Multi-Material Bioprint Design Guide

Several Allevi platforms have multiple extruders which means you can bioprint a multi-material construct. Below, we discuss the process of designing your bioprint to make the most of this feature.

Multi-Material Bioprint

Separate Single Material Constructs

First, let’s say you would like to compare two materials, Material A (Blue) and Material B (Red). Your first test is bioprinting a cylinder out of each material side-by-side in the same petri dish. Let’s also say that you’ve done some parameter optimization for each, and you know good print parameters for them independently.

Design

  • First, create (or download from the Allevi Files tab of the Current Print window) a cylinder STL file. Make sure its dimensions would fit in the side-by-side configuration, and that it would not require too much material.
  • Next, upload that cylinder STL file into the Allevi Software to design Cylinder A, the cylinder composed of Material A.
    • Assign the file to Extruder 1 which contains Material A in our example.
    • Choose the print speed and layer height you want for Material A. Also, select an appropriate infill geometry for your comparison. For more on the infill options available in the Allevi Software, you can review our Infill Options guide.
    • Make sure that you program an offset to leave room for the other cylinder. Let’s say in this case you would program an X-offset of -10 mm to move Cylinder A 10 mm to the left.
  • Now you can design Cylinder B, your cylinder made of Material B.
    • Upload the cylinder STL file again and this time assign it to Extruder 2.
    • Choose the print speed and layer height settings you want for Material B. Then, select an appropriate infill geometry for your comparison.
    • Apply a similar offset for this second cylinder. Let’s say an X-offset of +10 mm to move Cylinder B 10 mm to the right.
  • Your design is ready to print!

How It Prints

In this case, your cylinders won’t be overlapping and each will print layer-by-layer. That is to say, the first level of Cylinder A will print, then the printer will switch extruders, then the first layer of Cylinder B will print. The printer will switch back and forth in this way, building both cylinders from the bottom up. This way, Extruder 2 won’t squish the top of the Cylinder A while printing the bottom of Cylinder B.

Single Multi-material Construct with Basic Interface

Now, let’s say you’d like to design a multi-material construct to illustrate a flat material interface between Material A (Blue) and Material B (Red). You can make one section of Material A layers and one section of Material B layers on top.

Design

  • First, create a short box shape STL. This will represent several layers of the given material which we will call a slab. Make sure it fits in the petri dish in the X/Y Plane.
  • Next upload the slab STL into the Allevi Software to design Slab A, composed of Material A.
    • Assign the file to Extruder 1 which contains Material A.
    • Choose the print speed and layer height you want for Material A.
    • Then, select an appropriate infill geometry for your interface. Note that there is not a shell (structural wall) along the top of the slab. Therefore, the infill geometries of the two sections will form most of the interface.
  • Next, upload the slab STL again to design Slab B, composed of Material B.
    • Assign the file to Extruder 2 which contains Material B.
    • Choose the print speed and layer height you want for Slab B.
    • Similarly, select an appropriate infill geometry for your interface.
    • Now, apply a Z-offset to ensure that the Slab B prints on top of the Slab A. Let’s say that our slabs are both 7 mm thick. Therefore, you would apply a +7 mm Z-offset to Slab B.
  • Your design is ready to print!

How It Prints

In this case, Slab A will print layer-by-layer. Then, the printer will switch extruders and print Slab B layer-by-layer directly on top of Slab A.

Single Multi-material Construct with Complex Interface

Maybe your multi-material construct needs to demonstrate a more complex interface than flat layers. You can design two sections, each with their own side of the complex surface.

Multi-Material Bioprint

Design

  • First you should design the distinct portions of your construct.
    • The base of this construct, which we will call Component A (Blue), has a rectangular bottom, straight sides, and the complex interface as its top. You want to design the depressions in Component A (Red) to make room for the protrusions of Component B. You can do this through several different techniques. Note that you need to account for every part of the interface you want to be made of Material A when designing the top of Component A.
    • The upper component, Component B, has a rectangular top, straight sides, and the complex interface as its base. Similarly to Component A, you should design all of the protrusions you want to be made of Material B in this STL.
  • With your STL files made, you can start arranging your print. First, setup Component A.
    • Load the Component A STL file.
    • Assign Component A to Extruder 1. Adjust the print speed and layer height settings according to your optimization for Material A.
  • With the base of the construct set, move on to setting up Component B.
    • Now load the Component B STL file.
    • Assign Component B to Extruder 2 and adjust the print settings accordingly.
    • Now you can apply a Z-offset to Component B. You want the protrusions in Component B to rest exactly in the recesses of Component A. Let’s say you’ve determined that the longest protrusion in Component B will contact the bottom of the associated recess in Component A with a +7 mm Z-offset. Apply that +7 mm Z-offset to Component B.
  • Now your construct is ready to print!

How It Prints

In this construct, most of Component A will print layer-by-layer until the print reaches the interface. Consider the first layer that includes a cross-section of Component B. The printer will print everything in the same layer height before lowering the bedplate for the next layer. Therefore it will continue using extruder 1 to print all the portions of Component A in that layer. Then it will switch to Extruder 2 and print the portions of Component B in the layer. After that, it will lower the bedplate, switch back to Extruder 1, and print the portions of Component A in the next layer, and so on.

Single Multi-material Construct with Alternating Layers

Now let’s say you want to model a complex multi-material system with alternating layers of Material A and Material B. Let’s also say you want to put Material B on the bottom of this construct, and Material A on the top. You can design the alternating layers of each material and combine them into a single construct.

Multi-Material Bioprint schematic

Design

  • First, design of the layers of Material B and Material A.
    • In this example the layers will be very similar to our slabs from the second example above. You do, however, want them to be vertically shorter since there will effectively be 4 slabs in the final construct.
    • Create an STL file with two slabs. One can be resting on the build surface. The second slab should be hovering over the first. It should be centered over the first in the X/Y Plane as well. The gap between the two slabs should be the size of a third slab. This STL will work for both materials.
  • With the STL designed, you can upload your file into the Allevi Software.
    • First, upload the Layers STL and assign it to Extruder 2 this time. This will be the Material B Layers piece.
    • Make the appropriate parameter selections for Material B.
    • Now, upload the Layers STL again and assign it to Extruder 1. This will be the Material A Layers piece.
    • Make the appropriate parameter selections for Material A.
    • Now, apply a Z-offset to the Material A Layers STL. The slab sized gaps you designed into the STL’s means that the parts should fit together perfectly when you apply a Z-offset equal to the height of the slabs. Let’s say that height is 5 mm. Use a +5 mm Z-offset on the Material A Layers to shift them up.
  • Now your construct is ready to print!

How It Prints

The printer will handle this construct in a very similar way to the Single Multi-material Construct with Simple Interface above. However, since Material B is on the bottom, the print will begin with Extruder 2. It will eventually switch to Extruder 1 for the first Material A Layer, and so on.

Other Constructs

Most other constructs can be achieved using the principles from the examples above. The most important thing to remember is the bottom-up, layerwise deposition method of the printer. If you have any questions about a specific print you want to try, feel free to contact the Allevi Support Team.

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