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1. Novel 2D Dynamic Elasticity Maps for Inspection of Anisotropic Properties in Fused Deposition Modeling Objects

   https://doi.org/10.3390/polym12091966  

   Jin, Yuqi; Yang, Teng; Heo, Hyeonu; Krokhin, Arkadii; Shi, Sheldon Q.; Dahotre, Narendra; Choi, Tae-Youl; Neogi, Arup (September 2020, Polymers)

   null (Ed.)

   In this study, a novel ultrasonic non-destructive and non-invasive elastography method was introduced and demonstrated to evaluate the mechanical properties of fused deposition modeling 3D printed objects using two-dimensional dynamical elasticity mapping. Based on the recently investigated dynamic bulk modulus and effective density imaging technique, an angle-dependent dynamic shear modulus measurement was performed to extract the dynamic Young’s modulus distribution of the FDM structures. The elastographic image analysis demonstrated the presence of anisotropic dynamic shear modulus and dynamic Young’s modulus existing in the fused deposition modeling 3D printed objects. The non-destructive method also differentiated samples with high contrast property zones from that of low contrast property regions. The angle-dependent elasticity contrast behavior from the ultrasonic method was compared with conventional and static tensile tests characterization. A good correlation between the nondestructive technique and the tensile test measurements was observed. 

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2. Crystallographic texture dependent bulk anisotropic elastic response of additively manufactured Ti6Al4V

   https://doi.org/10.1038/s41598-020-80710-6  

   Pantawane, Mangesh V.; Yang, Teng; Jin, Yuqi; Joshi, Sameehan S.; Dasari, Sriswaroop; Sharma, Abhishek; Krokhin, Arkadii; Srinivasan, Srivilliputhur G.; Banerjee, Rajarshi; Neogi, Arup; et al (December 2021, Scientific Reports)

   null (Ed.)

   Abstract Rapid thermokinetics associated with laser-based additive manufacturing produces strong bulk crystallographic texture in the printed component. The present study identifies such a bulk texture effect on elastic anisotropy in laser powder bed fused Ti6Al4V by employing an effective bulk modulus elastography technique coupled with ultrasound shear wave velocity measurement at a frequency of 20 MHz inside the material. The combined technique identified significant attenuation of shear velocity from 3322 ± 20.12 to 3240 ± 21.01 m/s at 45 $$^\circ$$ ∘ and 90 $$^\circ$$ ∘ orientations of shear wave plane with respect to the build plane of printed block of Ti6Al4V. Correspondingly, the reduction in shear modulus from 48.46 ± 0.82 to 46.40 ± 0.88 GPa was obtained at these orientations. Such attenuation is rationalized based on the orientations of $$\alpha ^\prime$$ α ′ crystallographic variants within prior columnar $$\beta$$ β grains in additively manufactured Ti6Al4V. 

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3. Passive and Active Microrheology for Biomedical Systems

   https://doi.org/10.3389/fbioe.2022.916354  

   Mao, Yating; Nielsen, Paige; Ali, Jamel (July 2022, Frontiers in Bioengineering and Biotechnology)

   Microrheology encompasses a range of methods to measure the mechanical properties of soft materials. By characterizing the motion of embedded microscopic particles, microrheology extends the probing length scale and frequency range of conventional bulk rheology. Microrheology can be characterized into either passive or active methods based on the driving force exerted on probe particles. Tracer particles are driven by thermal energy in passive methods, applying minimal deformation to the assessed medium. In active techniques, particles are manipulated by an external force, most commonly produced through optical and magnetic fields. Small-scale rheology holds significant advantages over conventional bulk rheology, such as eliminating the need for large sample sizes, the ability to probe fragile materials non-destructively, and a wider probing frequency range. More importantly, some microrheological techniques can obtain spatiotemporal information of local microenvironments and accurately describe the heterogeneity of structurally complex fluids. Recently, there has been significant growth in using these minimally invasive techniques to investigate a wide range of biomedical systems both in vitro and in vivo . Here, we review the latest applications and advancements of microrheology in mammalian cells, tissues, and biofluids and discuss the current challenges and potential future advances on the horizon. 

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4. Manufacturing and Characterization of Hybrid Bulk Voxelated Biomaterials Printed by Digital Anatomy 3D Printing

   https://doi.org/10.3390/polym13010123  

   Heo, Hyeonu; Jin, Yuqi; Yang, David; Wier, Christopher; Minard, Aaron; Dahotre, Narendra B.; Neogi, Arup (January 2021, Polymers)

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   The advent of 3D digital printers has led to the evolution of realistic anatomical organ shaped structures that are being currently used as experimental models for rehearsing and preparing complex surgical procedures by clinicians. However, the actual material properties are still far from being ideal, which necessitates the need to develop new materials and processing techniques for the next generation of 3D printers optimized for clinical applications. Recently, the voxelated soft matter technique has been introduced to provide a much broader range of materials and a profile much more like the actual organ that can be designed and fabricated voxel by voxel with high precision. For the practical applications of 3D voxelated materials, it is crucial to develop the novel high precision material manufacturing and characterization technique to control the mechanical properties that can be difficult using the conventional methods due to the complexity and the size of the combination of materials. Here we propose the non-destructive ultrasound effective density and bulk modulus imaging to evaluate 3D voxelated materials printed by J750 Digital Anatomy 3D Printer of Stratasys. Our method provides the design map of voxelated materials and substantially broadens the applications of 3D digital printing in the clinical research area. 

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5. Active acoustic metamaterials with on-demand bulk modulus and full mass density tensor

   https://doi.org/10.1088/1361-665X/ad7550  

   Kovacevich, Dylan_A; Popa, Bogdan-Ioan (September 2024, Smart Materials and Structures)

   Abstract Active metamaterials address fundamental limitations of passive media and have widely been recognized as necessary in numerous compelling applications such as cloaking and extreme noise absorption. However, most practical devices of interest have yet to be realized due to the lack of a suitable strategy for implementing bulk active metamaterials—those that involve interacting cells and functionality beyond one dimension. Here, we present such an active acoustic metamaterial design with bulk modulus and anisotropic mass density that can be independently programmed over wide value ranges. We demonstrate this ability experimentally in several examples, targeting acoustic properties that are hard to access otherwise, such as a bulk modulus significantly smaller than air, strong mass density anisotropy, and complex bulk modulus and mass density for high reflectionless sound absorption. This work enables the transition of active acoustic metamaterials from isolated proof-of-concept demonstrations to versatile bulk materials. 

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