Tubing and connectors
Also known as plumbing
For reference: Inner diameter = ID, Outer diameter = OD. Quotation marks (") indicate inches, single apostrophe (') indicates feet. Most eVOLVER hardware is in US customary units (i.e. not metric) due to wider availability of parts.
Standard components
Tubing
The standard eVOLVER package includes 1/16" ID (1/8" OD) soft silicone tubing for all fluid handling operations. For exact specifications, see the part sourcing google sheet, "Fluidics" tab.
Silicone is the tubing of choice for eVOLVER because of its flexibility, durability, cost, and resistance to beach and ethanol. It is also autoclavable, although 30 minutes of 10% bleach sterilization is sufficient to completely sterilize the lines.
Silicone tubing is highly permeable to gasses, including water vapor. If you leave media in the tubing for >1 week, it will likely dry out and cause an obstruction (see obstruction troubleshooting).
Connectors
The standard eVOLVER package includes 1/16" barb to luer-lok connectors for all pump-to-vial connections. For exact specifications, see the part sourcing google sheet, "Fluidics" tab.
The barb side of the connector is rated for the ID of tubing it is mean to be used with, i.e. 1/16" barb for 1/16" ID tubing, 1/8" barb for 1/8" ID tubing, etc. Barbs are designed to get a tight seal around their widest diameter, with the max pressure and resistance to slippage depending on the softness of the tubing and style of barb (40 psi for standard eVOLVER connectors).
Luer connectors work by pressing a "male" plug into a "female" socket, both tapered at 6%. Because of the smooth surfaces and large contact area, this creates an effective seal without tools, held in place by friction. Syringes and medical equipment commonly make use of luer connections.
To hold luer connections in place more securely, luer-lok connectors use a screw-like "skirt" to prevent luer connectors from simply being pulled apart. eVOLVER tubing connections are luer-lok, allowing for easy but relatively secure connections between most components.
However, luer-lok connections have some common failure modes. Because the threads of the skirt are so coarse, it only takes a 1/4 turn to break the seal at the plug-socket interface, leading to a leak (if positive pressure) or air bubble source (if negative pressure). Loose luer connections easily become disconnected, leading to spills (the major source of electronics failure) and of course, failed experiments. One should always ensure luer connections are snug (hand tight), and tubing free from torsion that might unscrew the luer-lok.
Additionally, because the male connector comes in direct contact with fluid, it becomes your most likely contamination source. Be careful not to bump the tips of the male connectors against contaminated surfaces when setting up your experiment. Doing a final wash with 70% ethanol after bleach sterilizing can prevent some contamination from this route, depending on your media and organism.
For more information on luer connections (and credit for the above images), see here: https://www.apsf.org/article/managing-luer-connections/
Swapping and modifying
Any soft tubing (durometer 40-70A) works well with the barbed connectors. Vinyl (PVC) or tygon tubing might be a suitable alternative for decreased permeability. Opaque tubing may make sense for light-sensitive media or antibiotic feeds that have extended time exposed to light in the tubing due to low flow rates, at the cost of not being able to observe media in your line. Remember that 1/16" ID tubing contains about 0.75 mL per foot.
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