Syringe Pump Extruder for 3D Bioprinting
Project Description
Design and build a piece of open hardware for engineering biology. For the duration of the class, you will need various tools to execute the experimental homework. Build at least one piece of open hardware for your lab.
The chosen project area is bio-printing. In class, we have learned about ways to work with biological materials to create structures. From inkjets to larger deposition systems, hardware is critical for precisely spatially orienting bio-materials. Therefore, I decided to build a syringe pump extruder.
Design Requirements
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The object should be multi-functional: 1) attachable to a regular 3D printer and 2) self-supportive, in case a biolab doesn't have access to a 3D printer
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It should be easy and fast to replace syringes in a non-destructive way
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The position of the syringe should be adjustable in the z-axis
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The stepper motor should fit on top
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The construction has to be stable and able to resist mechanical torsion created by the stepper motor
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The object should span at least the diameter of a petri dish
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The object should be attached to wheels, for manual movement in the xy-axes
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Optional: a possibility to use multiple diameters of syringes
MATERIALS and tools
Tools
- Ultimaker 3
- Laser cutter
- Screwdrivers
- Round burnisher scraper
- Tap and T-wrench
- Wire cutter
Software
- Solidworks
- Adobe Illustrator
- CorelDraw
- Arduino
Hardware
- 1x M8x1.25 Rod (120mm long)
- 1x M8 hex Nut
- 4x M6 25mm bolt
- 2x M6 hex nut
- 4x mini bolt and nut
- 1/4' acrylic sheet
- 4 x caster
- 4x rip-tie
Biology
- 50 ml syringe pump
- Petri dish standard size 3-1/2” x 5/8”
Electronics
- 5V stepper motor type 28BYJ-48
- Arduino Uno
- L293D IC dual motor driver
- Half-size breadboard
- Jumper wire pack
- 9V Battery
lab notebook
1. First, I 3D printed this simple paste extruder downloaded from Thingiverse.
Lessons:
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Space between largest gear and its holder is too big: the wheel wiggles
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The hole for the M8 was not big enough, probably because of the tolerances of the 3D printer (20% infil)
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Scraped out the hole, then there was too much space, so the screw didn't rotate with the gear
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The object is bulky and tips over, because the center of gravity is off
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There is no support for the syringe pump holder and it also cannot be attached to a 3D printer. Support is needed to make it stand upright, otherwise the syringe falls out of the holder.
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There was only an M8 screw in the makerspace, not a rod. This is problematic because the screw hits the syringe holder.
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It is not explained how the rod is attached to the syringe. If you glue it, you can only use the syringe once.
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The code for the arduino/stepper motor was not detectable
2. Next, I 3D printed this stepper motor-based paste extruder which is a remix from the simple paste extruder in step 1. This version is specifically designed for a Delta 3D printer.
Lessons:
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The overall design is much better
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Still had to widen out the hole for the M8 with a round burnisher scraper, this time it was done precisely correct
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The holes in the small gears are round instead of oval, thus not adjusted to the size of the stepper motor. This makes it difficult to stick the stepper motor in the 3D printed part.
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Instead of an 80 mm M8 bolt, I used a 120 cm M8 rod to allow the syringe pump to discharge completely, instead of halfway.
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The holes for the stepper motor aren't in the right position, because this Maker used a larger stepper motor
first prototypes
3. Because I still had no code, I looked for examples in other places and found a 3D printed syringe pump on Metafluidics
Lessons:
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In this model, there are no gears needed to make the syringe pump move, the entire system is in one plane. This seems great.
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Downloaded the 3D modeling software OpenSCAD
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The code is made available and seems usable. But this project uses a different type of motor, so I'm not sure if the code is still usable with the 5 stepper motor I bought.
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It is a great idea to 3D print a holder for the upper part of the syringe pump, to slide it in and lock it. I'll make one of those.
4. Design of the syringe pump slider/holder
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First, a simple model was made with foamboard
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Because the OpenSCAD software seemed difficult, I designed the part in SolidWorks
electronics
5. I followed the Adafruit instructions to make the electronic circuit.
Lessons:
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The circuit board was successful, but the code didn't work. I tweaked some of the parameters, but it kept on giving errors.
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In the Arduino database with examples, I tried various programs and they all worked.
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In the Stepper_oneRevolution example by Tom Igoe, it initiated the stepper library from pin 8 through 11. I changed this from 9 to 13. Then it worked.
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Next, I deleted the counterclockwise serial loop because I want the motor to go in one direction.
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The delay was set to zero, because I want a continuous revolution without breaks in between.
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Raised the speed to 100 rpm.
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Once the code is uploaded on the arduino, it can run without a computer when a battery is attached to the Vin and GND.
Breadboard layout
The layout is based on the tutorial from Adafruit.
Arduino code
The code was adapted from an example in the Arduino library.
#include <Stepper.h>
const int stepsPerRevolution = 50; // change this to fit the number of steps per revolution
// for the motor
// initialize the stepper library on pins 8 through 11:
Stepper myStepper(stepsPerRevolution, 9, 10, 11, 12, 13);
void setup() {
// set the speed in rpm:
myStepper.setSpeed(100);
// initialize the serial port:
Serial.begin(9600);
}
void loop() {
// step one revolution in one direction:
Serial.println("counterclockwise");
myStepper.step(-stepsPerRevolution);
delay(0);
}
All Videos
6. Finally, the last step was to bring everything together.
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I designed 'legs' for the structure in Illustrator and used a laser cutter to make it
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Unfortunately, the only available acrylic sheet had a width of 10 cm. This means that the structure cannot span a petri dish.
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The height of the syringe is adjustable, rip ties are used to lock the 'legs' in the desired postion
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Because my 5 stepper motor is smaller than the motor that was used for the syringe pump extruder 3D model, it didn't fit on the structure.
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This was resolved by laser cutting an acrylic part for the small gear
IT WORKS!!
Further improvements can be made in the following areas:
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redesign the 'legs' to create a wider span
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bend the acrylic 90 degrees to connect it to the wheels
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use a larger stepper motor
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redesign the entire syringe holder to get rid of the unnecessary perforations
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3D print the block again with 'high infill' settings to make the piece finer and with higher density
