A Hacked 3D Printer Towards the Printing of Materials through Biological Organisms

Over the last couple of years, 3D printing technology has received a lot of attention and this is not a surprise as the technology has an unlimited number of applications from a materials perspective. Addictive manufacturing surpasses subtractive manufacturing, as printing of intricate structures is now possible with a simple 3D CAD model. With this project, we are seeking to print 3D composite materials with multifunctional capabilities using synthetic gene networks to drive the printing process via encoding the materials to print at the DNA level in microbial organisms. To do the printing part, we modified a commercially available 3D printer, the MakerBot Replicator 2X. We first modified the printer’s extruder head to be able to print a blend of agarose and cells from two individual reservoirs instead of the routinely used ABS or PLA plastics reel from a spool. Using an optical interrupter, we detect when the piston in the slider-crank configuration is moving up and fill in the chamber with the agarose and cells blend that eventually carves into the structures. A solenoid valve, normally closed, controls the agarose input and a DC liquid pump (and a second solenoid) controls the cell input via an Arduino microcontroller. When the piston is retracting (moving up), we applied a long enough time delay on the solenoid and the DC liquid pump to compensate for the lost in pressure in the mixing chamber. In addition, a set of check valves prevents the flow of these liquids back to their respective reservoirs. The piston displaces the agarose and cell blend through the nozzle as it is moving down. This design permits us to use an established skeinforge gcode generator with minor tweaks. In this case the sensing of the piston position occurs concomitantly with the machine-inherited 3D printing process. For the agarose feeding system, we have a hermetically seal chamber with one inlet for air and one outlet for the agarose to reach the printing head. To maintain the agarose in the molten state (upon exposing the agarose to 60°C ) a magnet wire is wound around the tubing. The house air fills the chamber and because of the built-up pressure the agarose is propelled to this printing head. The agarose needs to be able to support itself without distortion as the patterned filaments are printed. Using a rheometer, we characterized the gelation time, the melting temperature and the shear thinning properties of this agarose. From a synthetic biology perspective, we are developing a broad host CRISPRi system (based on light sensing and recombinases tools) to control the production of cellulose in Gluconacetobacter xylinus during the printing process as the cells are exposed to ambient light.