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I. INTRO

The bio-printer functions similar to an ordinary 3axi 3d-printer, which has extrution speed and nozzle x,y,z moving control. The moving control is operated by three motors at its x plane, y plane and z plane. The printer reads gcode file in order to locate nozel location with only 0 and 1 serial data. The bio-printer we used is a customized Direct Writing Microextrusion with carefully optimized parameters of extrusion rate, transitional stage speed for the ink's rheological properties.

II. PROCESS

1. Preparing the gel as bioink

The first day of the lab we did preparation and optimization for printing gel using thermoresponsive gel called Pluronic. Pluronic will become liquid if the temprature is low enough. We mixed and tested different propotion of Pluronic and water to optimize its rheological properties. If the gel is too liquidy, the printing layer will merge together and colapse while if it is too solid the layer wont have enough shear force and friction to stick itself. We tested the gel using needle and prepared 1:3 as a good formula setting.

2. Load the gel to printing needle

We carefully removed the plastic cap from the printing nozzle needle and loaded the gel from fridge while it is still in liquid property.

Pouring the gel from the back

Squeeze out extra air

Turn from the top side

Set for 15 min for the gel to become firmer

3. Design the print

Rhino is used to prototype a easy circular pattern file. The file is exported into stl file and send to the printer to slicing and converted to g-code.

4. Printing

The printing is quite successful with 1:3 bioink we prepared. However, when it reaches to third layer, the gel started to shift.

The reason is because the layer height currently is set to 2 mm and is probably equal or larger than the diameter of gel extruded from nozzle. Another reason can be the weight of several layer gels constantly add to the pressure for minimal yield force.

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