymers also contributed to the contaminant removal capacity of the resultant graphene-polydopamine-bovine serum albumin (G-PDA-BSA) aerogel. The physicochemical properties of the aerogel were thoroughly characterized from the nano- to macroscale. The 3D printed aerogel exhibited excellent water contaminant removal performance for heavy metals (Cr( vi ), Pb( ii )), organic dyes (cationic methylene blue and anionic Evans blue), and organic solvents ( n -hexane, n -heptane, and toluene) in batch adsorption studies. The electrostatic interaction dominated the removal of heavy metals and dyes while the hydrophobic interaction dominated the removal of organic solvents from water. Moreover, the aerogel showed superb regeneration and reuse potential. The aerogel removed 100% organic solvents over 10 cycles of regeneration and reuse; additionally, the removal efficiencies for methylene blue decreased by 2–20% after the third cycle. The fit-for-design 3D printed aerogel was also effectively used as a bottle-cap flow-through filter for dye removal. The potential and vision of the 3D printing approach for graphene-based water treatment presented here can be extended to other functional nanomaterials, can enable shape-specific applications of fit-for-purpose adsorbents/reactors and point-of-use filters, and can materialize the large-scale manufacturing of nano-enabled water treatment devices and technologies. 

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2. Additive Manufacturing of Poly(phenylene Sulfide) Aerogels via Simultaneous Material Extrusion and Thermally Induced Phase Separation

   https://doi.org/10.1002/adma.202307881  

   Godshall, Garrett F. ; Rau, Daniel A. ; Williams, Christopher B. ; Moore, Robert B. ( December 2023 , Advanced Materials)

   Additive manufacturing (AM) of aerogels increases the achievable geometric complexity, and affords fabrication of hierarchically porous structures. In this work, a custom heated material extrusion (MEX) device prints aerogels of poly(phenylene sulfide) (PPS), an engineering thermoplastic, via in situ thermally induced phase separation (TIPS). First, pre‐prepared solid gel inks are dissolved at high temperatures in the heated extruder barrel to form a homogeneous polymer solution. Solutions are then extruded onto a room‐temperature substrate, where printed roads maintain their bead shape and rapidly solidify via TIPS, thus enabling layer‐wise MEX AM. Printed gels are converted to aerogels via postprocessing solvent exchange and freeze‐drying. This work explores the effect of ink composition on printed aerogel morphology and thermomechanical properties. Scanning electron microscopy micrographs reveal complex hierarchical microstructures that are compositionally dependent. Printed aerogels demonstrate tailorable porosities (50.0–74.8%) and densities (0.345–0.684 g cm⁻³), which align well with cast aerogel analogs. Differential scanning calorimetry thermograms indicate printed aerogels are highly crystalline (≈43%), suggesting that printing does not inhibit the solidification process occurring during TIPS (polymer crystallization). Uniaxial compression testing reveals that compositionally dependent microstructure governs aerogel mechanical behavior, with compressive moduli ranging from 33.0 to 106.5 MPa.

    

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3. Biomimetic 3D Printing of Hierarchical and Interconnected Porous Hydroxyapatite Structures with High Mechanical Strength for Bone Cell Culture

   https://doi.org/10.1002/adem.201800678  

   Song, Xiaolei ; Tetik, Halil ; Jirakittsonthon, Thitikan ; Parandoush, Pedram ; Yang, Guang ; Lee, Donghee ; Ryu, Sangjin ; Lei, Shuting ; Weiss, Mark L. ; Lin, Dong ( December 2018 , Advanced Engineering Materials)

   Human bone demonstrates superior mechanical properties due to its sophisticated hierarchical architecture spanning from the nano/microscopic level to the macroscopic. Bone grafts are in high demand due to the rising number of surgeries because of increasing incidence of orthopedic disorders, non‐union fractures, and injuries in the geriatric population. The bone scaffolds need to provide porous matrix with interconnected porosity for tissue growth as well as sufficient strength to withstand physiological loads, and be compatible with physiological remodeling by osteoclasts/osteoblasts. The‐state‐of‐art additive manufacturing (AM) technologies for bone tissue engineering enable the manipulation of gross geometries, for example, they rely on the gaps between printed materials to create interconnected pores in 3D scaffolds. Herein, the authors firstly print hierarchical and porous hydroxyapatite (HAP) structures with interconnected pores to mimic human bones from microscopic (below 10 µm) to macroscopic (submillimeter to millimeter level) by combining freeze casting and extrusion‐based 3D printing. The compression test of 3D printed scaffold demonstrates superior compressive stress (22 MPa) and strain (4.4%). The human mesenchymal stromal cells (MSCs) tests demonstrate the biocompatibility of printed scaffold.

    

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4. 3D Printed MXene Aerogels with Truly 3D Macrostructure and Highly Engineered Microstructure for Enhanced Electrical and Electrochemical Performance

   https://doi.org/10.1002/adma.202104980  

   Tetik, Halil ; Orangi, Jafar ; Yang, Guang ; Zhao, Keren ; Mujib, Shakir Bin ; Singh, Gurpreet ; Beidaghi, Majid ; Lin, Dong ( November 2021 , Advanced Materials)

   Assembling 2D materials such as MXenes into functional 3D aerogels using 3D printing technologies gains attention due to simplicity of fabrication, customized geometry and physical properties, and improved performance. Also, the establishment of straightforward electrode fabrication methods with the aim to hinder the restack and/or aggregation of electrode materials, which limits the performance of the electrode, is of great significant. In this study, unidirectional freeze casting and inkjet‐based 3D printing are combined to fabricate macroscopic porous aerogels with vertically aligned Ti₃C₂T_xsheets. The fabrication method is developed to easily control the aerogel microstructure and alignment of the MXene sheets. The aerogels show excellent electromechanical performance so that they can withstand almost 50% compression before recovering to the original shape and maintain their electrical conductivities during continuous compression cycles. To enhance the electrochemical performance, an inkjet‐printed MXene current collector layer is added with horizontally aligned MXene sheets. This combines the superior electrical conductivity of the current collector layer with the improved ionic diffusion provided by the porous electrode. The cells fabricated with horizontal MXene sheets alignment as current collector with subsequent vertical MXene sheets alignment layers show the best electrochemical performance with thickness‐independent capacitive behavior.

    

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5. Fluid Flow Analysis for Suitable 3D Bio-Printed Scaffold Architectures to Incubate in a Perfusion Bioreactor: A Simulation Approach

   https://doi.org/10.1115/msec2023-104324  

   Clark, Scott ; Quigley, Connor ; Mankowsky, Jack ; Habib, MD Ahasan ( June 2023 , Proceedings of the ASME 2023 18th International Manufacturing Science and Engineering Conference (MSEC2023))

   Due to the three-dimensional nature of the 3D bio-printed scaffolds, typical stagnant cell culturing methods don’t ensure entering medium inside areas or passing through the scaffolds. The bioreactor has frequently provided the required growth medium to encapsulated- and seeded-cells in 3D bio-printed scaffolds. To address this issue, we developed a customized perfusion bioreactor to supply the growth medium dynamically to the cells encapsulated or seeded in the scaffolds. The dynamic supply of fresh growth medium may help improve cell viability and proliferation. Because of its uniform nutrition distribution and flow-induced shear stress within the tissue-engineering scaffold, perfusion bioreactors have been used in a variety of tissue engineering applications. Including a modified setup of our designed bioreactor may improve the in vivo stimuli and conditions, eventually enhancing the overall performance of tissue regeneration. In this paper, we explored the response of fluid flow to certain types of scaffold pore geometries and porosities. We used a simulation technique to determine fluid flow turbulence through various pore geometries such as uniform triangular, square, diamond, circular, and honeycomb. We used variable pore sizes of the scaffold maintaining constant porosity to analyze the fluid flow. Based on the results, optimum designs for scaffolds were determined.

    

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