A two-step method for fabricating large-area textile-embedded elastomers for tunable friction.

Recently, shape-tunable wrinkles formed on an elastomeric sheet with a textile finely embedded in proximity to the surface have been developed for in situ control of friction depending on various situations. For their actual uses, sheets with a large area are desired. A key challenge on their fabrication is to overcome the non-uniformity of the vertical position of the textile embedded within the elastomeric sheet, which causes substantial reduction in the tunable range of friction. The defect originates from the increased difficulty, as the sheet area is scaled up, of squeezing a viscoelastic precursor liquid due to the use of a deformable elastomeric surface. Here, we report a new two-step method for a textile-embedded elastomeric sheet that avoids using the soft elastomeric surface on the squeezing process and requires post-joining to an elastomeric base sheet. The obtained sheet with a large area (180 × 180 mm), was uniform and showed a large change of friction on its strain-induced transformation between flat and wrinkled states. The relationship between the experimentally controllable parameters and the squeeze film hydrodynamics is theoretically discussed, which is generally applicable to precise embedding micro-objects at the elastomer surface.

Arrayed three-dimensional structures designed to induce and maintain a cell pattern by a topographical effect on cell behavior.

We investigated the ability of the microscale topography of a three-dimensional (3-D) structure arrayed on the surface of a substrate to induce and maintain a cell pattern by controlling cell behavior. Arrayed 3-D structures having different topographical characteristics, i.e., geometry and dimension, were fabricated on the surface of glass substrates by masked sand blasting. Each 3-D structure was designed to have a unit composed of a planar island for cell growth and surrounding grooves exhibiting cell repellency. The principle of the cell repellency is based on the topographical control of cell attachment, spreading, growth, and differentiation by utilizing the spatially restricted microenvironment of the grooves. Grooves with a width of less than approximately 116µm and a depth of approximately 108µm formed narrow V-shapes with a dihedral angle of less than approximately 44.4°. Cell culture experiments using osteoblast-like cells demonstrated that these narrow V-shaped grooves had sufficient cell repellency to form and maintain a cell pattern on the surface for at least 14days. From the present study, arrayed 3-D structures designed to have narrow V-shaped grooves with optimal topographical characteristics for cell repellency are promising for the formation of stable cell patterns for creating novel cell microarray platforms without using conventional protein/cell-repellent chemicals.

Evaluation of the capacity of mosaic-like porous ceramics with designed pores to support osteoconduction.

Under osteoconductive conditions, porous calcium phosphate ceramics are known to induce new bone formation within their pores. A critical aspect of the design of porous ceramics is the geometrical features of their pores, with regard to promoting bone formation and mass transfer management in pore networks. However, the pore geometries of common porous ceramics lack clear details. Further, the connections between pores are hard to characterize and thus have not been thoroughly researched. To address these issues, we have developed an original method for fabricating porous ceramics, which we have termed "mosaic-like ceramics fabrication (MLCF)." Using MLCF, pore geometries can be designed and fabricated by each unit, and a network covering all the pores can be fabricated. Furthermore, MLCF can be used to build porous ceramics with custom-made shapes. In this study, we assessed the osteogenic influences of MLCF products (MLPC) composed of hydroxyapatite units on the differentiation of rat bone-marrow-derived mesenchymal stem cells (MSCs) in vitro and in vivo. Two types of commercial porous artificial bone were used as positive controls. MLPC was superior in osteogenic potential, and proved to be a reliable scaffold for bone tissue engineering. Furthermore, this study succeeded in defining the important geometries for osteoconduction.

Peri-implant bone density in senile osteoporosis-changes from implant placement to osseointegration.

PURPOSE: The aim of this study was to examine healing over time after implant body placement in a senile osteoporosis model and a control group. MATERIALS AND METHODS: In this study, 16-week-old male mice were used. The senile osteoporosis model consisted of senescence-accelerated prone 6 mice and the control group consisted of senescence-accelerated resistant 1 mice. Titanium-coated plastic implants were used as experimental implants whose dimensions were 3.0 mm in length, 1.1 mm in apical diameter, and 1.2 mm in coronal diameter. Bone samples were collected at 5, 7, 14, 21, and 28 days after implant placement. A micro-quantitative computed tomography (QCT) system was used to scan these samples and a phantom in order to quantitate bone mineral measurements. Bone mineral density (BMD) of each sample was measured. Each sample was also examined by light microscopy after QCT imaging. At 14 and 28 days after implant placement, the bone-implant contact (BIC) ratios were calculated from light microscopy images and were divided into cortical bone and bone marrow regions. RESULTS: When BMD was compared between the osteoporosis and control groups using micro-QCT, the osteoporosis group had a significantly lower BMD in the region 0-20 µm from the implant surface in the bone marrow region at 14 days onward after implant placement. Compared with the control group, the osteoporosis model also had significantly lower BMD in all regions 0-100 µm from the implant surface in the bone marrow region at 14 days after placement. However, in the cortical bone region, no statistically significant difference was observed in the regions at the bone-implant interface. Light microscopy revealed osseointegration for all implants 28 days after implant placement. The osteoporosis model tended to have lower BICs compared with that of the control group, although this did not reach statistical significance. DISCUSSION: Our results showed that osseointegration was achieved in the osteoporosis model. However, the BMD was 30-40% lower than that of the control group in the region closest to the implant surface in bone marrow region. Peri-implant BMD was lower in a relatively large area in the osteoporosis model during an important time for osseointegration. Therefore, this result suggests that osteoporosis might be considered as a risk factor in implant therapy. CONCLUSION: The osteoporosis model had a lower BMD than the control group in the region closest to the implant during an important time for osseointegration. This result suggests that senile osteoporosis might be a risk factor in implant therapy. However, the osteoporosis model and the control group had no difference in peri-implant BMD in the cortical bone region. This suggests that risk might be avoided by implant placement that effectively uses the cortical bone.