Electrophoretic Deposition Sytem Assisted by Rotation

How to Constuct a Lab Scale Electrophoretic Deposition Sytem Assisted by Rotation 

( Raquel Barras)

 

In this post, I will describe how to build a simple automatic rotation system to assist the Electrophoretic Deposition Process when using 1D shaped electrodes. You can download for free, and 3D print the files I've created for this project.

 

Using this system, during the EPD process one of the electrodes will be rotated (the active electrode where the material should be deposited) and the other will be static (counter electrode). To use the static electrode, just cut a piece of hard plastic to serve as support to maintain the counter electrode yarn stretched and still during the deposition.

 

 

 

1. What is Eletrophoretic Deposition

2. Why does it need rotation?

3. How to build the EPD system assisted by rotation

4. Arduino code

5. How to use the system

1. What is Eletrophoretic Deposition

 

Electrophoretic Deposition (EPD) stands as a versatile technique facilitating the deposition of charged particles suspended in a liquid onto conductive surfaces. The process entails the application of a voltage potential across two electrodes. This voltage difference exerts an attractive force on the charged particles, compelling their deposition onto the electrode with the opposite voltage polarity.

 

Key parameters govern the efficacy of this technique, encompassing deposition time, the spatial separation between electrodes, applied potential, particle type and mass, as well as the nature of the electrodes employed. These fundamental factors collectively shape the outcome of the EPD process, influencing the quality and characteristics of the deposited material. A nuanced understanding of these parameters is essential for tailoring the deposition process to specific applications and achieving desired outcomes.

You can learn more about this technique here.

 

2. Why does it need rotation?

 

While exploring conventional electrophoretic deposition (EPD) with 1D shaped electrodes, I noted an intriguing observation – the material deposition displayed asymmetry along the conductive yarn, particularly concentrating at the bottom of the electrode due to the influence of gravity forces.

 

A notable remedy emerged when introducing rotation to the yarn during the EPD process. This rotational adjustment resulted in a remarkable transformation: the material distribution became significantly more homogeneous, covering the entire electrode surface uniformly. This innovative approach not only mitigated the gravitational effects but also demonstrated enhanced control over the deposition process, offering promising prospects for achieving consistent coatings.

 

 

 

 

 

3. How to build the EPD system assisted by rotation

You will need the follwing material:

• 3D printed parts
• metal threaded rod (8 mm)
  
• bolts and nuts as needed
• a wood board (MDF board)
  
• aligator clips with plastic protective head and banana connector (like this)
• 2 plane metallic alligator clips (like this)
  
• 2 metal conductive rods
• NEMA 17 step motor
• rigid shaft coupling
  
• Arduino UNO
• step motor driver
  

 

1. You can start by downloading and printing the machine parts. The part also includes a custom-made container meant to hold the liquid suspension and secure a static yarn electrode (counter electrode) and the one that will be rotated. To secure the counter electrode yarn, just cut a hard sheet of plastic like shown in the picture below and use adhesive tape to hold it at place.

1. 
   
   
2. In the wood board, make perforations using a drill so you can attach the printed parts.
3. Place the nuts inside the geared parts and  use another nut to attach and secure at the right position on the threaded rod.
   
4. Attach the printed parts to the board as shown in the schematic bellow.
   
5. Place the plastic alligator clips on the respective holes and stick the conductive rods inside the banana connector making sure it stays well secured.
6. Use the shaft couple and mount the rod and the stepper motor.
   
7. Connect the stepper motor to the Arduino using a driver.

4. Arduino code

 Use the following code to obtain a roation speed of aproximatly 1 rot/sec.

 

 
#define DIR_PIN 12
#define STEP_PIN 11
#define ENABLE_SM 7


#include <ContinuousStepper.h>


const uint8_t stepPin = 11;
const uint8_t dirPin = 12;

ContinuousStepper stepper(stepPin, dirPin);

void setup() {
  stepper.spin(200);
}

void loop() {
  stepper.loop();
}

 

 

5. How to use the system

You are now prepared to engage the system!

Begin by placing the suspension liquid into the container and attaching both yarn electrodes as demonstrated. Utilize the flat alligator clips to directly apply potential to the metallic rods. Activate the motor by turning it ON.

Now, you have the flexibility to experiment with varying the applied potential and deposition time to achieve the desired type of coating. Enjoy the deposition process, and may your results be precisely tailored to your preferences. Happy experimenting!