# Week 14: Wildcard Week - Bioprinting with Filippos <a href="../index.html">Back to Home</a> This week I worked with Filippos to do 3D printing with green fluorescent protein (GFP)-expressing E. coli cells embedded in a pluronic gel. The cells glow green when excited by blue light. Pluronic is used because it's a liquid at 4 degrees C, allowing for mixing with bacterial culture when it's first taken out of the fridge; it then solidifies into a gel after about 5 min upon reaching room temperature. The first day we just tried to pipette a design with the fluorescent cells mixed with 20% pluronic: <img src="images/leaf.jpg"/> (The image was taken with an E-Gel Imager, with the fluorescence colored green in ImageJ). It was not very viscous and didn't hold its structure when the plate was tilted. The next day we used Filippos' customized printer and a customized printer program (Simplify3D) to print a 3D structure with just the pluronic, using 40% pluronic this time, which does keep its structure once printed. The tip of the syringe used to hold the material is 260 microns in diameter. The key was to optimize the extrusion multiplier (rate of extrusion), printing speed, and layer height (how high should the extrusion tip be raised after printing each layer) parameters. The structure I chose to print was a dome. We used a rectilinear infill at 20%. (STL file <a href="dome_bioprint.stl">here</a>) <img src="images/gcode.jpg"/> At first we tried extrusion multiplier at 0.1, printing speed at 200mm/min, and 0.5mm primary layer height. This resulted in a decently good print, but there was too much material extruded at once and not enough height, which made the lines squish into each other a little. We changed it to 0.09 extrusion multiplier and decreased the first layer height to 80%, which made a pretty beautiful print: <img src="images/pluronic_dome.jpg"/> Filippos then printed it with the cells mixed in: <img src="images/fluorescent_dome.jpg"/>