Scaffold based tissue engineering strategies use cells, biomolecules and a scaffold to promote the repair and regeneration of tissues. Although scaffold-based tissue engineering approaches are being actively developed, most are still experimental, and it is not yet clear what defines an ideal scaffold/cell construct. Solid free form fabrication (SFF) techniques can precisely control matrix architecture (size, shape, interconnectivity, branching, geometry and orientation). The SFF methods enable the fabrication of scaffolds with various designs and material compositions, thus providing a control of mechanical properties, biological effects and degradation kinetics. This paper reviews the application of micro-robotics and MEMS-based fabrication techniques for scaffold design and fabrication. It also presents a novel robotic technique to fabricate scaffold/cell constructs for tissue engineering by the assembly of microscopic building blocks.
International audienceWe present an experimental study of a new regime of monodisperse micro-droplet generation that we named the balloon regime. A dispersion of oil in water in a T-junction microfluidic system was studied. Several microfluidic devices having different cross-sections of the continuous and the dispersed phases micro-channels were tested. This new regime appears only for low- dispersed phase velocity. The micro-droplet size is mainly related to the geometry of the T-junction micro-channels especially its width and depth, and independent of the continuous and dispersed phases velocities. In our experiments, the velocities of the continuous and the dispersed phases vc and vd respectively, have been varied in a wide range: vc from 0.5 to 500 mm/s, and vd from 0.01 to 30 mm/s. We show that the continuous phase only controls the micro-droplet density, while the dispersed phase linearly changes the frequency of the micro-droplet generation. Another particularity of the present regime, which differentiates it from all other known regimes, is that the micro-droplet retains its circular shape throughout its formation at the T junction, and undergoes no deformation due to the drag forces. We propose a mechanism to explain the formation of microdroplets in this new regime
Abstract-This paper reports a novel optofluidic sensor for measuring dynamic interfacial tensions. The field of micro optofluidics utilizes both microfluidic and microoptic technologies. Thus, our sensor consists of a mirofluidic network and an optical detection system. The sensor is able to measure both surface tension or liquid/liquid interfacial tension. In the case of surface tension measurement, the liquid sample is introduced into a main channel, while air is injected through a T-junction. In the case of liquid/liquid interfacial tension measurement, a second immiscible liquid such as oil is introduced into a main channel, while the sample liquid is injected through the T-junction. The formation frequency of the micro bubbles or micro droplets represent the interfacial tension between the two phases. This frequency can be measured easily by optical detection. Measurements were carried out for aqueous solutions with different concentrations of the ionic surfactant CTAB (Cetyl Trimethyl Ammonium Bromide). The actual interfacial tensions of these solutions were calibrated with a commercial tensiometer (FTA200, First Ten Angstrom). The measurement results show a clear relation between the interfacial tension and the formation frequency. Furthermore, our sensor can be used to identify the critical micelle concentration (CMC) of a surfactant. The sensor potentially allows the use of a minute amount of sample compared to the relatively large amount required for existing commercial systems.Index Terms-micro optofluidics, microfluidics, interfacial tension, lab on a chip.
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