The microstructure of cellular materials, in particular microcellular polymers, is commonly characterized by the mean cell size and cell population density. Although the physical properties of foamed polymers are highly dependent on cell distribution, very insignificant work has been carried out to quantify the distribution of cells. This experimental study correlates the influential processing parameters of microcellular injection molding with the cell distribution, mean cell size and population density. For the first time, “Cell Distribution Index (CDI)”, a quantitative parameter for characterization of foams has been defined in this paper. Foamed samples of polystyrene were prepared via microcellular injection molding process. The design of experiment includes five influential processing parameters (factors) at five different levels. Molded samples were fractured cryogenically and micrographs were obtained using a table top scanning electron microscope. With the help of image processing package, mean cell size, cell population density, frequency and newly defined term CDI were calculated for each micrograph. Finally, the effect of processing parameters on cell distribution was analyzed by plotting the CDI against the processing parameters.
The selective manipulation and incubation of individual picoliter drops in high-throughput droplet based microfluidic devices still remains challenging. We used a surface acoustic wave (SAW) to induce a bubble in a 3D designed multi-trap polydimethylsiloxane (PDMS) device to manipulate multiple droplets and demonstrate the selection, incubation and on-demand release of aqueous droplets from a continuous oil flow. By controlling the position of the acoustic actuation, individual droplets are addressed and selectively released from a droplet stream of 460 drops per s. A complete trapping and releasing cycle can be as short as 70 ms and has no upper limit for incubation time. We characterize the fluidic function of the hybrid device in terms of electric power, pulse duration and acoustic path.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.