JPL has developed high performance cold cathodes using arrays of carbon nanotube bundles that produce > 15
A/cm2 at applied fields of 5 to 8 V/μm without any beam focusing. They have exhibited robust operation in poor
vacuums of 10-6 to 10-4 Torr- a typically achievable range inside hermetically sealed microcavities. Using these
CNT cathodes JPL has developed miniature X-ray tubes capable of delivering sufficient photon flux at acceleration
voltages of <20kV to perform definitive mineralogy on planetary surfaces; mass ionizers that offer two orders of
magnitude power savings, and S/N ratio better by a factor of five over conventional ionizers. JPL has also
developed a new class of programmable logic gates using CNT vacuum electronics potentially for Venus in situ
missions and defense applications. These "digital" vacuum electronic devices are inherently high-temperature
tolerant and radiation insensitive. Device design, fabrication and DC switching operation at temperatures up to
700° C are presented in this paper.
JPL has developed high performance cold cathodes using arrays of carbon nanotube bundles that routinely produce > 15 A/cm2 at
applied fields of 5 to 8 V/μm without any beam focusing. They have exhibited robust operation in poor vacuums of 10-6 to 10-4
Torr- a typically achievable range inside hermetically sealed microcavities. A new double-SOI process to monolithically integrate
gate and additional beam tailoring electrodes has been developed. These electrodes are designed according to application
requirements making carbon nanotube field emission sources application specific (Application Specific electrode-Integrated
Nanotube Cathodes or ASINCs). ASINCs, vacuum packaged using COTS parts and a reflow bonding process, when tested after 6-month shelf life have shown little emission degradation. Lifetime of ASINCs is found to be affected by two effects- a gradual
decay of emission due to anode sputtering, and dislodging of CNT bundles at high fields (> 10 V/μm). Using ASINCs miniature X-ray
tubes and mass ionizers have been developed for future XRD/XRF and miniature mass spectrometer instruments for lander
missions to Venus, Mars, Titan, and other planetary bodies.
There is a need for ever-larger apertures for use in space based optical imaging systems. Requirements on optical
instrumentation for future observations in space will place rigorous demands on wavefront quality. The design of
such mirrors involves a balance between the utilization of ultra-lightweight mirror and support structures, and the
active correction of the increased deformations due to these compromises in structural rigidity. Performing
wavefront control with a primary mirror requires precision and stability over a large structure. The wavefront
correction, therefore, can be partitioned in spatial frequency between the primary mirror and a tertiary deformable
mirror (DM). To realize the full potential of new ultra-lightweight, active primary mirror, the large-stroke
microactuator and DM technologies need to be developed. This paper presents a set of candidate components: linear
microactuator technology and a piezoelectric unimorph-based large-stroke DM technology, in the context of a
lightweight active mirror concept.
NASA's planetary exploration strategy is primarily targeted to the detection of extant or extinct signs of life. Thus, the agency is moving towards more in-situ landed missions as evidenced by the recent, successful demonstration of twin Mars Exploration Rovers. Also, future robotic exploration platforms are expected to evolve towards sophisticated analytical laboratories composed of multi-instrument suites. MEMS technology is very attractive for in-situ planetary exploration because of the promise of a diverse and capable set of advanced, low mass and low-power devices and instruments. At JPL, we are exploiting this diversity of MEMS for the development of a new class of miniaturized instruments for planetary exploration. In particular, two examples of this approach are the development of an Electron Luminescence X-ray Spectrometer (ELXS), and a Force-Detected Nuclear Magnetic Resonance (FDNMR) Spectrometer. The ELXS is a compact (< 1 kg) electron-beam based microinstrument that can determine the chemical composition of samples in air via electron-excited x-ray fluorescence and cathodoluminescence. The enabling technology is a 200-nm-thick, MEMS-fabricated silicon nitride membrane that encapsulates the evacuated electron column while yet being thin enough to allow electron transmission into the ambient atmosphere. The MEMS FDNMR spectrometer, at 2-mm diameter, will be the smallest NMR spectrometer in the world. The significant innovation in this technology is the ability to immerse the sample in a homogenous, uniform magnetic field required for high-resolution NMR spectroscopy. The NMR signal is detected using the principle of modulated dipole-dipole interaction between the sample's nuclear magnetic moment and a 60-micron-diameter detector magnet. Finally, the future development path for both of these technologies, culminating ultimately in infusion into space missions, is discussed.
This paper describes design, fabrication and characterization of a proof-of-concept vertical travel linear microactuator designed to provide out-of-plane actuation for high precision positioning applications in space. The microactuator is designed to achieve vertical actuation travel by incorporating compliant beam structures within a SOI (Silicon on Insulator) wafer. Device structure except for the piezoelectric actuator is fabricated on the SOI wafer using Deep Reactive Ion Etch (DRIE) process. Incremental travel distance of the piezoelectric actuator is adjustable at nanometer level by controlling voltage. Bistable beam geometry is employed to minimize initial gaps between electrodes. The footprint of an actuator is approximately 2 mm x 4 mm. Actuation is characterized with LabVIEW-based test bed. Actuation voltage sequence is generated by the LabVIEW controlled power relays. Vertical actuation in the range of 500 nm over 10-cycle was observed using WYKO RST Plus Optical Profiler.
A bulk micromachining process for fabricating extremely high aspect ratio metal structures is developed. The structures are thin films perpendicular to the plane of the substrate. The metal structures offer various physical and chemical properties depending on the choice of the metal used. Internal stress considerations for the choice of metal are also discussed.