Directed cell migration is critical to a variety of biological and physiological processes. Although simple topographical patterns such as parallel grooves and three-dimensional post arrays have been studied to guide cell migration, the effect of the dimensions and shape of micropatterns, which respectively represent the amount and gradient of physical spatial cues, on cell migration has not yet been fully explored. This motivates a quantitative characterization of cell migration in response to micropatterns having different widths and divergence angles. The changes in the migratory (and even locational) behavior of adherent cells, when the cells are exposed to physical spatial cues imposed by the micropatterns, are explored here using a microfabricated biological platform, nicknamed the "Rome platform". The Rome platform, made of a biocompatible, ultraviolet (UV) curable polymer (ORMOCOMP), consists of 3 μm thick micropatterns with different widths of 3 to 75 μm and different divergence angles of 0.5 to 5.0°. The migration paths through which NIH 3T3 fibroblasts move on the micropatterns are analyzed with a persistent random walk model, thus quantifying the effect of the divergence angle of micropatterns on cell migratory characteristics such as cell migration speed, directional persistence time, and random motility coefficient. The effect of the width of micropatterns on cell migratory characteristics is also extensively investigated. Cell migration direction is manipulated by creating the gradient of physical spatial cues (that is, divergence angle of micropatterns), while cell migration speed is controlled by modulating the amount of them (namely, width of micropatterns). In short, the amount and gradient of physical spatial cues imposed by changing the width and divergence angle of micropatterns make it possible to control the rate and direction of cell migration in a passive way. These results offer a potential for reducing the healing time of open wounds with a smart wound dressing engraved with micropatterns (or microscaffolds).
NOMENCLATURE D = chamber diameter H = chamber height d 1 = diffuser inlet width d 2 = diffuser outlet width d 3 = air inlet channel width d 4 = air inlet gate length d 5 = air outlet channel width dh = diffuser lengthIn this paper, we propose a synthetic jet-type micropump for supplying air. Synthetic jet actuators usually include a small single pumping cavity, inlet/outlet channels, and a Lead zirconate titanate(PZT) membrane that exerts the pumping pressure. To determine the optimum design parameters of the air pump, a numerical analysis was carried out by varying its geometry. The optimized air pump was fabricated by replicating PDMS parts from silicon masters patterned by the deep RIE process. The size of the fabricated micropump was 16 × 13 × 3 mm 3 . In order to control the frequency of the PZT membrane and reduce the controller size and power consumption, an SP4423 microchip was used. At a pumping frequency of 80 Hz, a flow rate of 9.5 cc/min, pumping pressure of 438 Pa, and power consumption less than 0.15 mW were achieved.
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