@article{fallah_asif_gokcer_koc_2023, title={4D printing of continuous fiber-reinforced electroactive smart composites by coaxial additive manufacturing}, volume={316}, ISSN={["1879-1085"]}, DOI={10.1016/j.compstruct.2023.117034}, abstractNote={In this study, a coaxial additive manufacturing process was developed for four-dimensional (4D) printing with continuous carbon fiber-reinforced shape memory polymers (SMPs). These materials have potential applications in the aerospace, automotive, and biomedical industries due to their high strength-to-weight ratio and shape memory properties. The mechanical and thermal properties of the SMPs were evaluated and the effects of printing parameters on printability and carbon fiber volume fraction were analyzed to determine optimal printing conditions. It was found that even a small amount of carbon fiber significantly improved the mechanical properties of the 4D printed samples. The shape memory properties of the printed samples were also examined, and it was found that the structure was able to recover the original shape quickly at low-temperature programming, making it suitable for load-bearing structures. At high-temperature programming, the structure retained the programmed shape well, but recovery of the original shape was slower and incomplete. The use of continuous carbon fiber reinforced SMPs also allows for Joule heating to be used for shape recovery, with the applied voltage able to control the shape recovery process. A high level of deformation recovery (95%) was also achieved in highly deformed structures.}, journal={COMPOSITE STRUCTURES}, author={Fallah, Ali and Asif, Suleman and Gokcer, Gizem and Koc, Bahattin}, year={2023}, month={Jul} }
 @article{chansoria_asif_gupta_piedrahita_shirwaiker_2022, title={Multiscale Anisotropic Tissue Biofabrication via Bulk Acoustic Patterning of Cells and Functional Additives in Hybrid Bioinks}, volume={1}, ISSN={["2192-2659"]}, DOI={10.1002/adhm.202102351}, abstractNote={AbstractRecapitulation of the microstructural organization of cellular and extracellular components found in natural tissues is an important but challenging feat for tissue engineering, which demands innovation across both process and material fronts. In this work, a highly versatile ultrasound‐assisted biofabrication (UAB) approach is demonstrated that utilizes radiation forces generated by superimposing ultrasonic bulk acoustic waves to rapidly organize arrays of cells and other biomaterial additives within single and multilayered hydrogel constructs. UAB is used in conjunction with a novel hybrid bioink system, comprising of cartilage‐forming cells (human adipose‐derived stem cells or chondrocytes) and additives to promote cell adhesion (collagen microaggregates or polycaprolactone microfibers) encapsulated within gelatin methacryloyl (GelMA) hydrogels, to fabricate cartilaginous tissue constructs featuring bulk anisotropy. The hybrid matrices fabricated under the appropriate synergistic thermo‐reversible and photocrosslinking conditions demonstrate enhanced mechanical stiffness, stretchability, strength, construct shape fidelity and aligned encapsulated cell morphology and collagen II secretion in long‐term culture. Hybridization of UAB is also shown with extrusion and stereolithography printing to fabricate constructs featuring 3D perfusable channels for vasculature combined with a crisscross or circumferential organization of cells and adhesive bioadditives, which is relevant for further translation of UAB toward complex physiological‐scale biomimetic tissue fabrication.}, journal={ADVANCED HEALTHCARE MATERIALS}, author={Chansoria, Parth and Asif, Suleman and Gupta, Nithin and Piedrahita, Jorge and Shirwaiker, Rohan A.}, year={2022}, month={Jan} }
 @article{chansoria_asif_polkoff_chung_piedrahita_shirwaiker_2021, title={Characterizing the Effects of Synergistic Thermal and Photo-Cross-Linking during Biofabrication on the Structural and Functional Properties of Gelatin Methacryloyl (GeIMA) Hydrogels}, volume={7}, ISSN={["2373-9878"]}, DOI={10.1021/acsbiomaterials.1c00635}, abstractNote={Gelatin methacryloyl (GelMA) hydrogels have emerged as promising and versatile biomaterial matrices with applications spanning drug delivery, disease modeling, and tissue engineering and regenerative medicine. GelMA exhibits reversible thermal cross-linking at temperatures below 37 °C due to the entanglement of constitutive polymeric chains, and subsequent ultraviolet (UV) photo-cross-linking can covalently bind neighboring chains to create irreversibly cross-linked hydrogels. However, how these cross-linking modalities interact and can be modulated during biofabrication to control the structural and functional characteristics of this versatile biomaterial is not well explored yet. Accordingly, this work characterizes the effects of synergistic thermal and photo-cross-linking as a function of GelMA solution temperature and UV photo-cross-linking duration during biofabrication on the hydrogels' stiffness, microstructure, proteolytic degradation, and responses of NIH 3T3 and human adipose-derived stem cells (hASC). Smaller pore size, lower degradation rate, and increased stiffness are reported in hydrogels processed at lower temperature or prolonged UV exposure. In hydrogels with low stiffness, the cells were found to shear the matrix and cluster into microspheroids, while poor cell attachment was noted in high stiffness hydrogels. In hydrogels with moderate stiffness, ones processed at lower temperature demonstrated better shape fidelity and cell proliferation over time. Analysis of gene expression of hASC encapsulated within the hydrogels showed that, while the GelMA matrix assisted in maintenance of stem cell phenotype (CD44), a higher matrix stiffness resulted in higher pro-inflammatory marker (ICAM1) and markers for cell-matrix interaction (ITGA1 and ITGA10). Analysis of constructs with ultrasonically patterned hASC showed that hydrogels processed at higher temperature possessed lower structural fidelity but resulted in more cell elongation and greater anisotropy over time. These findings demonstrate the significant impact of GelMA material formulation and processing conditions on the structural and functional properties of the hydrogels. The understanding of these material-process-structure-function interactions is critical toward optimizing the functional properties of GelMA hydrogels for different targeted applications.}, number={11}, journal={ACS BIOMATERIALS SCIENCE & ENGINEERING}, author={Chansoria, Parth and Asif, Suleman and Polkoff, Kathryn and Chung, Jaewook and Piedrahita, Jorge A. and Shirwaiker, Rohan A.}, year={2021}, month={Nov}, pages={5175–5188} }
 @article{asif_chansoria_shirwaiker_2020, title={Ultrasound-assisted vat photopolymerization 3D printing of preferentially organized carbon fiber reinforced polymer composites}, volume={56}, ISSN={["2212-4616"]}, DOI={10.1016/j.jmapro.2020.04.029}, abstractNote={In this study, we present a new vat photopolymerization 3D printing process that uses acoustic radiation forces from ultrasonic standing waves to organize carbon short fibers within a photocurable resin. A chamber was developed to generate the standing bulk acoustic wave in the resin to align the carbon fibers along the nodes of the standing wave. The resin was then selectively cured to create constructs in the shape of a dog bone specimen by exposing to UV. The effect of fiber concentration (0.5 %, 1 %, 2 %, and 4 % w/v) and direction of alignment (parallel, perpendicular) on tensile strength of the carbon fiber reinforced polymer composites was determined. The constructs with 1 % w/v showed the highest gain in tensile strength due to the fiber alignment. For two-layered constructs with 1 % fiber concentration, 0°–0° constructs (fibers aligned along the uniaxial testing direction) demonstrated significantly higher tensile strength followed by 0°–90°constructs compared to constructs with randomly distributed fibers and without fibers.}, journal={JOURNAL OF MANUFACTURING PROCESSES}, author={Asif, Suleman and Chansoria, Parth and Shirwaiker, Rohan}, year={2020}, month={Aug}, pages={1340–1343} }