Magnetic stirrers are often used in labs for buffer solutions, protein dialysis and other biology or chemistry experiments that require constant stirring for long periods of time. This type of stirrer is often used because it limits the risk of contaminating the chemicals and liquids being tested. It also prevents settling and allows for hands-free stirring for experiments that require a homogenous mixture.

Some professional magnetic stirrers can be expensive, and if you are using one at home, it can be cost-effective to make your own. There are various versions of do-it-yourself magnetic stirrers, but here is one way to build a cost-efficient stirring alternative.

How a Magnetic Stirrer Works

Magnetic stirrers use an applied magnetic field to enable hands-free stirring. This magnetic field rotates and causes the magnetic stir bar in the liquid to spin. In this case, the rotating magnetic field is created with the two neodymium magnets and the fan.

This experiment involves minor electrical knowledge and uses neodymium magnets, so it should be conducted only by adults with necessary safety measures taken.

Supplies

• Laptop fan
• A way to power the fan (i.e. a power adapter,batteries)
• Neodymium magnets
• Flat surface to cover the fan
• Plastic or nonferrous box
• Bar magnet (specialty coated to prevent corrosion)

or

• Encase magnets with moldable plastic

Steps

1. Glue two neodymium magnet discs to the hub of the fan, making sure that they are spaced evenly on opposites.
2. In order to power the fan, it needs some sort of power source or connector. There are various ways of doing this. One of the common ways is by taking the red and black wires from the computer fan and connecting them to a battery.
3. Place the computer fan and power source in a square shaped nonmagnetic box a little bigger than the fan. Its height should rise above the neodymium magnets. About ¼ inch is ample enough to leave space for a flat surface.
4. Put a flat nonferrous lid on top of the box, concealing the fan inside. If the box has no lid, you can make one by gluing or screwing on plastic or plexiglass.
5. Test out your magnetic stirrer by putting in your magnetic stir bar (coated bar magnet) in a beaker and pouring in water. You can also make your own stir bar by coating magnets in moldable plastic. When you turn the fan on, the magnets on the fan hub will cause the magnetic stirrer to spin and stir the water.

This is just one version of a magnetic stirrer and it can be perfect for science enthusiasts or chemistry or biology students  that are on a tight budget. You can customize this DIY stirrer into a version that suits your needs. For magnet questions feel free to comment or contact us!

Photo by Laurence Livermore