0. A Medela breast pump can cost more than $200 dollars. The most expensive parts are the vacuum pump and the control electronics. The following may be a much cheaper alternative setup. I still need bottles, shields and tubings, but they are inexpensive.
1. Source of vacuum -- aspirator pump. It should be connected to the faucet.
The solenoid valve controls the on/off of vacuum. It's period is determined by potentiometers connected to a 555 timer.