Improved micro-extraction systems could be useful for military remote sensing using microfluidics.
Great strides are taken to miniaturize spaceflight instrumentation, particularly analytical systems such as liquid chromatographs, gas chromatographs, and mass spectrometers. With miniaturization of instruments, large amounts of samples are no longer required. Therefore, a lesser quantity of sample from the environment needs to be acquired and extracted. Current practices of sample extraction are large in volume and consume an enormous amount of power, which is inconsistent for microfluidic instruments in development. These consume minute amounts of power and are of low mass. There have been efforts to create micro-sample extraction systems; however, a downfall of those systems is the inability to automatically close sample reservoirs.
The Micro-Lid (Lid) creates a lid structure that can be actuated “open” to allow samples from an icy body to be inserted into a sample reservoir, then actuated “close” to trap the samples within the sample reservoir. This Micro-Lid allows further development of Goddard Space Flight Center's micro-extraction systems that will enable further miniaturization of micro-analytical systems, creating a suite of Lab-On-A-Chip devices — more commonly known as Lab-On-A-Tea-Cup. Enabling the Micro-Lid aids in-situ planetary exploration of primitive bodies and outer planet satellites. Fabrication is completed using typical microelectromechanical systems (MEMS) microfabrication processes.
Micro-Lid consists of a bilayer cantilever that is thermally actuated, thereby functioning as a thermal bimetallic actuator. The bilayer cantilever is composed of two metals, each with significantly different coefficients of thermal expansion (CTE). Upon application of heat, one metal expands more than the other, allowing the cantilever to bend. This heating action, along with the CTE mismatch, is what enables the Micro-Lid to lift and open the door for a micro-sample extraction system. With the lid open, sample would be inserted into the reservoir; thereafter, the heat is turned off and the lid closes, sealing the sample reservoir. For leak-tight seals or hermetic seals, solder is placed at the base of the lid and is then melted. When melted, the seal is leak-tight.
Fabrication of the Micro-Lid is conducted within a Class 100 cleanroom using MEMS processes. Current bimetallic materials used for actuation are Invar-Aluminum and Tungsten-Aluminum. With a change in temperature, the bimetallic actuator bends and raises the silicon lid. The heat provided for the thermal actuation is generated by creating a heater out of the Invar in the Invar-Aluminum bimetallic, or Tungsten in the Tungsten-Aluminum bimetallic.