Porous poly-L-lactide acid (PLA) scaffolds are prepared using polymer sintering and porogen leaching method. Different weight fractions of the Hydroxyapatite (HA) are added to the PLA to control the acidity and degradation rate. The three dimensional morphology and surface porosity are tested using micro CT, optical microscopy and scanning electron microscopy (SEM). Results indicate that the surface porosity does not change by addition of HA. The micro Ct examinations show slight decrease in the pore size and increase in wall thickness accompanied with reduced anisotropy for the scaffolds containing HA. SEM micrographs show detectable interconnected pores for the scaffold with pure PLA. Addition of the HA results in agglomeration of the HA which blocks some of the pores. Compression tests of the scaffold identify three stages in the stress-strain curve. The addition of HA adversely affects the modulus of the scaffold at the first stage, but this was reversed for the second and third stages of the compression. The results of these tests are compared with the cellular material model. The manufactured scaffold have acceptable properties for a scaffold, however improvement to the mixing of the phases of PLA and HA is required to achieve better integrity of the composite scaffolds.

The hygro-mechanical properties of bio-fiber composites comprise two aspects: the coupling between moisture diffusion and mechanical deformations and the coupling of moisture contents and the constitutive behaviors. Bio-fiber is hydrophilic, which absorbs water promptly when environmental moisture content increases; as the moisture content in the fiber increases, its mechanical properties decrease. This paper presents a series of micromechanical simulations to predict the hygro-mechanical behaviors of woodfiber-reinforced plastic composites considering the effects of fiber arrangements on the stress-strain relations and moisture-expansions on three progressively constructed constitutive configurations: 1) the fiber is elastic orthotropic and expandable under moisture variations; the plastic matrix is elastic isotropic and insensitive to environmental moisture variations, and the interface between fiber and matrix is perfectly bounded; 2) the plastic matrix is hyperelastic and expresses a certain degree of damage as deformation progresses; and 3) the interface has a pseudo adhesive layer that obeys Smith and Ferrante's universal binding law implemented as a cohesive zone model in the micromechanical simulation. In configuration II, micromechanical simulations demonstrate significant reductions in the nominal elastic modulus of composites when a nonlinear elastic model for the polymer matrix is assumed. The prediction for stress-strain relationship is found to be comparable to the experimental measurements. A cohesive model in configuration III is introduced to evaluate the possible moisture degradation to the fiber-matrix interface, which results in a reduction in elastic modulus and failure strength of the composite s, as observed in experiments. The cohesive zone model parameters as a function of moisture content in the composites requires more attention in model correlation and guarantee more direct experimental observations.

This paper examines the effect of plastic deformation on the strength and transformation heat and temperatures of the superelastic Nitinol samples. Two types of compression tests and differential scanning calorimetry tests were conducted. The first type of compression test deformed the samples to final fracture, and the second type included two loading –unloading cycles with or without plastic deformation. The mechanically tested samples were analyzed using differential scanning calorimetry.

The micro-mechanical properties of 5 μm thick histological sections of ferret aorta and vena cava were mapped as a function of distance from the outer adventitial layer using nanoindentation. In order to decouple the effect of the glass substrate on the elastic modulus of these thin sections, the nanoindentation data were analyzed using the extended Oliver and Pharr method which is readily accessible for coatings and layered materials with the software package, FilmDoctor®. In the aorta, the elastic modulus was found to decrease progressively from 35 MPa at the adventitia (outermost layer) to 8 MPa at the intima (innermost layer). This decrease in modulus was inversely correlated with elastic fibre density. In contrast, in the vena cava, the stiffest regions were found to be the adventitial (outer) and intimal (innermost) sections of the vessel cross-section. Both these regions were enriched in ECM components. The central region, thought to be largely cellular, had a relatively constant modulus of around 20 MPa. This study demonstrates that with this methodology it is possible to distinguish micro-mechanically between large arteries and veins, and therefore the same approach should allow age or disease related changes in the mechanical properties within a tissue to be quantified.

Mechanics play a critical role in cell function in health and disease. While a variety of techniques exist to measure cell mechanics, no single device or testing method can answer all biomechanics questions. We have designed a novel dielectrophoretic cell mechanics device to apply piconewton forces to single, asymmetric attached cells without physical contact. This device uses negative dielectrophoresis to trap individual cells, after which cells attach to the device substrate. Negative dielectrophoresis is then used to apply compressive force to attached cells, and cell displacement is measured via microscopy.

COMSOL software was used to model the two-dimensional electric and force fields. Based on modeling results, a quadrupole electrode configuration was designed in AutoCad,fabricated using microfabrication techniques, and tested with endothelial cells. A modeled quadrupole electrode with a 50 μm center diameter operating at 1 volt and 1 MHz generated 100's piconewtons of compressive force. This force was sufficient to trap both polystyrene beads and cells. While trapped cells did attach to the glass substrate, further refinement of the device is needed to maintain the cells in a healthy state.

This dielectrophoretic mechanics testing device expands the existing biomechanics toolbox by providing a non-contact method to test mechanics of attached cells under diverse conditions. Future dielectrophoretic systems could allow tensile as well compressive forces, and when coupled with microfluidic systems, could test cell mechanics under fluid flow or a chemotactic gradient. This device will improve our understanding of cell mechanics in healthy cell function and how perturbation of the mechanical environment contributes to disease.

Cell-implant adhesive strength is important for prostheses. In this paper, an investigation is described into the adhesion of bovine chondrocytes to Ti6Al4V-based substrates with different surface roughnesses and compositions. Cells were cultured for 2 or 5 days, to promote adhesion. The ease of cell removal was characterised, using both biochemical (trypsin) and mechanical (accelerated buoyancy and liquid flow) methods. Computational fluid dynamics (CFD) modelling has been used to estimate the shear forces applied to the cells by the liquid flow. A comparison is presented between the ease of cell detachment indicated using these methods, for the three surfaces investigated.

The molecular composite composed of polyethylene (PE) and poly(vinyl acetate) (PVAc) prepared using supercritical carbon dioxide (scCO2) and its surface modification for biocompatible surface demonstrated the creation of novel polymer biomaterials. In this study, this modification process was applied to the PE narrow tube (inside diameter: 300μm, outside diameter: 600μm, length: 5m). It was confirmed that PVAc was uniformly generated in PE tube by infrared imaging measurement of cross-section. After the acetyl group on the surface was hydrolyzed, phospholipid polymer was immobilized to the hydroxyl group on the surface of the tube. The phospholipid polymer immobilized surface showed a drastic reduction in protein adsorption. The surface of the minute and slender tube can be effectively modified using the feature of carbon dioxide whose surface tension is near zero. The modification technology by scCO2 is a promising for creation of variously-shaped new biomaterials.

The evolution of dental ceramics over the past four decades has been remarkable in light of the increase in the diversity of materials and fabrication techniques that have become available. As a consequence, the applications and indications for all-ceramic materials continue to expand. The purpose of the present article is to review the evolution of dental ceramics from the various aspects of crystalline phases, glassy matrix, flaws and in vivo performance.

In this paper, we proposed a novel miniaturized cell stretching tool using an Ionic Polymer-Metal Composites (IPMC) actuator. An IPMC is small, light weight and can be fabricated in any shape. And it drives flexibly like a living thing by low voltage. In this study, the PDMS chamber with PDMS membrane of 20 μEm thick for cell culturing had been fabricated on IPMC. And cultured cells were stretched by IPMC. The displacements of PDMS membrane were measured by a laser displacement sensor. And then, cells were cultured on PDMS membrane and stretched them by the motion of IPMC in an incubator. The results show that the PDMS membrane and cells were stretched by IPMC. This is the first fabrication of a cell stretching tool using IPMC. The potentiality of cell stretching tool using IPMC was demonstrated.

Metacarpophalangeal (MCP) joint proximal bone-cartilage specimens from the fourth digit were collected from repetitively flexed and non-flexed (control) paws of four New Zealand White rabbits. The specimens were cryo-fractured to reveal a sagittal cut containing the cartilage zones of different collagen microstructure. Nanoindentation, Fourier Transform infrared microspectroscopic imaging (FTIRMI), and histology were performed on a region of interest (ROI) ∼400 microns wide and through the thickness of the cartilage with two goals in mind: (1) to examine the effect of collagen network structure (random in the mid zone versus organized in the deep zone) on the biomechanical and biochemical properties of cartilage; and (2) to understand the changes in these properties due to physical forces. We found that zone microstructure significantly affected the measurement of the local relaxed modulus measured by nanoindentation. The deep zone had a higher modulus than the mid zone (Wilcoxon paired test, p<0.05). We also found that flexion significantly decreased the proteoglycan content in both the mid and deep zones (Wilcoxon paired test, p<0.05), suggesting indirect repetitive loading in the rabbit paw can be damaging to the joint via down regulating proteoglycan synthesis in the mid and deep zone cartilage. This is the first study to simultaneously report the local zone-specific mechanical and biochemical properties in the rabbit joint flexion model.

Chemical gardens are biomimetic structures in the form of plants formed by a combination of salts which precipitate by a combination of convection forced by osmosis, free convection and chemical reactions. Chemical gardens may be implicated in other phenomena of industrial interest which involve precipitation across a colloidal gel membrane which separates two different aqueous solutions, for example, in cement technology and metal corrosion process. However, the variation in chemical composition, morphology and mechanical properties of the different surfaces of these formations is not well known yet. Several salts in different concentrations and conditions have been explored under terrestrial gravity and microgravity. The chemical garden structures have been characterised by morphology analysis, scanning electron microscopy, chemical analysis and x-ray diffraction, correlating these data with the biomimetic growth and the physical-chemical nanoprocesses involved in it. This approach can also be useful for the analysis of biomaterials with interesting biomechanical properties.