Disclosed are techniques such as roll to roll processing to produce membrane valves in microelectromechanical systems that are integrated with micro-pumps that include a pump body having compartmentalized pump chambers. One application of this technology is as a valve assembly for a gas concentrator that includes a first micro pump for feeding an input gas stream, a second micro pump to supplying a vacuum and at least one sieve bed having a zeolite. The gas concentrator uses the valve assembly for controlling entry of gas from the first micro pump into the sieve bed and the second micro pump to vent.