In case you need to create a monolayer of lipids inside a spherical flask and don’t to spend $3000 on a commercial rotary evaporator, this is the design you need. Justin Ingram and I set out to build such a device from things found around the lab for a small fraction of the cost.
The first step was to create a commutator that could support the flask and allow for the evacuation of the solvent vapors from the flask. We used a piece of Teflon coated stainless steel that was held in a piece of Delrin with a pair of Delrin spacers. We also used a planar ball bearing to lessen the friction between the stainless steel and the bushings. A piece of a 5ml syringe was attached to the other end of the tube and was then was covered in parafin. This piece was just the right size so as to fit into the opening of the spherical flask and be able to support its weight.
The next step was to provide the rotary action. We found a DC motor around the lab which was connected to a standard variable power supply. We transferred the force from the motor to the flask by a belt system implemented using a standard rubber band. Although the motor drew almost 1.5A while in operation, it did not get too hot over a period of half an hour. We are working on a thermocouple to allow us to attach a peltier device with a heat sink or just a heat sink to allow for more efficient cooling.
The main purpose of the vacuum system was to collect the solvent vapors, not to reduce the pressure inside the flask. For this reason, we were able to loosely connect a pair of luer-lok adapters together to allow for them to rotate and did not worry about the poor seal. We turned on the vacume system and verified that the vacuum was good enough to take in smoke from the surrounding area and assumed that it was sufficient. The vapors that we are working with are that harmful, but it is also possible to run this system inside of a fume hood. The commercial system also has a water-cooled condenser for collecting the solvent, but it is snowing outside, so we can put something out there to act as a low-cost condenser.
( evap-action.AVI )