Microvalve array fabrication using selective PDMS (polydimethylsiloxane) bonding through Perfluorooctyl-trichlorosilane passivation for long-term space exploration

Integrated high performance microfluidic organic analysis instrument for planetary and space exploration

The exploration of our solar system to characterize the molecular organic inventory will enable the identification of potentially habitable regions and initiate the search for biosignatures of extraterrestrial life. However, it is challenging to perform the required high-resolution, high-sensitivity chemical analyses in space and in planetary environments. To address this challenge, we have developed a microfluidic organic analyzer (MOA) instrument that consists of a multilayer programmable microfluidic analyzer (PMA) for fluidic processing at the microliter scale coupled with a microfabricated glass capillary electrophoresis (CE) wafer for separation and analysis of the sample components. Organic analytes are labeled with a functional group-specific (e.g. amine, organic acid, aldehyde) fluorescent dye, separated according to charge and hydrodynamic size by capillary electrophoresis (CE), and detected with picomolar limit of detection (LOD) using laser-induced fluorescence (LIF). Our goal is a sensitive automated instrument and autonomous process that enables sample-in to data-out performance in a flight capable format. We present here the design, fabrication, and operation of a technology development unit (TDU) that meets these design goals with a core mass of 3 kg and a volume of <5 L. MOA has a demonstrated resolution of 2 × 105 theoretical plates for relevant amino acids using a 15 cm long CE channel and 467 V cm-1. The LOD of LIF surpasses 100 pM (0.01 ppb), enabling biosignature detection in harsh environments on Earth. MOA is ideally suited for probing biosignatures in potentially habitable destinations on icy moons such as Europa and Enceladus, and on Mars.

Self-Healing Transparent Poly(dimethyl)siloxane with Tunable Mechanical Properties: Toward Enhanced Aging Materials for Space Applications

When exposed to the geostationary orbit, polymeric materials tend to degrade on their surface due to the appearance of cracks. Implementing the self-healing concept in polymers going to space is a new approach to enhancing the lifespan of materials that cannot be replaced once launched. In this study, the elaboration of autonomous self-healing transparent poly(dimethylsiloxane) (PDMS) materials resistant to proton particles is presented. The PDMS materials are functionalized with various compositions of urea and imine moieties, forming dynamic covalent and/or supramolecular networks. The hydrogen bonds induced by the urea ensure the formation of a supramolecular network, while the dynamic covalent imine bonds are capable of undergoing exchange reactions. Materials with a broad range of mechanical properties were obtained depending on the composition and structure of the PDMS networks. As coating applications in a spatial environment were mainly targeted, the surface properties of the polymer are essential. Thus, percentages of scratch recovery were determined by AFM. From these data, self-healing kinetics were extracted and rationalized based on the polymer structures. The obtained data were in good agreement with the relaxation times determined by rheology in stress relaxation experiments. Moreover, the accelerated aging of materials under proton irradiation, simulating a major part of the geostationary environment, revealed a strong limitation or disappearance of cracks while keeping the transparency of the PDMS. These promising results open routes to prepare new flexible autonomous polymeric materials for space applications.

Optimization of Oligomer Stamping Technique for Normally Closed Elastomeric Valves on Glass Substrate

Microscale elastomeric valves are an integral part of many lab-on-chip applications. Normally closed valves require lower actuation pressures to form tight seals, making them ideal for portable devices. However, fabrication of normally closed valves is typically more difficult because the valve structure must be selectively bonded to its substrate. In this work, an oligomer stamping technique for selective bonding of normally closed valves is optimized for bonding of PDMS devices on glass substrates. Contact angle and blister bursting testing measurements are used to quantitatively characterize the oligomer stamping process for the first time, and recommendations are made for plasma treatment conditions, microstamping technique, and valve construction. Glass-PDMS devices are ideal for lab-on-chip systems that integrate electrodes on the rigid glass substrate. Here, integrated electrodes are used to assess valve performance, demonstrating electrical isolation in excess of 8 MΩ over the biologically relevant frequency range in the closed state. Further, electrical measurement is used to demonstrate that the valve design can operate under a pulsed actuation scheme, sealing to withstand fluid pressures in excess of 200 mbar.

Operation of a programmable microfluidic organic analyzer under microgravity conditions simulating space flight environments

A programmable microfluidic organic analyzer was developed for detecting life signatures beyond Earth and clinical monitoring of astronaut health. Extensive environmental tests, including various gravitational environments, are required to confirm the functionality of this analyzer and advance its overall Technology Readiness Level. This work examines how the programmable microfluidic analyzer performed under simulated Lunar, Martian, zero, and hypergravity conditions during a parabolic flight. We confirmed that the functionality of the programmable microfluidic analyzer was minimally affected by the significant changes in the gravitational field, thus paving the way for its use in a variety of space mission opportunities.

A simple and reliable microfabrication process for a programmable microvalve array

We describe our reliable methodology for fabricating a complex programmable microvalve array (PMA) and its integration with a glass microcapillary electrophoresis chip. This methodology is applicable to any device that requires multilayered PDMS, multiple alignment processes, selective PDMS bonding, and multilayered integration with downstream sensing systems. Along with the detailed step-by-step process, we discuss essential quality assurance checks that can be performed throughout fabrication to assist in troubleshooting and maximizing chip yield.•Comprehensive instructions for designing and fabricating a programmable microvalve array.•Selective bonding of PDMS and glass by microcontact printing.•Numerous quality control procedures to boost chip yield.