Bioreactor print Bed: Imaging and Lighting

(under construction)

KSU Graduate research: Part 1.5

Working as a Graduate Research Assistant for Dr. Razvan Voicu I was tasked with two research objectives. The first of these was to take an existing 3D printer and modify it for our purposes. The 3D Bioprinter works in conjunction with an optically enabled print bed that I designed. The print bed includes an HD camera and a unique lighting system. The second was to create a specialized bioreactor, but I that information cannot be shared yet, due to a non-disclosure agreement.

This page covers the work on this imaging and lighting system.

Objective

The idea behind this work was that we wanted to be able to monitor biological 3D prints during and after the printing process. This ability would enable us to track cell placement and growth and potentially intervene, if needed.

PRocess

Design Requirements

This system had to be designed around the Raspberry Pi and the camera. It also needed to be cylindrical due to certain specifications outside the scope of this page. An adequate lighting system was also required to properly illuminate the print area.

HArdware Selection

We knew that we wanted to be able to view and record live video and capture still images. We also knew that we wanted to be able to control things like lights and zoom. Making sure that we could add more features in the future was also important.

Because of its memory size, processing speed, and plentiful outputs and inputs, we decided to use the Raspberry Pi 5.

For the camera, we went with the Arducam 12.3MP IMX477 IR-CUT Camera Module. The 6mm lens was perfect for viewing very close targets at high detail. The adjustability was also a major factor. It easily connects to the Raspberry Pi.

For the lighting system, we knew that we wanted a bright, white, diffuse light. The Raspberry Pi output was restricted to no more than 5V and 2A.

This LED light strip matched all of those requirements and was also inexpensive.

Base design

The first part of the design work was to create a base to house the Raspberry Pi and the camera.

I designed the enclosure to fit the Pi, while also making sure that there was enough room for the required connections and that it the ports and jacks were accessible from the outside.

I also had to make sure that the camera focus could be adjusted. To solve this problem, I designed a belt that would match the grip grooves on the barrel of the camera lens. To turn the belt, I created a pully on an adjustable mount. The outside of the belt was printed with a rough texture for grip. To adjust the camera focus, all one needed to do is turn the pully and belt from the outside, as seen in this video.

The upper part of the device needed to allow enough space between the lens and the print bed and provide housing for the lighting.

Lighting Design

The lighting needed to illuminate the print surface obliquely and be as diffuse as possible to minimize glare. To achieve this, the lights were recessed into the body of the device, under a laser cut diffuser, and reflected onto the underside of the print surface with a white 3D printed ring reflector.

In addition to those measures, the conical surface between the camera and the build plate was painted with Black 3.0. This has a very low albedo and was extremely effective in reducing visual reflection.

Software and Results

To control the camera and the light through the Raspberry Pi, I need a program with a GUI. I started off by using the Picamera2 python software. This includes many controls and options.

I modified it to handle up to 17x zoom and toggle the light on and off with a button.

The results were exceptional. The images were clear and sharp, with excellent magnification.
The picture to the left shows the lab through a droplet of colored collogen.
The photo of the transistor is another good illustration of the magnification.
The other picture and the video show a successful test print. using petroleum jelly and colored collogen.

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