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

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

Head Movement Taylor, Matt F

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

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

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.

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

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.

Nozzle Design Reed, Matt W, Aaron

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

First Prototype

Nozzle Design

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

Solenoid Types

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

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

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

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)

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

Bed Subsystem Nicole, Moises

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.

Other Sodium Alginate Details Information from the Product Sheet The Molecular Weight is 216.12 g/mol According to the product info sheet, sodium alginate is about 15-25 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.

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.

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.

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.

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