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The transient, dynamic response of soft materials to mechanical impact has become increasingly relevant due to the emergence of numerous biomedical applications, e.g., accurate assessment of blunt injuries to the human body. Despite these important implications, acceleration-induced pressure gradients in soft materials during impact and the corresponding material response, from small deformations to sudden bubble bursts, are not fully understood. Both through experiments and theoretical analyses, we empirically show, using collagen and agarose model systems, that the local pressure in a soft sample is proportional to the square of the sample depth in the impact direction. The critical acceleration that corresponds to bubble bursts increases with increasing gel stiffness. Bubble bursts are also highly sensitive to the initial bubble size, e.g., bubble bursts can occur only when the initial bubble diameter is smaller than a critical size (≈10 μm). Our study gives fundamental insight into the physics of injury mechanisms, from blunt trauma to cavitation-induced brain injury.

The dynamic response of cells when subjected to mechanical impact has become increasingly relevant for accurate assessment of potential blunt injuries and elucidating underlying injury mechanisms. When exposed to mechanical impact, a biological system such as the human skin, brain, or liver is rapidly accelerated, which could result in blunt injuries. For this reason, an acceleration of greater than > 150 g is the most commonly used criteria for head injury. To understand the main mechanism(s) of blunt injury under such extreme dynamic threats, we have developed an innovative experimental method that applies a well-characterized and -controlled mechanical impact to live cells cultured in a custom-built in vitro setup compatible with live cell microscopy. Our studies using fibroblast cells as a model indicate that input acceleration ( a in ) alone, even when it is much greater than the typical injury criteria, e.g., a in > 1 , 000 g, does not result in cell damage. On the contrary, we have observed a material-dependent critical pressure value above which a sudden decrease in cell population and cell membrane damage have been observed. We have unambiguously shown that (1) this critical pressure is associated with the onset of cavitation bubbles in a cell culture chamber and (2) the dynamics of cavitation bubbles in the chamber induces localized compressive/tensile pressure cycles, with an amplitude that is considerably greater than the acceleration-induced pressure, to cells. More importantly, the rate of pressure change with time for cavitation-induced pressure is significantly faster (more than ten times) than acceleration-induced pressure. Our in vitro study on the dynamic response of biological systems due to mechanical impact is a crucial step towards understanding potential mechanism(s) of blunt injury and implementing novel therapeutic strategies post-trauma.

In light of ongoing advancements in smart manufacturing, there is a growing need for intelligent fault diagnosis methods that maintain reliability under noisy, high-variability operating conditions. Conventional feature selection strategies often struggle when data contain outliers or suboptimal feature subsets, limiting their diagnostic utility. This study introduces a density-based feature space optimization (DBFSO) framework that integrates feature selection with localized density estimation to enhance feature space separability and classifier efficiency. Using k-nearest neighbor density estimation, the method identifies and removes low-density feature vectors associated with noise or outlier behavior, thereby sharpening the feature space and improving class discriminability. Experiments using roll-to-roll (R2R) manufacturing data under mechanical disturbances demonstrate that DBFSO improves classification accuracy by up to 36–40% when suboptimal feature subsets are used and reduces training time by 60–71% due to reduced feature space volume. Even with already-optimized feature sets, DBFSO provides consistent performance gains and increased robustness against operational variability. Additional validation using a bearing fault dataset confirms that the framework generalizes across domains, yielding improved accuracy and significantly more compact, noise-resistant feature representations. These findings highlight DBFSO as an effective preprocessing strategy for intelligent fault diagnosis in intelligent manufacturing systems.

The low thermal conductivity of phase change material (PCM) critically constrains the cooling performance of PCM-based battery thermal management system (BTMS). To address this limitation, embedding high-thermal-conductivity fins into PCM was recently explored. However, it may increase the overall BTMS mass, degrading vehicle performance. Therefore, a quantitative evaluation of the effects of fin design on cooling performance and system mass is required. In this study, the effects of fin design factors in a PCM–fin structured BTMS on the maximum cell temperature and BTMS mass was analyzed using design of experiments (DoE) and analysis of variance (ANOVA). To characterize BTMS thermal behavior, a numerical model was developed by applying thermal fluid partial differential equations (PDEs) with the enthalpy–porosity method to represent the phase change of the PCM. Fin number, thickness, and angle were selected as design factors; responses were calculated through thermal fluid analysis. The results showed a trade-off between thermal performance and mass across all design factors. The number of fins had the greatest effect on maximum cell temperature (78.27%) but less on mass (28.85%). Fin thickness moderately affected temperature (16.71%) but strongly increased mass (63.93%). Fin angle had minimal impact, 4.10% on temperature and 3.10% on mass.

Cavitation bubbles form in soft biological systems when subjected to a negative pressure above a critical threshold, and dynamically change their size and shape in a violent manner. The critical threshold and dynamic response of these bubbles are known to be sensitive to the mechanical characteristics of highly compliant biological systems. Several recent studies have demonstrated different biological implications of cavitation events in biological systems, from therapeutic drug delivery and microsurgery to blunt injury mechanisms. Due to the rapidly increasing relevance of cavitation in biological and biomedical communities, it is necessary to review the current state-of-the-art theoretical framework, experimental techniques, and research trends with an emphasis on cavitation behavior in biologically relevant systems (e.g., tissue simulant and organs). In this review, we first introduce several theoretical models that predict bubble response in different types of biological systems and discuss the use of each model with physical interpretations. Then, we review the experimental techniques that allow the characterization of cavitation in biologically relevant systems with in-depth discussions of their unique advantages and disadvantages. Finally, we highlight key biological studies and findings, through the direct use of live cells or organs, for each experimental approach.

Graphene–copper (Gr–Cu) composite conductors have demonstrated Gr‐enhanced electrical and thermal properties. However, the conductors’ coupled mechanical and electrical responses remain unexplored despite the importance of their mechanical flexibility and robustness. Here, the electromechanical behavior of a recently developed microscale Gr‐Cu composite, called axially continuous graphene–copper (ACGC) wire, has been investigated by developing and utilizing a customized tensile testing method. Experimental studies have shown that 80 μm‐diameter ACGC (hereafter ACGC80) wires exhibit 3.681% and 3.173% higher compared to as‐received and annealed Cu wires, respectively. More importantly, the Gr‐enhanced electrical performance of the ACGC80 has been observed even after significant plastic deformation under uniaxial tension. To be specific, the conductivity of ACGC80 is 3.139%, 3.144%, and 3.088% higher than that of annealed copper wire at 3, 6, and 9% strain, respectively. Analysis indicates that ACGC80 deforms by forming highly localized plastic deformation zones along its length. This result suggests that graphene in ACGC80 serves as an effective electron pathway even after applying a large strain because the pronounced damage to graphene is limited to only a small fraction of ACGC80. The ACGC80 conductor has great potential to advance emerging applications in flexible interconnects, wearable electronics, and high‐power transmission for microchips. This study investigates the electromechanical behavior of 80 μm‐diameter axially continuous graphene–copper (ACGC80) wires by developing a customized tensile testing method. Experimental studies have shown that ACGC80 wires exhibit higher electrical conductivity compared to as‐received and annealed Cu wires, and more importantly, the Gr‐enhanced electrical performance of the ACGC80 has been observed even after significant plastic deformation under uniaxial tension.

The purpose of this study was to develop and characterize a novel fluorescence-based retention assay for the evaluation of the release profile of bone morphogenetic protein-2 (BMP-2) released from bone graft carrier. In this study, we evaluated the binding, release kinetics, and delivery efficacies of BMP-2 incorporated into hydroxyapatite (HA) bone grafts. The evaluation of the release profile of BMP-2 from HA bone grafts using a fluorescence-based retention assay revealed initial burst releases from the HA bone grafts followed by long sustained releases up to 14 weeks. The sustained biological activity of the released BMP-2 from HA bone grafts over the full 14-week period supports a long sustained mechanism via fluorescence-based retention assay. Thus, the results from this study show that BMP-2 could be incorporated into HA bone grafts for sustained release over a prolonged period of time with retention of bioactivity and our fluorescence-based retention assay, which is principally detecting the retention profile of BMP-2 in HA bone grafts, is more accurate than conventionally collecting the released BMP-2 for evaluation of BMP-2 release profiles.

Fibroblast growth factor18 (FGF18) belongs to the FGF family and is a pleiotropic protein that stimulates proliferation in several tissues. Bone marrow mesenchymal stem cells (BMSCs) participate in the normal replacement of damaged cells and in disease healing processes within bone and the haematopoietic system. In this study, we constructed FGF18 and investigated its effects on rat BMSCs (rBMSCs). The proliferative effects of FGF18 on rBMSCs were examined using an MTS assay. To validate the osteogenic differentiation effects of FGF18, ALP and mineralization activity were examined as well as osteogenic differentiation-related gene levels. FGF18 significantly enhanced rBMSCs proliferation (p<0.001) and induced the osteogenic differentiation by elevating ALP and mineralization activity of rBMSCs (p<0.001). Furthermore, these osteogenic differentiation effects of FGF18 were confirmed via increasing the mRNA levels of collagen type I (Col I), bone morphogenetic protein 4 (BMP4), and Runt-related transcription factor 2 (Runx2) at 3 and 7 days. These results suggest that FGF18 could be used to improve bone repair and regeneration.

Growth factors (GFs) such as BMPs, FGFs, VEGFs and IGFs have significant impacts on osteoblast behavior, and thus have been widely utilized for bone tissue regeneration. Recently, securing biological stability for a sustainable and controllable release to the target tissue has been a challenge to practical applications. This challenge has been addressed to some degree with the development of appropriate carrier materials and delivery systems. This review highlights the importance and roles of those GFs, as well as their proper administration for targeting bone regeneration. Additionally, the and performance of those GFs with or without the use of carrier systems in the repair and regeneration of bone tissue is systematically addressed. Moreover, some recent advances in the utility of the GFs, such as using fusion technology, are also reviewed.

Fibroblast growth factor 2 (FGF2) protein plays important roles in wound healing and tissue regeneration. Collagen is clinically used for wound care applications. We investigated the potential value of FGF2-functionalized collagen matrices for skeletal muscle tissue engineering. When C2C12 cells were treated with FGF2, cell adhesion increased after 3 and 5 days compared to the control (P < 0.05). Wound healing activity of FGF2 was slightly higher than the control through cell migration. Cell proliferation activity of FGF2-functionalized collagen matrices on C2C12 cells also increased. Taken together, FGF2 stimulated C2C12 myoblast growth by promoting cell adhesion, proliferation and wound healing activity after injury. The potential effect of FGF2-functionalized collagen matrices was also observed. Thus FGF2 stimulates skeletal muscle development and regeneration, thereby leading to potential utility for skeletal muscle tissue engineering.