 Hi, my name is Braden Ring-Eisen and I'm head of the bioenergy and biofabrication section here at the Naval Research Laboratory in Washington, D.C. I'd like to talk to you briefly about our recently published manuscript titled PLGA Hydrogel Biopapers as a Stackable Substrate for Printing Huevec Networks via BiOLP. Cells can now be printed by several different methods including retooling jet printers, micro pens, electrospray nozzles, as well as laser guidance and laser forward transfer approaches. BiOLP is an example of this ladder technique where laser pulses are used to propel droplets of cells onto a receiving substrate. In the past, we've shown that BiOLP can form 3D cell constructs by alternating between printing droplets of cells and spreading layers of hydrogel. This approach, however, is a little limited because hydrogels are the only material that could be layered in this way and any cell differentiation has to occur after the entire construct is built. Ultimately, a greater diversity of materials is required for most tissue engineering applications and researchers would prefer to have more control over the timing and type of cell differentiation. Our manuscript is the first to describe research that demonstrates the use of thin biodegradable polymer sheets as viable substrates for cell printing. We believe that biopapers like these will facilitate tissue and organ printing from the bottom up by creating pre-vascularized constructs layer by layer. Our biopapers have a maximum pore size of about 300 microns and are mechanically stable enough to be loaded into a cell printer, sort of analogous to regular paper being loaded into your desktop printer. They can also support cell growth and differentiation when infused with matrogel, yet retain enough stability to be stacked into multi-layer constructs after printing and cell differentiation has occurred. To demonstrate the biopapers' printability, we used BiOLP to form micron-scale branched patterns of humanabilical vein into thiel cells onto individual matrogel-infused sheets. We observed tubulogenesis of the printed HUEVAC cells as they grew together to form cord-like networks that actually followed the printed design. Next, my colleague Kurt Pirlo will show you how BiOLP is used to create live cell patterns on stackable biopaper substrates. So after we bring the papers off the ice out of the refrigerator and put them in the incubator for five minutes so that the rate of cells in the matrogel has gel. This is the ribbon that we'll put the cell ink on. First, we load the paper onto the bottom translational stage. It is right here. This is an XY-stage micropipette. The cell suspensions slide into this mount which is connected to the top set of XY-stages. And make sure that the distance between the paper and the printing ribbon is about a millimeter. And we make sure that we have ribbon to print from or onto the paper. Immediately after printing we add some media to keep the paper from dehydrating, but don't yet submerge the paper because the cells are still attaching and we don't want to wash them away. We just add a little bit of media around outside. Put it back in the incubator for five minutes. That's the whole process and then you repeat that.