Given our motivation to have the sonification setup resemble a record player, it made sense to design the petri dish in the form factor of a traditional vinyl record. The standard types of vinyl records include Long Play Vinyl Records (LPs), Singles and Extended Play Vinyl Records (EPs), and Standard Play Records (78s). The standard diameters sizes are 12 inches, which typically play at a speed of 33 ⅓ rotations per minute, and and 7 inch records, which are commonly played at 45 rotations per minute. It was decided to make both sizes in order to experiment with different surface area distributions and to plate a variety of teammates while being economic about material usage. The 7” record standard was kept, but the standard 12” record was scaled to the footprint of the Audio Technica record player that was hacked for this project. A typical LP hangs over the edge of the bed of the record player, but because of the uncertainty of the weight and stability of our petri record, the record was scaled to 10.47” in diameter (the exact size of the bed of the player with no overhang).
Team:EMW Street Bio/Hardware/Records
Microbiome records
Design Considerations
Distribution of Bodily Sites
A big design consideration was how to distribute the sites of different body parts across the plate- concentrically, from the center outwards, or consecutively, linearly as it rotates around. (See image below.) The concentric design has the benefit of a stronger resemblance to the iconic look of a traditional record and maintains the sonification of one body area over a longer period of time; one track is one body site. The consecutive model has the advantage of rapidly juxtaposing the different body sites over time, so one might discern the differences more distinctly. Both were produced for testing.
Fabrication
It was decided early on to construct our petri records out of acrylic due to its availability and watertightness. Records were produced with laser cutting for ease of access and speed of fabrication. The design for the record was modeled in a 3D CAD tool, Rhinoceros, and then laser cut.
One of the design constraints was the size of the material and our laser bed versus the size of the record. To build the walls of our petri dishes up, circular walls were stacked and glued. This resulted in a lot of wasted material (the center being discardable material). To be more economical, the walls were split in halves for more compact nesting on the sheet. The tradeoff to this was more labor.
Image of the laser file:
The green lines are cut lines, red lines are for etching for alignment and registration purposes, and the black lines are purely references for lid versus bottom and acrylic sheet size, not to be cut.
Assembly (October 1st)
After the file was cut on the laser bed, the protective paper was peeled and the parts were assembled along the etch lines of the base. A sparing amount of acrylic glue was applied with a syringe then pressure was applied until the acrylic bond set.
Finished products:
Things we learned in the process
- Lids need to be smaller and as close as possible to the size of the bottoms
- Use pipettes to "pour" agar and reduce contamination while creating standardization
- Try adding small notches (5 or 10, around each of the radial plate design's ends) to be glued on the inside of the lid to prevent slipping of the lid and reduce contamination
- Increase 1/4 inch dividers by an 1/8 inch
- Possibly increase the height of the dishes
Fabrication files are available here
