Facile Adaptation of a Fused Deposition Modeling 3D Printer to Motionless Printing through Programmable Electric Relay: Discretized Modeling and Experiments.

In this study, a fused deposition modeling 3D printer is modified into a motionless printer, which has the potential to print patterns in a noiseless manner possibly with improved resolution and in less delay time by eliminating the movement of nozzle or collector. In this motionless 3D printer, both nozzle and collector are fixed, whereas the extruded polymer melt is driven by high-voltage switching points on the collector. By this approach, simple 3D patterns such as multilayer circles, squares, and walls have been printed using two polymer melts with different rheological properties, high-temperature polylactic acid and acrylonitrile butadiene styrene. Furthermore, a discretized, nonisothermal bead and spring model is developed to probe printing patterns. The effect of parameters, such as number of conducting points, switching time, voltage and material properties on the accuracy of the printed simple 3D patterns, are thoroughly studied, and we demonstrated that various fiber collection patterns obtained from the experiments are favorably compared with the simulation results.

Control of formation of viscoelastic droplets and distribution of nano-inclusions in functional deposition for lithium-sulfur batteries.

The electrospray process produces micro/nanodroplets for various applications such as thin and uniform coatings, drug carriers and mass spectrometry. In this paper, we study the spray processes of viscoelastic jets using simulations and experiments. In discretized modeling, the jet is perturbed with axisymmetric instability and the growth of this instability causes the jet to break into droplets. For the experiments, a solution of polyvinyl alcohol in water is sprayed and is visualized using a high-speed camera. The droplet size distribution is studied from simulations with experiments for three spray cases: electrospray, air spray, and air-controlled electrospray. Our simulations and experiments reveal that the electric field is effective in reducing the droplet size, while air flow offers more jet break-ups and thus a larger number of droplets. As a result, air-controlled electrospray where these two driving forces are synergistically combined leads to a larger number of smaller droplets than electrospray or air spray. Finally, we applied three spray processes to obtain a deposition of sulfur/mesoporous carbon/graphene/polymer binder composites as a lithium sulfur battery cathode and demonstrated that air-controlled electrospray leads to a higher capacity and rate capability than other processes, exhibiting 800 mA h g-1 at 0.5C and 600 mA h g-1 at 2C.