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AN OVERVIEW OF RECENT DEVELOPMENTS IN NANOTECHNOLOGY FOR SPACE SYSTEMS.
WHY NANOTECHNOLOGY?
Advanced miniaturization, a key thrust area to enable new science and exploration missions
Ultrasmall sensors, power sources, communication, navigation,and propulsion systems with very low mass, volume and power consumption are needed.
Nanotechnology presents a whole new spectrum of opportunities to build device components and systems for entirely new space architecture.
Collection of microspacecraft making a variety of measurements.
RESEARCH FOCUS
Nanostructured thin films for infrared sensors.
Carbon nanotubes
Nanotubes- reinforced polymers.
Nanostructured chemical sensors
Graphene
Inorganic nanowires.
CARBON NANOTUBES
CNT is a tubular form of carbon with diameter as small as 1 nm.
Length: few nm to microns.
CNT is configurationally equivalent to a two dimensional graphene sheet rolled into a tube.
Carbon nanotubes materials possess the chemical properties of carbon, the thermal conductivity of diamond, and the electrical conductivity of copper or silicon.
CNT PROPERTIES
The strongest and most flexible molecular material because of C-C covalent bonding .
Young’s modulus of over 1 TPa vs 70 GPa for Aluminum, 700 GPA for C-fiber
strength to weight ratio 500 time > for Al; similar improvements over steel and titanium; one order of magnitude improvement over graphite/epoxy
Maximum strain ~10% much higher than any material.
Electrical conductivity six orders of magnitude higher than copper
Very high current carrying capacity
Excellent field emitter
CNT APLICATIONS
CNT based microscopy: AFM, STM…
Nanotube sensors: force, pressure, chemical…
Biosensors
Molecular gears, motors, actuators
Batteries, Fuel Cells: H2, Li storage
Nanoscale reactors, ion channels
Biomedical CNT quantum wire interconnects
Diodes and transistors for computing
Capacitors
Data Storage
Atomic Force Microscopy is a powerful technique for imaging, nanomanipulation, as platform for sensor work, nanolithography...
Conventional silicon or tungsten tips wear out quickly.
CNT tip is robust, offers amazing resolution.
NANOTUBE REINFORCED POLYMERS
Qualities such as electrical conductivity, high aspect ratio, high modulus, and high strength make carbon nanotubes a natural candidate for use as fillers in polymer composites for spacecraft structures.
The material—a carbon-nanotube/polyimide blend provides bulk conductivity and environmental stability to mitigate surface charging on satellites.
The addition of carbon nanotubes (0.54 percent by volume) to polycyanurate composite thin films increased the elastic modulus from 303,400 to 690,000 pounds per square inch (psi) a 127 percent increase.
NANOSTRUCTUREDTHIN FILMS FOR INFRARED SENSORS
Space systems rely on sophisticated sensors for numerous military and intelligence applications, including surveillance, target tracking and discrimination. Current sensor systems generally must be cooled to ultralow temperatures to enhance operating stability and resolution . However, cryogenically cooled devices present significant design challenges related to size, weight, power, and cost, as they are expensive to manufacture, require frequent calibration and maintenance, and consume appreciable amounts of power.
Infrared detectors made from pyroelectric materials (which generate a temporary electrical current in response to a change in temperature) have received significant attention as a result of their stability, sensitivity, wide spectral response, and low amount of dark current. In a pyroelectric detector, a ferroelectric absorbing layer is used to capture radiant energy, which heats up the pyroelectric material, causing a spontaneous and reversible electric polarization and a measurable variation in the surface charge.
BIOSENSORS
Our interest is to develop sensors for astrobiology to study origins of life. CNT, though inert,can be functionalized at the tip with a probe molecule. Current study uses AFM as an experimental platform.
The technology is also being used in collaboration with NCI to develop sensors for cancer diagnostics
Identified probe molecule that will serve as signature of leukemia cells, to be attached to CNT
Current flow due to hybridization will be through CNT electrode to an IC chip.
FEATURES
High specificity
Direct, fast response
High sensitivity
Single molecule and cell signal capture.
CHEMICAL SENSORS
Every atom in a single-walled nanotube (SWNT) is on the surface and exposed to environment .
Charge transfer or small changes in the charge-environment of a nanotube can cause drastic changes to its electrical properties
NANOWIRES
Motivations for selecting Single Crystall
Low defect density, grain boundary free .Well-defined surface structural properties
 Enhanced interfacial engineering
Predictable electron transport properties
 Predictable device performance
Unique physical properties due to quantum confinement effects
 Enhancement in device characteristics
Tunable electronic properties by doping
 Enhancement in device characteristics
Truly bottom-up integration approach
 Innovative fabrication schemes
Potential to revolutionize nano-scale science and technology
PROTEIN NANOTUBES
Heat shock protein (HSP 60) in organisms living at high temperatures
(“extremophiles”) is of interest in astrobiology
HSP 60 can be purified from cells as a double-ring structure consisting of 16-18 subunits. The double rings can be induced to self-assemble into nanotubes.
GRAPHENE
Aerospace has also begun to investigate graphene as a material for advanced applications. Graphene is a two-dimensional sheet of graphite (a carbon allotrope) with a thickness of one atomic layer. . Many labs have now isolated graphene flakes, and measurements show the material has phenomenal electrical properties.
The high mobility of charge carriers has many potential applications for molecular electronic devices such as room-temperature ballistic transistors and solar cells. The extremely high conductivity has also led to applications in the realm of chemical sensors—a device based on graphene was recently shown to achieve single molecule sensitivity.
One of the limitations of working with graphene is the preparation method. The technique looks no more sophisticated than drawing with a piece of graphite and repeatedly peeling it with adhesive tape until the thinnest flakes are found.
Aerospace researchers have succeeded in producing single layers of graphene and transferring them to silicon wafers for characterization and device fabrication. Applications could include sensors, electronic devices, batteries, and solar cells