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FINAL PROJECT

Tube Capping/Decapping Module

Motivation: To achieve high-throughput organic synthesis, liquid moving is frequently required. Our lab has a Tecan Freedom Evo platform with liquid pipetting and robotic arm moving utilities to automate the processes. However, it has a pick and place arm to rotate tubes but doesn't come with a part to hold them. Currently we have to decap all tubes manually before moving liquid, which impedes the automation of the processes. Thus, for the final prject, I plan to make a tube capping decapping module for the robotic experimental platform in our lab. One example is here: Novartis example.

The basic plan is to use a lathe chuck structure to fix a tube, driven by a motor, and controled from terminal so that I can integrate the commands in Python scripts. Can see this video for a closer look of the mechanical. The basic plan is to purchase a lathe chuck as a basis, and 3D printed jaws to fit the size. However, I found after adding some foam, the jaws can hold the tube tightly and provide extra resistance to avoid slipping, so I went with that.

To use a motor to actuate the rotatory motion, I planned to design the gear myself. But I found it's difficult to design a gear fits well with the rail, so I deisgned a joint to connect a motor and the gear instead. Also, to fix the lathe chuck on our platform, I 3D printed a mount for it. And they work. Then I designed a motor mount. I found the geared DC motor I am using is a Kysan 38GM series, and is a typical 37 mm motor. I found some design examples for the motor and the mount from STLFinder, and modified it so that it can be fixed on our platform.

To close the loop of control, I wanted to use a step response to sense the distance between jaws as a feedback to contorl the motor. The signal is pretty clear, though it only appears when things contact. How to improve the control algorithm with that signal is still to be explored.

For the electric contorling, my original plan was to use ESP32 to achieve wireless control via WiFi. I adopted the board deisgn from this as a basis and added the motor driver on it. I designed the board with SVG-PCB, milled and soldered it, but it doesn't work consistently. I just worked once after resetting about 20 times, and gets stuck while connecting to WiFi in the remaining cases. Quentin told me it's probably the soldering issue, but I failed to debug it and decided to use SAMD11C with a USB wired contorl instead.

Future plan: Though wireless control is not necessary, it would be nice and save wires. So I will explroe a connection using a ESP32 dev board. I am currently using 5V from USB as the power source, but the geared DC motor could use 12V power. To accelerate the speed, I plan to change the poewr source.

Achknowledgement: Thanks Miana and Quentin for the help during this project!