1. 3D Bioprinter Detailed Design
Nicole Mazzola, Matt Williams, Reed Truax, Matt Freyman, Aaron Gaylord, Taylor Fowler, Moises Gomez

2. Agenda Detail Design MSDII plans Head Movement Nozzle Design
Bed Design
MSDII plans

3. Head Movement
Taylor, Matt F

5. Changes Made Updated Marlin to Accept Motherboard (MKS-Gen-L)
Invert Endstop Flags
Disable Bed Temperature
Set ‘Dummy’ Nozzle Temperature Reading

6. Attempted Changes Update Marlin from v1.1.2 to v1.1.9
Attempted to add pinout from motherboard and get additional features
Created UI and Motor Stability Issues
Remove Requirement for Temperatures Entirely
Attempted to remove errors for low temperature errors
Overly large time investment compared to dummy thermistor reading

7. Defining Movement Settings
All the motors have 1.8° stepping meaning 200 full steps per revolution, however microstepping can be implemented to reduce the distance of a step well into the sub-mm range. The distance per step used in testing was 10µm, as calculated below.
Idler Teeth - Number of steps on the idler interfacing the motor to the belt
Belt Pitch - Distance between the teeth of the belt.

8. Results of Movement Testing
50 Steps of 10µm (500µm): Steps of 10µm (100µm):

9. Summary of Movement Results:
Axis of Movement
Average 500µm Step, Changing Directions (µm)
Average 500µm Step (µm)
Average 100µm Step (µm)
100µm Adjusted to 500µm (µm)
Comparison of 5x100µm Steps to 500µm Step (%) X
292.1
494.1
88.9
444.5
89.96 Y
60.96
465.7
84.67
423.35
90.9
Movement along X axis is closer to theoretical values with easier transition between directions than movement along the Y axis because of different construction, loose belt, or misalignment of belt and pulleys.
The solution to issues in changing directions and others emerging as the number of steps is reduced includes: tightening the belt, and improve proper belt alignment, consider purchasing a better belt and/or idlers which would sit better.

10. Nozzle Design
Reed, Matt W, Aaron

11. Method of Nozzle Assembly
Sandwich of acrylic, tape and shim stock
Allows the height of the channel to be easily controlled

12. First Prototype

13. Nozzle Design

14. Solenoids Previously considering $140 solenoids
Found $50 ones from ASCO
Looking at 3 way and 2 way valves

15. Solenoid Types

16. Reservoirs Will consist of: 250 ml Glass beaker
Cap with holes for inlet/outlet
+/- 15 psi pressure sensor
Solenoid
Controller (will explain)

17. Air Supply Using lab air instead of a compressor Cheaper
Less complex to build
Don’t need a pressurized tank
Don’t have to worry about sizing a pump

18. Pressure Controllers One Arduino Tiny per reservoir
One Arduino Mega for all reservoirs

19. Pressure Controller Pros/Cons
One Arduino per Reservoir
Pros:
Computationally faster
Easier to prototype
Easier to build
Cons:
Harder to integrate (each tiny needs to be updated)
One Mega Controlling all the Reservoirs
Pros:
Easier to update
One screen
‘Tanks know what other tanks are’
Cons:
Limited number of reservoirs
Computationally slower (can't react as fast)

20. Plans for next phase Test both solenoid types
Prototype the two controllers/debug
Order parts for reservoirs and air supply
Begin assembly (time permitting)
Iterate on nozzle design
Begin testing nozzle with pressure system

21. Bed Subsystem
Nicole, Moises

22. Updates on Viscosity Remeasurements
We met with Dr. Day on 12/4 to remeasure the 1% and 2% Sodium Alginate Solutions, as well as a 1% Sodium Alginate solution containing 10% and 20% dextran.
Table 1: New viscosity measurements using load cell and torque.

23. Other Sodium Alginate Details
Information from the Product Sheet
The Molecular Weight is g/mol
According to the product info sheet, sodium alginate is about cP for a 1% solution in dH2O
We plan to use a 1% Sodium Alginate Solution for printing
Commonly used for printing in literature for biological applications.

24. Design for the Bed Magnetic particle idea on hold because of $$,
We have chosen a bed design with a porous bed
It will remove excess fluid from the nozzle while catching the alginate strands
Stainless steel mesh for the porous material
Opening diameters smaller than the diameter of the alginate strands
We ordered sample mesh pieces from McMaster Carr to test out various opening sizes for the mesh.

25. Design 1: Without Sponge
Figure 1: Bed Design Model exploded view, without sponge in basin. There is a wire mesh with a frame and a basin underneath to catch excess fluid.

26. Design 2: With Sponge
Figure 2: Bed Design model exploded view with sponge in basin. There is a sponge in the basin that rests against the wire mess so that excess fluid can be absorbed. Left is exploded view, Right is put together.

27. Plans for next phase
Create a 3D printed model utilizing sample meshes from McMaster Carr
Run preliminary tests to see if the fluid and alginate catching works
Test to see if dextran helps with adhesion
Order proper size mesh
Machine metal parts for the final design
Attach bed parts to printer