In recent years, a minimally invasive medical needle is required. The development of such a fine needle requires evaluation of puncture resistance force. We have developed various microneedles and conducted the puncture experiments to evaluate their resistance force against an artificial skin made of silicone rubber. In this study, it is attempted to reproduce the puncture experiment by FEM simulation, in which accurate three dimensional (3D) models of needle and skin are constructed, and the conditions of material properties, model size, puncture distance, puncture speed, etc. are set to the same ones as the experiments. As a commercially available nonlinear FEM software, LS-DYNA was employed. The results of FEM analysis and those of experiment were compared to estimate what extent they are matched. As a result, the tendency of the load curve, i.e., transition of resistance force with respect to puncturing distance, and the state of skin deformation were well matched, showing the possibility of FEM analysis to reproduce the experiment. The error of resistance force between analysis and experiment was 20% at most. It is expected that the parameter study would be possible, in which the performance of needle is evaluated by changing the parameters, e.g., its size, shape, how to insert it to the skin, etc.

In our previous paper, to simulate mosquito flapping flight, experiments were performed using a wing model, which had n-times (n=10) enlarged shape of the mosquito wing and was made of deformable elastic material. The similarity conditions of the flows around the model and mosquito wings were satisfied by means of the Reynolds number and Strouhal number. In order to satisfy the similarity condition of wing deformation, it was considered that the Cauchy number of the model and the real case are identical. As a result, the relationship EI =n²E_mI_m was obtained, where EI is the bending rigidity of the wing, and no-subscript and subscript m denote the model and mosquito wings, respectively. However, according to the experimental results, the deformation similarity was satisfied when EI = E_mI_m. This phenomenon was analyzed by means of vectorial dimensional analysis and discriminated dimensional analysis. On the similarity of flapping wings with bending deformation, two independent dimensionless parameters majorly influence the results: Cauchy number and mass ratio. If a relationship between these quantities could be derived, it would be possible to understand the similarity condition by means of a unique dimensionless parameter. Based on this consideration, a combined dimensionless parameter Π was derived considering the experimental results. It was shown that, by matching the parameter Π between the model and mosquito wings, deformation similarity was possible and the conflicting results on bending rigidity were resolved.

Vascular smooth muscle cells (VSMCs) actively remodel the arterial walls through biomechanical signals and dedifferentiate from the contractile to the synthetic phenotype under pathological conditions. It is important to elucidate the mechanism underlying phenotypic transition of VSMCs for understanding their role in the pathophysiology of disease and for developing engineered tissues. Although numerous studies have reported various biochemical or biomechanical factors that stimulate the phenotypic transition of VSMCs, very little is known about the changes in the mechanical environment of intracellular nucleus that are involved in various cellular functions. This study investigated the changes in the force exerted on the intracellular nucleus, and their morphology and mechanical properties during serum starvation-induced VSMC differentiation. Fluorescent microscopy image analysis and atomic force microscopy nano-indentation live cell imaging revealed that the serum-starvation culture conditions markedly promote the contractile differentiation of VSMCs with F-actin stabilization and reduces the internal force exerted on the nucleus. The nuclei in these contractile VSMCs exhibited surface stiffening and matured nuclear lamina. Additionally, the nuclei exhibited distinct surface dimples along the actin stress fibers even though these nuclei were exposed to lower internal forces. These results indicate that the distinct dimples on the nuclear surfaces represent a plastic remodeling of the nucleus under the serum-starvation culture conditions. The nuclear stiffening, local deformation, and plastic remodeling observed in this study may be important factors in contractile differentiation of VSMCs.

The use of various types of information devices equipped with touch panels has been increasing. When these devices are used directly with fingers, the devices become dirty owing to sweat and oil from users. Therefore, there is considerable interest in keeping the surfaces of devices free from fingerprints and dirt. Antifouling films and coatings are being developed for this purpose. In addition, a method of changing the surface shape by adding a microstructure to a material surface has been developed. The purpose of this study is to add the antifouling function to glass surfaces using a mechanical removal process. We attempted to change the surface shape by processing a material surface directly. The processing method was microslurry-jet (MSJ) processing, which is a mechanical removal method. In addition, a masking process was used to create microsurface structures. As an example, we evaluated the anti-fingerprint glass created by these processing methods. Microsurfaces were successfully created on the glass surface through the combination of the masking process and MSJ processing. Moreover, the visibility of the created glass, surface characteristics, friction characteristics, and the adhesion of stains were evaluated. With respect to visibility, surface characteristics, and adhesion, it was possible to observe the changes in surface characteristics due to the microsurfaces. With regard to friction characteristics, differences in surface patterns were found for individual subject data.