Design of a novel MEMS platform for the biaxial stimulation of living cells.

Micromechanical systems are increasingly being used as tools in biological applications, since their characteristic dimensions permit to operate at the same length scale of the structures under investigation. Here, we present a methodology for the design, fabrication and operation of a tool for the assessment of mechanical properties of single cells. In particular, we describe a microsystems platform to study bio-mechanical response of single living cells to in-plane biaxial stretching. The proposed device employs a new linkage design in order to obtain the displacement of the quadrants of a sliced circular plate in mutually-orthogonal directions using just one linear actuator. With this linkage geometry, the whole device has only one degree of freedom. This results in a very predictable and reliable mechanical behaviour, thereby allowing use a simple and easily available control electronics. Results of this study have relevance for the design of a powerful yet simple BioMEMS platform for the characterization of living cells as in-plane bi-axial loading simulated the conditions experienced by cells in vivo more realistically than a uniaxial stretching.

Modeling of a microfluidic channel in the presence of an electrostatic induced cross-flow.

Amongst the processes that have been implemented in microfluidic devices, electrophoretic transport of charged molecules, along microfluidic channels, is one of the most commonly found. However, less work has been done about continuous, pressure gradient driven flow systems where an electric field is applied orthogonally with respect to the microchannel walls. The perspective applications of this technique, include continuous flow separation and concentration of analyte molecules, and the kinetic control of surface reactions. In order to dimensioning and optimizing such a device, a mathematical model has been formulated and analyzed both with numeric and analytic methods. The given solutions let the designer of microfluidic devices able to estimate the concentration profiles along the microchannel length, as a function of the main system parameters. As a practical example of application which could be of great interest in biotechnology applications, the results relative to the simulation of the electrostatic induced cross flow of single strand DNA oligonucleotides of about 20 bases has been reported.

Porous titanium obtained by a new powder metallurgy technique: Preliminary results of human osteoblast adhesion on surface polished substrates.

This study concerns a novel powder metallurgy method for producing porous titanium (pTi) exhibiting high mechanical properties. The preparation procedure consisted of the following stages: first, the preparation of Ti and titanium hydride (TiH2) powder mixtures and their consolidation with a cold isostatic press, followed by a sintering of the green bodies performed with hot isostatic press (HIP) equipment. Thermal decomposition in controlled environment of the TiH2 phase results in the foam structure. The resulting porosity percolates with a volume fraction of approximately 20%. The final material exhibits interesting mechanical properties, comparable to those of full density titanium (between grade 2 and grade 3), with the advantage of a minor density. The samples produced were tested to verify their biological response by studying the effectiveness of osteoblast adhesion and growth. In this preliminary study, osteoblastic cell morphology was investigated and compared to that observed on fully dense commercially pure titanium (Ti-cp) (ASTM, grade 3). The preliminary results were promising regarding cellular adhesion and spreading. (Journal of Applied Biomaterials & Biomechanics 2003; 1: 172-7).

[Burrs breaking in oral surgery: a experimental study]. / Frattura delle frese in chirurgia orale: valutazione sperimentale.

BACKGROUND: This experimental work came out from clinic observations. The deal is to check the factors that can provoke the fracture of the more commonly in oral surgery used burrs, and then reduce the correlated risks to this event. Besides a fracture surface characterisation is done to point out the presence of production and/or stoking defects that can alter the structure. METHODS: Four batches of new surgical burrs (type Lindemann) were examined for a total of 40 samples. The first batch was used as control, the other three were submitted to 5, 10 and 20 sterilisation cycles respectively. Before each cycle disinfectant washing was done. All the samples were then mechanical tested (four point bending test) for the determination of the ultimate tension strength. The fracture surfaces were observed at SEM; a comparison with that of burrs broken during surgery operations was done. RESULTS: The new burrs did not show working defects. The washing and sterilisation processes did not provoke any corrosion attack. CONCLUSIONS: No significant differences among the batches were detected from the mechanical tests as well as from micrographic observations.