Operation of pneumatically-actuated membrane-based microdevices for in situ analysis of extraterrestrial organic molecules after prolonged storage and in multiple orientations with respect to Earth's gravitational field

Pneumatically-actuated monolithic membrane microvalves are powerful microfluidic tools that can be integrated into programmable microfluidic architectures (PMAs) for multiple portable chemical analysis applications, including point-of-care (POC) diagnostics, environmental science, space exploration, etc…. However, these systems have not seen wide-scale deployment in industry or spaceflight due in part to (1) a concern that these systems may have a limited shelf-life and (2) a concern that performance depends on specific device orientation in a gravitational field. To address these concerns, we functionally tested a Mars Organic Analyzer microdevice fabricated in 2005 after 10 years of storage under ambient conditions. Using a square wave with a 500 millisecond (ms) actuation pulse width and a 1000 ms period and operating under vacuum at −980 millibar (mbar) from ambient pressure, all pneumatically-actuated valves opened in less than 1 h. The vacuum required to actuate an open valve ranged from −218 to −175 mbar from ambient pressure. The microvalves were then programmed to transfer fluid through the microdevice for flow rate characterization. Fluidic transfer occurred at a flow rate of 122 ± 8 microliters/minute (μL/min) right-side up in Earth's gravitational field and 114 ± 14 μL/min upside down in Earth's gravitational field, indicating likely successful implementation in an orbital microgravity environment. This demonstration that microdevices retain full functionality after over 10 years of storage combined with successful operation in multiple orientations in Earth's gravitational field further validates the value of microdevices based on these microvalves for fluidic manipulation and sample handling in outer planetary missions.