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The purpose of this white paper is to provide an overview to the NRC Decadal Survey Mars and Ocean Worlds Sub-Panels on thermal protection system (TPS) technologies required for future Mars and Titan exploration missions. It considers the capability of heritage TPS technology used by previous Mars and Titan missions. A prime conclusion is that there are important advances regarding the availability of forebody TPS therefore, we recommend that NASA invest in a cross-cutting technology program that focuses on development and sustainment of relevant TPS materials, entry systems, test facilities, design tools, and flight instrumentation.

The purpose of this white paper is to provide an overview to the NRC Decadal Survey Inner Planets Sub–Panel on key technologies required for future Venus exploration missions. It covers both heritage technologies and identifies new technologies to enable future missions in all three mission classes. The technologies will focus on mission enabling and enhancing capabilities for in situ missions, because most orbiter related sub–systems are considered heritage technologies. This white paper draws heavily on the recently completed Venus Flagship Mission study that identified key technologies required to implement its Design Reference Mission and other important mission options. The highest priority technologies and capabilities for the Venus Flagship Design Reference mission consist of: surface sample acquisition and handling; mechanical implementation of a rotating pressure vessel; a rugged–terrain landing system; and a large scale environmental test chamber to test these technologies under relevant Venus–like conditions. Other longer–term Venus Flagship Mission options will require additional new capabilities, namely a Venus–specific Radioisotope Power System; active refrigeration, high temperature electronics and advanced thermal insulation. The white paper will also argue for a technology development program, since without it future Venus missions might not be achievable.

On September 12th, 2018, a sounding rocket flight test was conducted on a mechanically-deployed atmospheric entry system known as the Adaptable Deployable Entry and Placement Technology (ADEPT). The purpose of the Sounding Rocket One (SR-1) test was to gather critical flight data for evaluating the vehicle's in-space deployment performance and supersonic stability. This flight test was a major milestone in a technology development campaign for Nano-ADEPT: the application of ADEPT for small secondary payloads. The test was conducted above White Sands Missile Range, New Mexico on a SpaceLoft XL rocket manufactured by UP Aerospace. This paper describes the system components, hardware development campaign, test execution, and test conclusions.

The Adaptive Deployable Entry and Placement Technology (ADEPT) is being considered as an entry, descent and landing (EDL) system to enable Human Mars class missions. ADEPT is a mechanically deployable decelerator that makes use of a 3 d woven carbon fabric as both heat shield and primary structure. The Human Mars Mission design study is focused, in part, on assessing the viability of ADEPT and identifying technical challenges, operational constraints, and critical risk mitigation activities. Study inputs included definition of the ground rules and assumptions, associated mission timelines and high level functional requirements. These inputs enabled the clarification of the concept of operations along with the design constraints and environments. Subsystem trades, mass sizing and integrated flight performance assessments enabled determination of a feasible mission architecture. Key outputs from the design study include a parametric mass model, driving requirements, key performance parameters and critical risks. These findings enable us to determine strategies for technical maturation and risk mitigation that can be assessed against resource and programmatic constraints to aid in advanced planning for human exploration of Mars.

The Adaptable, Deployable Entry and Placement Technology (ADEPT) architecture represents a novel approach for entry vehicle design utilizing a high performance carbon-fabric to serve as the primary drag surface of the mechanically deployed decelerator. The ADEPT project team is advancing this decelerator technology via systems-level testing at the one-meter diameter (nano-ADEPT) scale. A subsonic aeroloads test (May 2015) and an arc-jet aeroheating test (Sept 2015) have already been completed. The initial system-level development of the nano-ADEPT architecture will culminate in the launch of a 0.7 meter deployed diameter ADEPT sounding rocket flight experiment named, SR-1. Launch is planned for August 2017. The test will utilize the NASA Flight Opportunities Program sounding rocket platform provided by UP Aerospace to launch SR-1 to an apogee over 100 km and achieve re-entry conditions with a peak velocity near Mach 3. The SR-1 flight experiment will demonstrate most of the primary end-to-end mission stages including: launch in a stowed configuration, separation and deployment in exo-atmospheric conditions, and passive ballistic re-entry of a 70-degree half-angle faceted cone geometry. ADEPT SR-1 will determine supersonic through transonic aerodynamic stability of the unique ADEPT blunt body shape with an open-back entry vehicle configuration.

Thermal protection system materials for the Mars Science Laboratory mission were tested in the NASA Ames 60 MW arcjet in a shear environment. Shear tests were performed on candidate ablative heat shield materials in wedge and swept cylinder test fixtures. In portions of the expected flight environment, the proposed main heat shield material, known as SLA-561V, recessed orders of magnitude faster than predicted. An alternate main heat shield material, known as phenolic impregnated carbon ablator, behaved reasonably well in all regions of the flight envelope investigated here. However, the measured recession rate of the phenolic impregnated carbon ablator was on average 50% greater than the predicted recession by the fully implicit ablation and thermal response code, and in some cases the measured recession was as much as 150% greater (uncertainties included). Phenolic impregnated carbon ablator’s higher recession rate than predicted (in shear) resulted in adding thickness margin to the flight heat shield d...

Although horizontally-aligned carbon nanotube (HACNT) interconnects are the most common scenarios that have been modeled and analyzed in theoretical research, fabrication of HACNT test structures has remained an enigma until now. Through addressing several fabrication challenges, this paper reports a novel process that enables fabrication of high-density, long (over hundred microns), and thick (up to micrometer) HACNT interconnects. Furthermore, horizontal CNT-based 2-D Manhattan structure is demonstrated by properly designing the catalyst and flattening process. These structures are crucial for building angled interconnects and on-chip passive devices. In addition, to address the contact issue between metal and thick HACNT bundles, a multistep lithography combined with specifically designed metal deposition technique is performed to ensure full contact configuration. Using such a process, test structures with arrays of various sizes of HACNT bundle interconnects are fabricated. The process developed in this paper provides an important platform for future research and technology development of CNT-based interconnects and passive elements.

A wind tunnel test of the Adaptable Deployable Entry and Placement Technology (ADEPT) was conducted in April 2015 at the US Army's 7×10 Foot Wind Tunnel located at NASA Ames Research Center. Key geometric features of the fabric test article were a 0.7 m deployed base diameter, a 70° half-angle forebody cone angle, eight ribs, and a nose-to-base radius ratio of 0.7. The primary objective of this wind tunnel test was to obtain static deflected shape and pressure distributions while varying pretension at dynamic pressures and angles of attack relevant to entry conditions at Earth, Mars, and Venus. Other objectives included obtaining aerodynamic force and moment data and determining the presence and magnitude of any dynamic aeroelastic behavior (buzz/flutter) in the fabric trailing edge. All instrumentation systems worked as planned and a rich data set was obtained. This paper describes the test articles, instrumentation systems, data products, and test results. Four notable conclusions are drawn. First, test data support adopting a pre-tension lower bound of 10 lbf/in for Nano-ADEPT mission applications. Second, test results indicate that the fabric conditioning process needs to be reevaluated. Third, no flutter/buzz of the fabric was observed for any test condition and should also not occur at hypersonic speeds. Fourth, translating one of the gores caused ADEPT to generate lift without the need for a center of gravity offset. At hypersonic speeds, the lift generated by actuating ADEPT gores could be used for vehicle control.

We present temperature-dependent electrical characteristics of vertically aligned carbon nanofiber (CNF) arrays for on-chip interconnect applications. The study consists of three parts. First, the electron transport mechanisms in these structures are investigated using I-V measurements over a broad temperature range (4.4 K to 350 K). The measured resistivity in CNF arrays is modeled based on known graphite two-dimensional hopping electron conduction mechanism. The model is used because of the disordered graphite structure observed during high-resolution scanning transmission electron microscopy (STEM) of the CNF and CNF-metal interface. Second, electrical reliability measurements are performed at different temperatures to demonstrate the robust nature of CNFs for interconnect applications. Finally, some guidance in catalyst material selection is presented to improve the nanostructure of CNFs, making the morphology similar to multiwall nanotubes.

Small spacecraft have emerged in recent years from a niche academic pursuit to a platform for governments and corporations to perform scientific and commercial ventures in space at much lower cost. Simultaneously, the field of Entry, Descent, and Landing (EDL) is rapidly maturing a number of technologies geared toward delivering ever-larger payloads to destinations across our solar system, with the culminating event being safe transport of human beings to the surface of Mars. One of these technologies for landing large payloads, known as the Adaptable, Deployable Entry and Placement Technology (ADEPT), uses a mechanical skeleton to deploy a revolutionary carbon fabric system that serves as both heat shield and primary structure during atmospheric entry. This paper explores the application of a Nano-ADEPT entry system for delivery of very small payloads (< 5 kg) to locations of interest in an effort to leverage low-cost platforms to rapidly mature the technology while simultaneously delivering high-value science. It is shown that secondary payload missions to Mars as well as entry from low Earth orbit are feasible. Secondary payload missions to Venus at small scale present a greater challenge and may only be feasible if the system can be designed with exceptionally low mass. The technology maturation strategy for Nano-ADEPT is described. Four test campaigns underway at the time of writing are discussed in detail, including deployment testing, wind tunnel testing, system-level arc jet testing, and a sounding rocket flight test. To conclude, a mission opportunity is described to demonstrate Nano-ADEPT from the International Space Station.

The rapid development in nanomaterials and nanotechnologies has provided many new opportunities for electroanalysis. We review our recent results on the fabrication and electroanalytical applications of nanoelectrode arrays based on vertically aligned multi-walled carbon nanotubes (MWCNTs). A bottom-up approach is demonstrated, which is compatible with Si microfabrication processes. MWCNTs are encapsulated in SiO2 matrix leaving only the very end exposed to form inlaid nanoelectrode arrays. The electrical and electrochemical properties have been characterized, showing well-defined quasireversible nanoelectrode behavior. Ultrasensitive detection of small redox molecules in bulk solutions as well as immobilized at the MWCNT ends is demonstrated. A label-free affinity-based DNA sensor has shown extremely high sensitivity approaching that of fluorescence techniques. This platform can be integrated with microelectronics and microfluidics for fully automated microchips.

In this report, we show controlled in-situ doping of a single crystalline metal oxide nanowire, using indium-doped tin oxide (In−SnO2) as an example, during a heteroepitaxial growth process. Highly regular and high-density arrays of In−SnO2 nanowires, which demonstrate three- and four-fold growth symmetry, are obtained directly on optical sapphire substrates. Similar synthesis strategies, involving careful selection of desired growth conditions and smart manipulation of favorable thermodynamic properties, could be extended to production of various doped metal oxide nanowires.

Carbon nanotubes (CNTs), due to their unique electronic and extraordinary mechanical properties, have been receiving much attention for a wide variety of applications. Recently, plasma enhanced chemical vapour deposition (PECVD) has emerged as a key growth technique to produce vertically-aligned nanotubes. This paper reviews various plasma sources currently used in CNT growth, catalyst preparation and growth results. Since the technology is in its early stages, there is a general lack of understanding of growth mechanisms, the role of the plasma itself, and the identity of key species responsible for growth. This review is aimed at the low temperature plasma research community that has successfully addressed such issues, through plasma and surface diagnostics and modelling, in semiconductor processing and diamond thin film growth.

Hypersonic Inflatable Aerodynamic Decelerators (HIADs) have been identified as a key technology for descent and landing of large payloads on Mars and other planetary bodies. The reduction in ballistic coefficient of the entry vehicle, facilitated by the low mass increase in drag area, offers lower heating rates, greater payloads, and increased mission flexibility using existing boosters. Under NASA LaRC’s guidance and support Airborne Systems designed and built a series of test articles to validate the stacked tori concept through ground testing and ultimately in a highly successful flight test of the 3m Inflatable Re-entry Vehicle Experiment-3 (IRVE-3) configuration. Ground testing was conducted to validate and develop the concept for flight. Material, seam and joint, subsystem, and system tests were performed to validate the design and fabrication techniques. A flight load test was successfully conducted to demonstrate the structural and system integrity at flight-like aerodynamic loading conditions. Packaging tests were conducted to demonstrate the repeatable packaging and robustness required for efficient low volume launch retention and stowage. A series of deployment tests demonstrated the capability of all components to achieve the required flight geometry. FEA capability using LS-DYNA was developed in parallel and supported the design and test activities. A 6m configuration was designed and fabricated to demonstrate scalability of the stacked tori configuration. The 6m configuration was installed in the Ames National Full-Scale Aerodynamic Complex (NFAC) and tested at subsonic conditions. Though the Mach number and dynamic pressures were not representative of the mission flight conditions the data gathered was compared to predictions and used to validate the analysis techniques. NASA LaRC’s IRVE-3 mission and HIAD programs have done much to validate Airborne Systems braided AirBeam TM technology and the stacked tori configuration for used as a deployable heat shield and will pave the way for incorporation of this new technology into America’s space programs. Introduction A stacked tori inflatable decelerator is a pneumatically deployed heat shield designed to provide aerodynamic drag at high altitudes and Mach numbers to support the entry and descent of re-entry vehicles for terrestrial and interplanetary use. To date heat shields have been rigid structures sized to fit inside a booster shroud thus limiting the size and consequently drag area and mission flexibility. Stacked tori inflatable decelerators utilize inflatable structures that stow compactly for the boost and cruise portions of the mission then inflate on command to form a high strength aerodynamically stable conic structure able to withstand the high heating rates and structural loads upon contact with an atmosphere. Several papers have been written describing the advantages and applicability of 1 Program Manager, 3000 W. Segerstrom, Santa Ana, CA 92704, AIAA Senior Member 2 Analysis Manager, 3000 W Segerstrom, Santa Ana, CA 92704, AIAA Technical Chair 3 Chief Engineer, 3000 W. Segerstrom, Santa Ana, CA 92704, AIAA Senior Member 4 IRVE-3 Chief Engineer, Atmospheric Flight and Entry Systems Branch, NASA LaRC/MS489, AIAA Member 5 HIAD Aerospace Engineer, Atmospheric Flight and Entry Systems Branch, NASA LaRC/MS489, AIAA Member 6 Aerospace Engineer, Entry Systems and Vehicle Development Branch, NASA Ames Research Center, AIAA Member

In 2012, two large-scale models of a Hypersonic Inflatable Aerodynamic decelerator were tested in the National Full-Scale Aerodynamic Complex at NASA Ames Research Center. One of the objectives of this test was to measure model deflections under aerodynamic loading that approximated expected flight conditions. The measurements were acquired using stereo photogrammetry. Four pairs of stereo cameras were mounted inside the NFAC test section, each imaging a particular section of the HIAD. The views were then stitched together post-test to create a surface deformation profile. The data from the photogram- metry system will largely be used for comparisons to and refinement of Fluid Structure Interaction models. This paper describes how a commercial photogrammetry system was adapted to make the measurements and presents some preliminary results.

New Entry, Decent, and Landing (EDL) technologies are being explored to facilitate the landing of high mass vehicles. Current EDL technologies are limited due to mass and volume constraints dictated by launch vehicle fairings. Therefore, past and present technologies are now being considered to provide a mass and volume efficient solution, including Inflatable Aerodynamic Decelerators (IADs). To better define the instrumentation challenges posed by IAD technology development, a survey was conducted to identify valuable measurements for ground and flight testing of the flexible materials and structures used in their design. From this survey many sensing technologies and systems were explored specific to the stacked torus IAD, resulting in a down-selection to the most viable prospects. The majority of these systems, including wireless data acquisition, were then rapid prototyped and evaluated during component level testing to determine the best integration techniques specific to a 3m and 6m diameter stacked toroid IAD. Each sensing system was then integrated in support of the Hypersonic Inflatable Aerodynamic Decelerator ground test campaign. In this paper these IAD instrumentation systems are described along with their challenges in comparison to traditional rigid aeroshell systems. Requirements resulting from the survey are listed and instrumentation integration techniques and data acquisition are discussed.

The bottom-up fabrication and electrical properties of end-to-end contacted multiwalled carbon nanotube (MWCNT) heterojunctions are reported. The vertically aligned MWCNT heterojunction arrays are formed via successive plasma-enhanced chemical vapor deposition processing to achieve the layered junction architecture. Electron microscopy and current-sensing atomic force microscopy are used to reveal the physical nature of the junctions. Symmetric, nonlinear I–V curves of the as-fabricated junctions indicate that a tunnel barrier is formed between the end-to-end contacted MWCNTs. Repeated high bias I–V scans of many devices connected in parallel fuses the heterojunctions, as manifested by a shift to linear I–V characteristics.

The aeroelastic behavior of large-scale hypersonic inflatable aerodynamic decelerators (HIADs) will be investigated by wind tunnel testing to develop analysis and design tools and to advance scalable manufacturing and assembly technologies for inflatable aeroshells. Three stacked toroid, 60 degree halfangle sphere cone HIAD test articles of 3, 6 and 8.3 m in diameter will be tested in subsonic flow fields that produce flight-like aerodynamic loading. The test articles are assembled from inflatable torus segments composed of fiber reinforced thin films, which are joined together with high strength textile woven structural straps. A poly vinyl chloride coated structural fabric will be sewn together to produce an aerodynamic skin that covers the inflatable aeroshell structure. The inflatable aeroshell test articles will incorporate many flight-like design features including rigid centerbody interface attachment and load distributing strap arrangements. Each HIAD test article will be swept through +/- 25 degree yaw angles while varying the inflatable structure internal pressure and test section dynamic pressure. To correlate fluid structure interaction models full-field photogrammetry and surface pressure measurements will be used to characterize local and global aeroshell deformation and pressure distribution. The verification of fluid structure interaction models enables the establishment of baseline aeroelastic performance at relevant scales. This paper discusses the objectives, planning and limitations of testing large diameter HIADs in the National FullScale Aerodynamics Complex 40 x 80 foot test section. An overview of the design reference mission, test approach, test design, instrumentation and model verification is discussed.

Damage from Micrometeoroid and Orbital Debris (MMOD) impacts poses a substantial risk for the loss of crew for the currently planned CEV missions to the International Space Station (ISS). 1 2 The Columbia Space Shuttle accident in 2003 spurred an investigation that led to the requirement of an active impact monitoring system on the Shuttle Orbiter. The MMOD impact Damage Recording System (DRS) presents a reliable, mass- and power-efficient Thermal Protection System (TPS) impact detection system that can be readily integrated with manned and robotic spacecraft. Thus, the Crew Exploration Vehicle (CEV) is considering inclusion of active MMOD detection systems for monitoring damage to the backshell TPS.

Entry Systems will play a crucial role as NASA develops the technologies required for Human Mars Exploration. The Exploration Technology Development Program Office established the Entry, Descent and Landing (EDL) Technology Development Project to develop Thermal Protection System (TPS) materials for insertion into future Mars Entry Systems. An assessment of current entry system technologies identified significant opportunity to improve the current state of the art in thermal protection materials in order to enable landing of heavy mass (40 mT) payloads. To accomplish this goal, the EDL Project has outlined a framework to define, develop and model the thermal protection system material concepts required to allow for the human exploration of Mars via aerocapture followed by entry. Two primary classes of ablative materials are being developed: rigid and flexible. The rigid ablatives will be applied to the acreage of a 10x30 m rigid mid L/D Aeroshell to endure the dual pulse heating (peak approx.500 W/sq cm). Likewise, flexible ablative materials are being developed for 20-30 m diameter deployable aerodynamic decelerator entry systems that could endure dual pulse heating (peak aprrox.120 W/sq cm). A technology Roadmap is presented that will be used for facilitating the maturation of both the rigid and flexible ablative materials through application of decision metrics (requirements, key performance parameters, TRL definitions, and evaluation criteria) used to assess and advance the various candidate TPS material technologies.

Computational Fluid Dynamics (CFD) simulations of protruding gap fillers on the Mars Science Laboratory Heatshield were computed and compared to experimental data and engineering correlations. Based on these computations, an estimate of the heating augmentation as a function of a normalized height was developed. For a tall gap filler, where the protuberance’s height is greater than twice the boundary layer thickness, the heating augmentation downstream of the gap filler appears to reach a maximum value that is double the smooth surface heat flux. For shorter protuberances, a power law fit was developed based on the CFD solutions. Thermal material analysis using the augmentation curve fit indicates that the MSL heatshield should have sufficient margins to account for elevated heat loads caused by protruding gap fillers.

Dielectrophoresis (DEP) is an effective microelectronic technique for trapping and manipulating biological particles in a microfluidic environment, which relies on the highly asymmetric electric field gradient created by the microelectrodes. Here we demonstrate an AC DEP technique for single-bacteria trapping using nanoelectrode arrays (NEAs) in a "points-and-lid" configuration. The NEA is based on vertically aligned carbon nanofibers (CNFs) embedded in SiO2 matrix. The miniaturization of the electrode size provides a highly focused electric field with the gradient enhanced by several orders of magnitude. Finite element modeling indicated that the pDEP force using such NEA-based devices can be increased by over 100 times. Experiments indicated that the bacteria can be trapped instantaneously on to the exposed CNF tip with an AC voltage of ~3 Vpp. In most cases, a single E. coli bacterium is trapped at a single CNF site due to the screening effect. Such nano-DEP device allows the integration of millions of nanolectrodes deterministically in lab-on-a-chip devices that can be used for effective cell manipulating and concentration.

Deep brain stimulation (DBS, neuromodulation) has been developed over the last 15 years as an effective treatment for movement disorders such as Parkinson’s disease and essential tremor. DBS will likely prove effective for epilepsy, depression and other mood disorders, and eating disorders as well [1]. Current techniques for DBS utilize macroelectrodes (>1 mm diameter) which provide imprecise stimulation. In addition, the stimulation is open-loop (i.e. the stimulation is not guided by monitoring of brain electrical or neurochemical activity), which is not only wasteful (the stimulation is constant) but is also of suboptimal effectiveness. Marked improvement in DBS could be realized by combining continuous monitoring of neurotransmitter levels and electrical activity with precise electrical stimulation (electrochemical closed-loop neuromodulation). Most importantly, reducing the scale to the nano level (1) improves signal-to-noise ratios, (2) permits greater precision (down to the subnuclei level) and (3) allows multiple recording/monitoring and stimulation sites throughout the central nervous system (Fig 1) [2].

Scanning electron microscopy (SEM) for imaging the interface between carbon nanofibers (CNFs) and the underlying substrate is presented. By irradiating the electron beam perpendicular to the substrate, bright contrast is observed at the region where a small gap exists between the CNF and substrate. The energy-diameter diagram for the observation of the bright contrast is derived, which can be understood by using the theory of electron penetration into solid. Monte Carlo simulation is performed to reproduce the experimental observation based on our model, and the contrast sensitivity to the gap height is discussed.

We have used a microfabricated device to measure the thermal contact resistance between a 152-nm-diameter carbon nanofiber and the measurement device, and found that heat conduction models based on Fourier’s law can underestimate the thermal contact resistance at the nanoscale constriction if a large reduction in the effective thermal conductivity of the constriction is not taken into account. With the thermal contact resistance reduced by the deposition of a platinum layer on the contact, we observed that the thermal conductivity of the carbon nanofiber grown by using a plasma enhanced chemical vapor deposition method is comparable to that of graphite fibers grown by pyrolysis of natural gas prior to high-temperature heat treatment.Copyright © 2005 by ASME

Background: Reducing cost and time is the major concern in clinical diagnostics, particularly in molecular diagnostics. Miniaturization technologies have been recognized as promising solutions to provide low-cost microchips for diagnostics. With the recent advancement in nanotechnologies, it is possible to further improve detection sensitivity and simplify sample preparation by incorporating nanoscale elements in diagnostics devices. A fusion of micro- and nanotechnologies with biology has great potential for the development of low-cost disposable chips for rapid molecular analysis that can be carried out with simple handheld devices. Approach: Vertically aligned multiwalled carbon nanotubes (MWNTs) are fabricated on predeposited microelectrode pads and encapsulated in SiO2 dielectrics with only the very end exposed at the surface to form an inlaid nanoelectrode array (NEA). The NEA is used to collect the electrochemical signal associated with the target molecules binding to the probe molecules, which are covalently attached to the end of the MWNTs. Content: A 3 × 3 microelectrode array is presented to demonstrate the miniaturization and multiplexing capability. A randomly distributed MWNT NEA is fabricated on each microelectrode pad. Selective functionalization of the MWNT end with a specific oligonucleotide probe and passivation of the SiO2 surface with ethylene glycol moieties are discussed. Ru(bpy)2+-mediator-amplified guanine oxidation is used to directly measure the electrochemical signal associated with target molecules. Summary: The discussed MWNT NEAs have ultrahigh sensitivity in direct electrochemical detection of guanine bases in the nucleic acid target. Fewer than ∼1000 target nucleic acid molecules can be measured with a single microelectrode pad of ∼20 × 20 μm2, which approaches the detection limit of laser scanners in fluorescence-based DNA microarray techniques. MWNT NEAs can be easily integrated with microelectronic circuitry and microfluidics for development of a fully automated system for rapid molecular analysis with minimum cost.

State-of-the-art ICs for microprocessors routinely dissipate power densities on the order of 50 W/cm2. This large power is due to the localized heating of ICs operating at high frequencies, and must be managed for future high-frequency microelectronic applications. Our approach involves finding new and efficient thermally conductive materials. Exploiting carbon nanotube (CNT) films and composites for their superior axial thermal conductance properties has the potential for such an application requiring efficient heat transfer. In this work, we present thermal contact resistance measurement results for CNT and CNT-Cu composite films. It is shown that Cu-filled CNT arrays enhance thermal conductance when compared to as-grown CNT arrays. Furthermore, the CNT-Cu composite material provides a mechanically robust alternative to current IC packaging technology.

The authors present scanning transmission electron microscopy (STEM) of carbon nanofibers (CNFs) on a bulk substrate using conventional scanning electron microscopy (SEM) without specimen thinning. By utilizing the electron beam tilted >85° from the substrate normal, bright-field STEM contrast is obtained for the CNFs on substrate with conventional SEM. Analysis of the observed contrast using Monte Carlo simulation shows that the weakly scattered electrons transmitted from the CNF are selectively enhanced by the largely tilted substrate and result in the observed STEM contrast. This mechanism provides a useful STEM imaging technique to investigate the internal structure of materials on bulk substrates without destructive specimen thinning.

We present the contrast mechanisms of scanning electron microscopy (SEM) for visualizing the interface between carbon nanofibers (CNFs) and the underlying substrate. SEM imaging with electron beam energies higher than a certain threshold provides different image contrasts depending on whether CNFs are in contact with the substrate or suspended above the substrate. CNFs with diameters ranging from 25to250nm are examined with various electron beam energies. It is found that the threshold energy corresponds to the energy required to penetrate the CNF and its dependence on CNF diameter can be understood using the theory of electron range. This knowledge will be quite useful for interface imaging of all nanostructure devices.