If lab equipment can move, then it will never be where you expect it to be…
Which is why, rather than trying to find out where the magnetic stirrer in the lab had disappeared to, I designed my own.
There are many designs for DIY magnetic stirrers online. The fundamentals to a magnetic stirrer are very simple. However, I didn’t want a bodged together stirrer from spare parts. I wanted something that was “right”.
The design principles used to design the magnetic stirrer were:
- It had to be usable in the field or the lab.
- Therefore, it had to be compact and easy to store and transport,
- ……and that includes the magnetic stirrer bars…..
- And it would need to run on batteries,
- Which should be easily replaceable rather than built in.
- As it also had to double as a lab stirrer, it also required power for long term use.
- It had to stir volumes from 10 to 1000 ml.
- It had to be feasible to fabricate.
- It had to be resistant to spills and chemicals.
The final design fulfils all these design criteria.
Cartesian Creations’ magnetic stirrer is a small and compact magnetic stirrer that runs on both AA batteries (rechargeable or alkaline) and USB. On batteries it will run for 40+ hours on a single set of eneloops, while in the lab it can be run from a USB power supply. Using USB as a power source also means the stirrer can be used for long time periods in environments without power such as fridges and glove boxes by using a USB power bank.
It includes a removable drawer for storage of the stirrer bar, and the drawer can be used as a strainer to catch, hold and rinse the stir bar between titrations. The drawer is large enough to hold 3 stir bars up to 30mm.
The stirrer is fabricated from ABS and has similar chemical resistance to a lot of other lab equipment. It can also be fabricated from other plastics such as PETG, PLA if required.
There are no seals or joints in the upper surface. The upper casing wraps around to the baseplate so that any spills onto the stirrer simply drip off the sides. Even if liquid does intrude into the stirrer body, the electronics are mounted above the base of the stirrer and should be unaffected. The drawer storage compartment is sealed from the rest of the stirrer, and includes drains so that the drawer and stir bar can be put away when wet.
The original version of the stirrer is ideal for stirring samples from 10-1000 ml . There are also two variants of the stirrer being developed.
- The first is an even more compact version of the stirrer with a geared motor. This is smaller – around 5 mm shorter in height, and has a lower RPM, and is intended for stirring of very small samples up to around 500 ml, especially for groups doing remote fieldwork.
- The second is an XL stirrer, designed specifically for stirring 70-80 mm stir bars. It is bigger in width and depth to provide a larger base for larger samples. It has a lower RPM, and massive magnets. It is specifically designed for stirring large samples and will not work with smaller 25mm stirr bars.
If you would like a magnetic stirrer, please contact me, or visit my my Etsy store:
I have also made the design available under a Creative Commons – Attribution – Non-Commercial – No Derivatives license, here: . However, be aware that it is a challenging print, and you will need to have your 3D printer very well dialled in. It is also not the most up to date variant of the design.